Noticed my pedal was drifting ever so slowly to the floor, and thought 'uh oh'. Time to consider my next project, like now. Appears to be the original booster and master.

So at minimum, a master cylinder is in my future, then the "while you're in there bug" bit me.

A daunting number of choices out there, and follwing a good bit of 'thread search', wanted to pose this to the experts:

1) I don't track the car at all.
2) Running stock 15s, but with 8 and 10 wide wheels.
3) Prefer 'stock' apperance in the trunk compartment, though a minor deviation not bothersome.
4) As all of us, would prefer to spend $0, but can stomach up to $2grand done, so likely not able to get the 'big buck brake kit'.

Noticed sponsors offer bigger bore master cylinders, with what is claimed as 'superior flow' and 'better feel'.

All advice gladly accepted. Will stop driving the car til this is resolved.

Original Post

Once the proportioning valve (which is installed in the front circuit) is removed from the car the Pantera braked very well for the early 1970s era ... but it didn't brake very well after repeated stops because the disks were not ventillated ... the brakes would fade due to heat. There really isn't anything wrong with the performance of the brake system hydraulically outside of the proportioning valve being installed in the front circuit. The front brakes are decent assemblies with 4 piston calipers. The rear brake assemblies however are very undersized.

Is an oem style master available from Steve Wilkinson? If so, my advice would be to buy one, disassemble it before you install it in your car, clean it thoroughly, inspect the bores, lube the parts properly & re-assemble it, fill the master with fresh brake fluid and bench bleed it before you install it in your Pantera.

_______________________________________________
Minimum brake upgrade:

  • remove the proportioning valve from the hydraulic brake system entirely
  • replace the master cylinder with an oem style master cylinder
  • rebuild the front calipers
  • replace the front disks with ventillated disks
    (modified '65 - '67 Mustang disks)
  • front brake pads are available from EBC, Raybestos, JFZ, or Porterfield
    (I recommend ceramic pads for street cars)


amendment to list based on discussion in this thread:

  • replace the rear brake assemblies with the rear brake kit from SACC Restorations (the kit employs Wilwood 4 piston calipers).
  • retain the oem rear brake assemblies to use as parking brakes only. Parking brake options also include assemblies manufactured by IPSCO or Wilwood. SACC has a Pantera specific parking brake composed of Wilwood components.


_______________________________________________

The money you spend on this brake restoration & upgrade is guaranteed to be money well spent. You'll agree the first time you stop hard. The brakes shall feel "racier" and safer too. You'll enjoy the brakes the Pantera should have been equipped with in the first place. Its an invisble upgrade that won't detract from the original looks of your Pantera

Rock and Roll

-G

Hi Adams,

We can design a kit to upgrade as much or as little of the system as you wish (or your budget allows).

I completely agree with George that there is nothing wrong with the original hydraulics on the car after removing the stock proportioning valve.

We offer a complete brake upgrade for 15 inch wheels that includes 12.19 inch rotors. Drill, Slotted and Vented with a great looking black e-coating that gets removed immediately upon brake in. This gives a great contrast while providing rust protection on the non-contact areas of the rotors. That kit can be viewed at: http://pantera.saccrestorations.net/sak2001.html

Another option is simply upgrading just the rears. My recommendation is to go with the kit that provides a balanced system designed to work with the stock Pantera Master Cylinder. Our kits are all computer designed and track tested.

Take care, Scott
What are you looking to upgrade? Just Calipers? Would you like to upgrade just the rears? We can provide a kit designed for your needs.

I am not clear on what you are looking to accomplish? Are you only looking for a hydraulics upgrade?

The lowest cost and biggest bang for the buck, for a brake upgrade, is to remove the proportioning valve and then upgrade the rears to a 4 piston setup. Those 2 items alone will provide an unbelievable upgrade over stock!
I agree. Take the proportioning valve out. Why the factory felt they needed it is beyond me.
It is one strange Alien device.
I almost can see Dan Akroid with his Conehead makeup on saying that he was French being the engineer in charge, in between consuming mass quantities of beer that is?
Hum. A second thought was maybe it was Alejandro? He said he was from Argentina, but can he prove that? LOL.
quote:
Originally posted by Cowboy from Hell:
Picture 2. This proportioning valve (yellow arrow) is a little different configuration. But its in the same general place in the trunk.


I guess no one noticed the maxed out (1-1/2") pedal plate spacer on the foot box on this car did they? I did. I can't stand it when someone takes my advice?

Look closely. You will see the joint in the truck lining material and how close it is to the edge of the battery box cover. Big Grin
You can modify the proportioning valve to be nothing more then a pass through device so you don't have to worry about fittings etc...

You remove the valve, open it up and remove the part that regulates the pressure. It then becomes a non-functioning proportioning valve and you reinstall it and you're done...
quote:
Originally posted by Z06 Pantera:
You can modify the proportioning valve to be nothing more then a pass through device so you don't have to worry about fittings etc...

You remove the valve, open it up and remove the part that regulates the pressure. It then becomes a non-functioning proportioning valve and you reinstall it and you're done...


Simple solution. Still looks stock. Like I'm making money over here... to save up for some REAL BRAKES!

Thanks Scott, very much.
I used a parts-store Amercian-thread T-fitting and put on matching fittings w/ a double-flaring tool from the same store (cheapo import junk, not the $70 quality one) - it all works fine and you will only be spending about $25 total for tool, fittings, and T.
I'm going to redo my brakes also, but not sure removing the proportioning valve entirely is such good idea. Possibly replace it with a new adjustable one?

Usually the proportioning valve is put in to stop the rear tires from locking up before the fronts lock. Imagine you're hauling buns in a sweeping corner at 60 mph or higher, you hit the brakes hard, if the rear circuit gets too much pressure because you removed the proportioning valve the system lockups up the rear tires before the fronts, losing traction, sending the car into a spin. At least that's what the proportioning valve was supposed to do I thought. I had one of the McLaren Can Am cars and remember spending a lot of effort making sure the front and rear brake bias locked the fronts first, leaving the rears still turning.

Maybe if you are running 335's in the rear and 225's in front you have so much rubber on the ground in the rear that the brakes won't lock the rears before the fronts...but normally that what most manufactures do. I had a Fiat Spider in college that had a variable proportioning valve that was actuated by lift in the rear of the car...as you hit the brakes and the front of the car would squat(planting the front tires giving more traction) and the rear would start to rise(giving less traction), the proportioning valve would gradually lessen the rear pressure to stop the locking of the rear tires.

I have heard from Steve Wilkinson that he sells a 1" master that gives the brake system a much better feel with stock calipers.
Tom,

The stock proportioning valve in the Pantera reduced the line pressure to the front calipers, not to the rears.

quote:
I have heard from Steve Wilkinson that he sells a 1" master that gives the brake system a much better feel with stock calipers.

An increase in master cylinder bore will result in less pedal travel ("better feel"), and an increase in pedal effort (as in push harder).

John
quote:
Originally posted by Tom@Seal Beach:

Usually the proportioning valve is put in to stop the rear tires from locking up before the fronts lock.



That's correct.

If the rear tires don't lock-up with pressure to the front brakes reduced by a proportioning valve, there is no way they will lock up with full pressure applied to the front brakes by removal of the proportioning valve. The balance of braking front to rear moves more to the front when the proportioning valve is removed.

Removal of the proportioning valve is one of the oldest traditional mods to the Pantera, its a proven mod that has been performed for 40 years. Its nothing new, controversial, or dangerous. That's why vendors like Wilkinson have kits for performing the mod. Full pressure can be applied to the front brakes, allowing it to stop more quickly, with more stopping power. The braking performance (and therefore the safety) of your Pantera is enhanced by the proportioning valve's removal. Lots of owners have performed the mod, if you search the forum you'll find many recommendations for performing it, you won't find one complaint or horror story.

My Pantera has a Wilwood system. 12.75" rotors at all 4 corners, 4 piston calipers at all 4 corners, same size pads & pad material at all 4 corners. But the caliper pistons are smaller in the rear, only 65% of the piston area as the front. It has no proportioning valve, but it performs perfectly. I have flogged the car at over 100 mph on mountain roads, performed emergency stops, I've tried to make the rears lock up, but they never have. Brake systems don't necessarily "need" proprtioning valves. The Pantera's oem rear brakes are so undersized compared to the front brakes there is no way they will lock-up before the fronts.

-G
I am no expert and don't want to get into an all out argument, but there is a growing population that now does not advocate the removal of the proportioning valve.

As stated the Pantera valve is in the front brakes. More traditionally a proportioning valve would be in the rear braking system, to limit rear braking so the rears cannot lock before the fronts. However the Pantera front application is key to why it should be left alone in a stock braking system.

As G says the Pantera rear brakes are undersized in comparison to the front, the proportioning valve was inserted to compensate (limit) the front braking power to be more in line with the rear i.e. a matched system. When you remove that limitation front braking efficiency increases and yes the brakes feel better from a pedal persepctive, but you effectively now have two wheel braking as there is no restriction and all the stopping power is to the front brakes, you'll never ever lock up the rears because there is now close to zero rear braking efficiency. That is not a good scenario, the measure should not be just not locking up the rears, a good braking system should lock up the rears but just after the fronts.

Just my 2 cents
Julian
quote:
the measure should not be just not locking up the rears, a good braking system should lock up the rears but just after the fronts.


I think for the most part we are all in agreement. Removing the proportioning valve alone (without making an improvement in the rear) may not be a good idea. BUT, with the rears improved the proportioning valve SHOULD be removed.

It is all about balance. Every car should be evaluated based on it own configuration (weight distribution, tire size, etc...)

When we decided to get into brakes be did A LOT of testing to backup what most are saying here. Some people forget that the proportioning valve is in the front circuit on a Pantera.

Bottom line is a balanced system will not require a proportioning valve. The quickest and cheapest method for a stock Pantera brake system upgrade is to remove the proportioning valve and upgrade the rear brakes. It is amazing how this inexpensive change provides dramatic results.

Scott
quote:


Originally posted by Joules5:

there is a growing population that now does not advocate the removal of the proportioning valve.



Growing population sounds like a nice way to give more weight to the opinion of a few people.

It appears this "growing population" advocates retention of the proportioning valve based on a theory. A "real" problem caused by its removal was not mentioned, the theory is leaving it in results in better balance. I'd like to rephrase that theory if I may. "The rear brakes are inadequate, so we should reduce the effectiveness of the front brakes so they are more balanced with the rears". But guys ... making the front brakes less powerful means less braking performance! Which is better, two inadequate brakes, or four inadequate brakes?

Removing the proportioning valve measurably shortens the braking distances. That's why owners have been doing it for 40 years. Control while braking is not compromised either. It does not create a two wheel braking situation, the pressure to the rear circuit doesn't change, and the weight on the rear wheels remains the same. The rears are braking just as hard either way. If balanced braking means longer braking distances, then I choose more powerful braking over better balanced braking.

Reducing the power of the front circuit to "balance" the braking front to rear is going about it the wrong way! Wouldn't it be better to increase the power of the rear circuit? I may well agree with Chris that a rear brake upgrade will improve the Pantera's braking performance, but I am not in agreement that removal of the proportioning valve without a rear brake upgrade is a bad idea. I can't go that far Chris.

-G
quote:
I am not in agreement that removal of the proportioning valve without a rear brake upgrade is a bad idea. I can't go that far Chris.


I actually agree with you completely George. Notice how I said "May not be a good idea". With it's removal the rears are braking the same as before. As you said, the fronts are simply improved. How can anyone argue that an improvement in front brake performance is a bad thing... Smiler
My two cents.

How can it be a bad idea to have the best brakes one can in a car?
You would put the best tires, and engine that you can afford in. Why not brakes to?

For the time, the brakes new were nothing more then adequate.

Why Detomaso was married to the rear configuration is beyond me. It makes no sense except for production cost reasons.
I interpret the front proportioning valve as an attempt to cover up the inadequacy of the rear.

Just like it costs money to go fast and some say how fast can you afford to go, it isn't cheap to do brakes either.

Depending on the criteria controlled by the cars owner, such as wheels and tires, there are going to be a lot of options for brakes.

Some have tried to package a brake system at a reasonable cost that has been engineered to a degree and is ready to bolt on with no trial and error. That's great.

Probably everyone is going to have a critique of them in one form or another?

The only thing really that we can agree upon on brakes is that there are options and you don't have to stay with the stock system.

I think virtually all responsibly engineered replacement systems available now are going to be superior to the original.

For me, the only question is how much I can afford to spend on brakes since I feel strongly that the originals on my car must be upgraded in some significant way soon.
Like I said I'm no expert, but I as one of a "few people" voicing an opinion would be interested to see some skid pad testing in wet & dry conditions to see how overall braking is affected. I suspect that the seat of the pants evaluation has typically involved stomping on the brakes in a straight line on a dry road. Maybe that is okay as most Pantera's don't see a wet road ever anyway.

We are all in agreement that upgraded and balanced brakes are ultimately the answer. Replacing the proportioning valve with a modern adjustable one would likely be a good compromise with stock calipers IMO.

Julian
quote:
How can anyone argue that an improvement in front brake performance is a bad thing...


Removing proportioning valve moves balance towards the front. All agree?

If balance is right from the start, then it's a bad thing. If balance is too much to the rear from the start, then it's a good thing. All agree?

My view: If you change nothing else (like calipers and disc sizes) then you assume to know things the factory didn't, if you decide to remove the proportioning valve (and thereby change the brake balance). Do you? Probably not.
People that remove the proportioning valve say that they feel the car brakes better, well the front end does, and that can be felt as hard firm braking, the rear wheels contribute less. My first Pantera had had the proportioning valve removed by previous owner, everything else on the brakes looked original. In the rain the front wheels would lock and skid over the pavement and rear wheels didn't really contribute that much. It was terrible.

If on the other hand you upgrade brakes with a vendor kit, you should remove the proportioning valve because their kits are balanced wihout a proportioning valve (I assume Smiler)
I don't even know how it works. How can you change pressure from left to right in the front?
That's BS.

All it is doing is softening the pedal and killing total pressure to the front.

Take the thing out of the system and throw it over the fence at the Chevy guy. It is garbage.

It is not a resale feature on a car.

The stock rear brakes are so weak, no proportioning valve will help balance anything unless you put bigger brakes in the rear.

The rear caliper is a go cart caliper. That's where the thing belongs.
quote:
Originally posted by Cowboy from Hell:

Growing population sounds like a nice way to give more weight to the opinion of a few people.

It appears this "growing population" advocates retention of the proportioning valve based on a theory. A "real" problem caused by its removal was not mentioned, the theory is leaving it in results in better balance. I'd like to rephrase that theory if I may. "The rear brakes are inadequate, so we should reduce the effectiveness of the front brakes so they are more balanced with the rears". But guys ... making the front brakes less powerful means less braking performance! Which is better, two inadequate brakes, or four inadequate brakes?

Removing the proportioning valve measurably shortens the braking distances. That's why owners have been doing it for 40 years. Control while braking is not compromised either. It does not create a two wheel braking situation, the pressure to the rear circuit doesn't change, and the weight on the rear wheels remains the same. The rears are braking just as hard either way. If balanced braking means longer braking distances, then I choose more powerful braking over better balanced braking.

Reducing the power of the front circuit to "balance" the braking front to rear is going about it the wrong way! Wouldn't it be better to increase the power of the rear circuit? I may well agree with Chris that a rear brake upgrade will improve the Pantera's braking performance, but I am not in agreement that removal of the proportioning valve without a rear brake upgrade is a bad idea. I can't go that far Chris.

-G


George,

It's not theory--it's fact.

The stock proportioning valve is actually a pressure-reduction valve. By having different-sized pistons inside, it takes X psi input and delivers Y psi (lower) output.

You advocate taking the thing out with the argument that people have been doing it for a long time. Well, if you look at the back issues of PI and the POCA newsletter from the 1970s and 1980s, you'll see a LOT of (shall we say highly questionable) things that people did a long time ago. Just because it was done a long time ago, doesn't mean it was smart.

With a given amount of pedal pressure, the front and rear brakes will deliver a given amount of stopping performance. If you sabotage the system by removing the proportioning valve (for effectively, that's what it is, unless you've done something else too, such as adding a second rear caliper to each side, which was commonly done at the same time back in the day, and apparently works, from the one example I've driven with that setup), then the front brakes will become more effective with a given amount of pedal pressure. To the (people who only drive their cars gently, and never have to make a panic stop or use the brakes at anywhere near max effectiveness), that sounds like an improvement. But anybody who actually drives his Pantera hard (meaning using the brakes at or close to their design limit) will soon discover that the front brakes are now overly sensitive. Simply put, they will lock prematurely, relative to the rears. Whereas before, it took a healthy amount of pedal pressure to generate wheel lock, now a much lower amount will generate front-wheel lock, with virtually no performance at all coming from the rear brakes. Once the front brakes lock, you've lost all steering control, and you really can't apply any further braking to try to get the rear brakes to stop you, because now you're skidding. Don't forget, a skidding tire increases stopping distances by about 25% over a max-performing braking tire.

Do you even know how the proportioning valve came into being? When the Pantera prototypes were first undergoing testing (which was performed in the USA by a lab in Orange County, by the way--I have a copy of the full report), they suffered from too much front braking, and stopping distances were abysmal. While the proper solution would have been to install better rear calipers, the band-aid fix was to go for a pressure-reduction system for the fronts. Once that was implemented, although pedal pressure was a bit higher, stopping distances were a lot shorter.

And ultimately, that should be the ONLY goal.

I would agree that IF the rear calipers are upgraded and the front ones are left alone, the new system would probably benefit from the removal of the proportioning valve. Only testing would determine the ultimate truth of that however.

I would also agree that anybody who wants to do any really serious driving in a Pantera would be wise to toss the entire braking system over the hedge, and start over with any of the various options provided by the Pantera vendors. As long as the braking SYSTEM is fully engineered, and balanced, and not just a hodge-podge of spiffy-looking components randomly thrown together, then a proportioning valve would be rendered moot and unnecessary altogether.

My Pantera has a complete Wilwood-based system from Dennis Quella, with no proportioning valve, and the braking performance is light-years better than stock. However, that performance isn't really measured on the first stop. On the first stop, a bone-stock Pantera in proper working order (well, one with the pads warmed up) will stop just as well as one equipped with a killer brake system. It's only after repeated stops, where heat starts to come into play, that the aftermarket setups really start to earn their money. They do so via greater rotor mass and venting, which allows the fluid to remain at a reasonable temperature and thus allows the system to continue functioning as it should.

Stock brakes, when exposed to the rigors of track use, will eventually overheat to the point where they become useless until they have cooled off again.

A point worth mentioning is that a stock Pantera in good working order should be able to lock the brakes--lock all four of them if you're determined enough. If yours can't do that, then something is wrong with it. When was the last time you checked the effectiveness of your power brake booster? People seem to completely forget that the Pantera's setup relies on the proper performance of this critical component, and if it is compromised somehow, then braking performance will be measurably reduced (or put another way, braking effort will be measurably increased for a given amount of stopping performance). I suspect that a lot of the people who removed their proportioning valves, did so out of desperation for this very reason.

It's possible to wreck your stock brakes, using your engine.

Huh?

Right--just put a wild camshaft in there that reduces the available vacuum for the power brake booster, and suddenly, your brakes don't work properly anymore. It's easy to then go off on a wild goose chase, trying to fix something that really isn't broken, and condemning the factory engineering when in fact the owner has created the problem himself.

The bottom line is that advocating removal of the stock proportioning valve on a stock brake system that functions as it was when new, is a dangerous thing to do. The brakes should work properly. If they don't, then find out what's wrong with them, and fix it. Don't sacrifice total stopping performance for the sake of expediency and a false sense of security.

(Edit follows)

George, you present a false choice--between having two calipers that work correctly, or four that don't work correctly. Again, I maintain that neither of these is acceptable, and advocating one of these choices is dangerous. I believe that the ONLY acceptable choice is the unstated one, which is four calipers that work properly, as they did when new.

Contrary to your assertion, I'm not attacking any people personally--you included. I'm attacking a dangerous belief that has been held by some, for many years, and has the potential to result in unnecessary damage and/or injury if followed.

To criticize a bad idea is not the same as criticizing the person who espouses it.
It's actually not true that rear braking stays the same when removing the pressure limiting valve from the front circuit, for the simple reason of weight transfer. Sure, the pressure to the rear calipers stays the same but with increased front braking pressure comes increased weight transfer to the front of the car, and a corresponding decrease in traction at the rear. I'm sure removing the valve gives better pedal feel but front to rear balance is ultimately more important when it comes to stopping distances and more importantly, vehicle control while braking.
I am not sure why everyone is arguing about this stuff on this thread. As I read each persons response I am in agreement with them all. Yes, some people get more technical then others about how the system works, ie: weight transfer and the like, yet I believe we are all in agreement.

Balance is the key!!! To remove the stock proportioning valve without an improvement to the rears throws the balance off. The stock system is balanced so to speak with the valve in place.

If the valve is removed, the brake system should have some upgrades to bring it back into balance. Without going into the gnats ass detail on the braking system design, I believe we can sum up this thread by saying that we all agree the key to brake system performance is balance!

Scott
quote:
Contrary to your assertion, I'm not attacking any people personally--you included. I'm attacking a dangerous belief that has been held by some, for many years, and has the potential to result in unnecessary damage and/or injury if followed.


If this unsafe practice has been going on for years where are all the wrecked Panteras from inadequate brake performance due to this modification?

I personally have never heard of one incident. Prove this assertion with documentation and you will have provided the Pantera community with a tremendous service.
quote:
If this unsafe practice has been going on for years where are all the wrecked Panteras from inadequate brake performance due to this modification?

I personally have never heard of one incident. Prove this assertion with documentation and you will have provided the Pantera community with a tremendous service.


party applause
FWIW, I always advocate removing the non-adjustable proportioning valve, for the simple reason that it was designed for Goodyear Arriva belted bias tires or occasionally, Michelin XWX radials, both in rock-hard compounds and tiny contact-patch-sizes compared to what's common on most Panteras 40 years later. And a large number of cars now have bigger rotors, bigger calipers or Porterfield pads with much better frictional qualities than stock. Tires, rotors, pads and even adapting a different master cylinder or brake booster will all vary braking force at the tire/road surface.

Bottom line: if your Pantera has significantly different sized tires from stock, or different calipers or other brake parts, the stock valve is guaranteed to be set wrong, and cannot be adjusted.
As someone said, a sensible test is to remove the valve and try panic-stopping a few times in a deserted parking lot (for safety). If you like the improved braking action with no valve at all, fine- you're done except to get used to the improved stopping power.
But if with the valve gone, you CAN lock up a wheel or two and stability is iffy, an outside observer can tell you which one it was. Then if you wish to go a little further in optimizing your brakes, you can add a manually-adjustable proportioning valve and adjust it for your car with your tires and your brakes. If you later upgrade any of the parts involved, your manual valve can be readjusted to compensate.

One caveat: don't adjust your new valve for a ragged-edge brake balance. Road surfaces vary in friction and if you find yourself on concrete, or damp pavement or dusty blacktop, the friction may be different from your test surface, and again you'll be locking up one or more wheels- often at an inopportune time. Give yourself a little margin for changing conditions.
This has been and continues to be a superb discussion. I missed the 'angry' words, but still completely detect the passion and desire to give sound advice.

Prudence in this vital area (brakes!) means testing with and without the proportioning valve.

Right now, I have a creeping pedal, so the PV is not my initial issue, yet will get its due during the rework.

Chris Bell has been supremely helpful to me, reaching out personally to assist.

Looking forward to more discussion.
I will agree this has become a great discussion on vehicle dynamics, brakes, handling, etc. It really gets you thinking about what a manufacturer has to address to make a great car, especially a high performance sports car that does more than go fast in a straight line.

Below/attached is a comparison where the Pantera GTS was rated number 1...braking from 70 mph was 166ft (Thank you Mike @ The Pantera Place for the chart...hope it's ok to post that without your permission?) Were there caliper/rotor or master cylinder changes as the cars evolved? Did all the Pantera's have the PV in the front brake circuit?

This link shows the best braking cars over the past 40 years. Considering the older tire construction vs some of the numbers on this chart the Pantera GTS was pretty impressive.
http://www.caranddriver.com/fe...hort-stoppers-page-4

I'd be very interested to see how Georges/Mikes Wilwood braked cars compare and one of the Brembo big red calipered cars do compared to the GTS in the chart. The real test for most of these cars would be bringing it down from 150 repeatedly when the caliper and rotor changes really make a difference.

Love this thread...thanks for all the comments. I'm starting to think I may get my checkbook out and go see one of the vendors for a full caliper/rotor/MC kit.

Attachments

Photos (1)
quote:
Originally posted by Tom@Seal Beach:
I will agree this has become a great discussion on vehicle dynamics, brakes, handling, etc. It really gets you thinking about what a manufacturer has to address to make a great car, especially a high performance sports car that does more than go fast in a straight line.

Below/attached is a comparison where the Pantera GTS was rated number 1...braking from 70 mph was 166ft (Thank you Mike @ The Pantera Place for the chart...hope it's ok to post that without your permission?) Were there caliper/rotor or master cylinder changes as the cars evolved? Did all the Pantera's have the PV in the front brake circuit?

This link shows the best braking cars over the past 40 years. Considering the older tire construction vs some of the numbers on this chart the Pantera GTS was pretty impressive.
http://www.caranddriver.com/fe...hort-stoppers-page-4

I'd be very interested to see how Georges/Mikes Wilwood braked cars compare and one of the Brembo big red calipered cars do compared to the GTS in the chart. The real test for most of these cars would be bringing it down from 150 repeatedly when the caliper and rotor changes really make a difference.

Love this thread...thanks for all the comments. I'm starting to think I may get my checkbook out and go see one of the vendors for a full caliper/rotor/MC kit.


Great chart what year was this done. Goes to show that there is more to the pantera than the general unwashed believe. Who said these cars couldn't perform.
quote:
Great chart what year was this done.

Chris it's labeled "1981 PM test"?, but there's no year labeling the cars? It wouldn't surprise me if George, Mike or Boss Wrench know the year and makes of all the cars used in the test, as well as the chassis # and owner of the GTS. LOL you guys are walking dictionaries. That's whats so awesome about these forums...all their knowledge is documented here.
It would be interesting to see this updated.

Although I do remember it I would say that it is a little outdated AND I am skeptical at who is missing from the list.

A couple right off the top of my head are the 911 and the Corvette. Frankly I wouldn't mind seeing the 427 Cobra on there either.

As I recall, the Pantera had a large advantage right out of the gate because of it's price relative to the others really in it's class.

All things equal (who ever said things were equal or the Universe was fair) interesting none the less.
Corvette and 911 for sure...but not so sure a 427 Cobra at 2100-2200 pounds is a fair comparison. Take a gander at the braking distance of the 512 Boxer....almost 40 feet better(20%+ better)than the best. Wonder what calipers and rotors and rubber were on that car.

What's interesting is the Manta on the list is a kit car, tube frame, SBC, fiberglass body, I would have thought it would have done much better due to a weight advantage, but then we don't know what brake parts they used.
quote:
Chris it's labeled "1981 PM test"?, but there's no year labeling the cars? It wouldn't surprise me if George, Mike or Boss Wrench know the year and makes of all the cars used in the test, as well as the chassis # and owner of the GTS. LOL you guys are walking dictionaries. That's whats so awesome about these forums...all their knowledge is documented here.


HAHAHAH!!! This dates from a Popular Mechanics article comparing the then-current sports cars available on the market at the time. All the cars in question were 1981 models (including the Pantera, a late-model GTS imported by PanterAmerica). Unfortunately I don't know anything about that specific car however.

Perhaps surprisingly, at the end of the test, PM rated the Pantera as the best overall sports car you could buy in the USA in 1981 (if my recollection is correct--I read it many years ago). Unfortunately, PM isn't a very credible outfit (despite the apparently extensive and objective testing they conducted), so their pronouncement fell on deaf ears as far as the marketplace was concerned....
Corey’s suggestion to try the brakes both ways and make your own choice is sound advice.

Doug made a point worth repeating, there is no testimony lending credence to the assertion that removal of the proportioning valve is harmful in any way. I certainly would not advocate its removal if there were. Neither do I believe the vendors such as Steve would offer kits for the proportioning valve’s removal if it might create a liability issue for them.

Mike’s story regarding how the proportioning valve came to be is very enlightening, at least for me. It appears the brake system was designed without the proportioning valve, in other words Dallara (or someone else within the DeTomaso organization) designed the brake system with the extremely forward biased brakes intentionally! This also means removal of the proportioning valve is equivalent to removing an alteration orchestrated by Ford engineers and restoring the brake system to the engineered balance Dallara had intended. Now that doesn’t sound so bad does it?

This leads me to a discussion of front to rear brake bias. So settle in guys, pour yourselves a drink, this is going to be one of my long winded posts.

Mike described the front to rear bias of an ideal brake system as being so closely balanced that the front brakes lock-up first, and the rear bakes lock-up shortly thereafter. That is the text book ideal brake bias described by some race car engineering books, but in the real world that is seldom how brake bias is set-up in an amateur race car; and it is universal in the world of street car design that rear brake lock-up is NEVER a good thing; it is something to be avoided. It is desirable for the rear brakes to do as much work as possible, but never so much as to risk the condition of rear brake lock-up. Street cars are by nature heavily front brake biased.

And remember, the Pantera is a GT car, a high performance street car.

When braking there are 3 possible scenarios:

(1) 4 wheel lock-up - It’s fairly easy to understand why 4 wheel lock-up is not a good thing, at that point all 4 tires have lost adhesion to the road and the driver has no control of the vehicle’s speed or its direction of travel. This condition is to be avoided with no exceptions.

(2) Rear wheel lock-up - When the rear wheels lock-up the rear end of a vehicle has a tendency to swing around on the outside, unless the vehicle is traveling in a perfectly straight line. Even when traveling in a straight line the rear end will have a strong tendency to swing in one direction or the other, depending upon centrifugal force, the road surface, tire condition, etc. It can be difficult to avoid rear wheel lock-up under all conditions because of the wide range of variables affecting weight transfer, centrifugal force and the chassis’ ability to cope with them. The variables include the driver’s driving style, road conditions, varying corner speeds, shock absorber wear, tire wear, tire pressure, changes in tire make and model, varying outdoor temperatures, and varying vehicle load (passengers, fuel level, luggage, etc.). Once the rear end starts swinging it is nearly impossible to stop; this tendency is even stronger with a mid-engine vehicle … which no doubt contributed to Dallara’s decision to set up the brake bias the way he did.

(3) Front wheel lock-up – If a vehicle is traveling in a straight line when the front wheels lock-up, the vehicle tends to continue to travel in a straight line. If the vehicle is cornering when the front wheels lock-up the vehicle will begin to travel forward in a straight path towards the outside of the corner. Unlike rear wheel lock-up, front wheel lock-up is fairly easy to recover from, all the driver needs to do is lighten the force on the brake pedal, allowing the front tires to regain adhesion, and the vehicle will resume cornering. A driver becomes aware of the loss of front tire adhesion quickly because they feel the loss of directional control via the steering wheel in less than a second’s time. If they are driving an open wheel race car they can see the tire smoke from the skidding tires almost as quickly as they feel the loss of directional control. Front wheel lock-up is considered by far the best of the 3 scenarios.

Both passenger cars and race cars are set up with a bias towards the front brakes, not just because most of a vehicle’s weight transfers to the front wheels under braking, but also because it is preferable for the front tires to lose adhesion first. And although it is important for the rear brakes to shoulder as much of the braking chore as possible, vehicle dynamics make it equally important to have a margin of error built into the brake bias to avoid rear wheel lock-up under dynamic or varying conditions. In the top levels of racing the extra front bias for that margin of error is often very small, the brakes are set up as Mike described, the front brakes will lock up just before the rears under heavy straight line braking. In amateur racing the norm is more forward bias; and street cars are another thing altogether because the range of variables encountered by a street car are tenfold greater than the variables encountered by a racing car.

Fixed – linear – mechanical brake bias is “built-in” to vehicle brake systems in many ways. The size of brake disks can be varied front to back, the size of brake pads can be varied front to back, the size or number of caliper pistons can be varied front to back, and dual master cylinders can be employed having different sized pistons for front and rear circuits.

Besides these fixed means for providing front to rear brake bias, race cars usually have a means for varying the brake bias as well; this usually entails a bias bar between the dual master cylinders. This allows racers to compensate for temperatures, tracks, or tires. On top of that, some types of racing make it necessary for the driver to be capable of adjusting brake bias during the race. This allows the driver to compensate for changing weather, tire wear, changing track conditions and even varying fuel levels. In that application a cockpit mounted knob or lever attached to a cable assembly that manipulates the bias bar is often employed. I’d like to point out however, while the professional drivers use those cockpit mounted brake bias adjusting gadgets, the amateurs usually leave them alone.

With all these mechanical means to provide fixed – linear brake bias, you may be wondering why a hydraulic “proportioning valve” is needed at all. At least that’s what I’m hoping you’re wondering because that’s what I want to describe next.

A proportioning valve is not a device for setting linear brake bias; it does not proportion brake force front to rear in a linear sense, the proportioning valve we are most familiar with is a hydraulic pressure limiter. Observe the graph below.



The hydraulic pressure input equals the hydraulic pressure output until the “knee point” setting is reached, from that point onward the output changes very little. In the average car with a proportioning valve attached to the rear brake circuit this means under light braking, when there is no chance of the rear wheels locking-up, the rear brakes are allowed to receive full brake pressure and contribute significantly to slowing or stopping the vehicle. But under heavy braking the pressure to the rear wheels is severely limited and the braking bias shifts drastically to the front tires. This should indicate just how badly the major auto designers wish to avoid rear wheel lock-up, and is probably the other consideration explaining why Dallara designed the brake system with the extreme front mechanical bias it has.

I also hope this explains why anyone considering installation of an aftermarket “adjustable” proportioning valve in the Pantera’s front brake circuit shouldn’t do so. You do not want a device with a “knee point” limiting FRONT brake pressure in this way. Proportioning valves are designed strictly for rear brake circuits.

DeTomaso describes the valve I call the “proportioning valve” as a “front brake pressure control valve”. Mike described it thusly:

quote:
Originally posted by Mike Drew:

The stock proportioning valve is actually a pressure-reduction valve. By having different-sized pistons inside, it takes X psi input and delivers Y psi (lower) output.



In other words, it reduces hydraulic pressure in a linear fashion; it does not function like a classic proportioning valve. I have heard this description before, I have never verified if this is accurate, but I am willing to accept it as truth for arguments sake.

Am I getting too techy for anyone, or are you guys still hanging with me? Have another drink. I’ve had several myself.

A question for Mike, has anybody truly verified the Pantera’s proportioning valve truly does not have a knee point built into it, that it is strictly a linear bias device, or is this just an assumption?

I do not agree with painting a description of the Pantera brake system with the “proportioning valve” installed as finely balanced, and removing the valve as throwing the brakes way off balance. As explained above, even with the valve in place the brakes must still have a significant margin for error built into the front to rear brake bias, to compensate for all the possible variables encountered by a street car. If the oem brake system were truly "finely balanced" then changing tire sizes or even using tires with different rubber compounds would be enough to throw-off the front to rear bias.

If the front disks had been ventilated I doubt if the proportioning valve would have ever been installed. I’m supposing that brake fade under repeated hard braking was the concern at Ford. For that reason I am willing to concede that the addition of ventilated front disks should accompany the recommendation to remove the “proportioning valve”. I’m guilty of not emphasizing that enough.

I’ve also been meaning to mention Chris’ rear brake upgrade kit, so now is as good a time as ever, I think Chris’ new kit should be added to the list of essential Pantera upgrades. I’m not aware of any other brake upgrade that involves just the rear brakes upgraded to complement the braking capabilities of the oem front brakes (sans the damn proportioning valve). Good stuff Chris.

So Adams lets amend my “essentials” list for the brakes to include Chris’ rear brake kit. I wasn’t aware of its existence until he mentioned it earlier in this thread. I know Chris and can vouch for him, he’s good people … even though he installed a Chevy motor in his white Pantera. We all make mistakes. Razzer

Ideally the Pantera’s front disks should have been ventilated. The Pantera was the most expensive car sitting on the Lincoln dealer’s lot, and it didn’t even have ventilated disks, a feature even the lowly Mustang had. If you want to know which company was responsible for the solid front disks, I'd like to point out to you the European GTS had ventillated front disks. The solid disks were a Ford spec.

If more rear brake bias than that provided by Dallara was desired Ford should have accomplished this mechanically with stronger rear brakes, not hydraulically by lowering the pressure to the front brakes. That’s just flippin’ crazy.


_________________________________________________________________________

The 1981 Popular Mechanics exotic car comparison test (March 1981) didn’t paint the Pantera in as good a light as it could have. Phil Hill wrote some complimentary things about the Pantera, but he also commented even though the Pantera had the most points, he didn’t feel safe driving it. You know the old saying, one Oh S#!t cancels a hundred atta boys. And the editors of Popular Mechanics stated even though the Pantera won the test, the Porsche 928 was the car they would most like to own. Good grief! In my opinion, Pantera bashing was as strong as ever in that article. Can you think of any other auto comparison test where the winning vehicle was so under-played? If the guys importing the Pantera in 1981 (Panteramerica) had purchased some advertising the negative comments would have probably been omitted. As it stands the magazine article is a mixed bag of good and bad.

Popular Mechanics March 1981, page 112

-G
Ask 10 people, get 10 opinions. The weight of the test, the cost of the Pantera in relationship to the others was a large factor in it winning.

I'm not familiar with The last Panteras but are their brakes the same as the original US Ford imports?

Incidentally, I won't necessarily value Hill's opinion as the ultimate. He has shown me on more then one occasion that he always has an ax to grind.

To my memory, he always had a high regard for the F cars?

As far as front to rear bias in the design vs. the production, don't forget that the Pantera is and involvement of a car from the Mangusta.

Anyone who follwed the development of the Mangusta should note that when first tested by the auto press the car was close to a nightmare to drive because of it's trailing throttle oversteer.

A term incidentally that was coined because of the Mangusta.

It is also a big reason why Ford backed out of the original verbal agreement to DT about importing it and the reason DT called it the Mangusta.

The Pantera design all but eliminated the oversteer but part of that evolution away from the 'goose problems was the braking system.

If you look at the Pantera brakes the rear caliper and pad is so small in regards to the front that it is impossible to make the rears lock up first, with or without the stock proportioning valve.

That valve is merly extra insurance as far as the Ford engineering involvement was concerned, in my opinion.

Granted the brakes aren't normally going to make a car oversteer, snap oversteer as it were, but the slightest tendency in a turn for the rear to lock up COULD in the mind of some, launch this thing into the weeds like a tornado spinning.
Paranoia would likely prevail to all legally responsible for unleashing a lethal weapon upon the public considering the liability lawyers like Ralph Nadar sitting waiting for the next sacrificial lamb.

Ford simply wanted no more of the "Unsafe at any speed" press.

Maybe consider it an early mechanical ABS design?

No one to this day has produced an iota of documentation even suggesting the removal of the valve is a negative.
quote:
So Adams lets amend my “essentials” list for the brakes to include Chris’ rear brake kit. I wasn’t aware of its existence until he mentioned it earlier in this thread. I know Chris and can vouch for him, he’s good people … even though he installed a Chevy motor in his white Pantera. We all make mistakes. Razzer


Very nice write up George! And thanks for the laugh! (on the Chevy comment) roll on floor
quote:
Originally posted by Cowboy from Hell:
Corey’s suggestion to try the brakes both ways and make your own choice is sound advice.

Doug made a point worth repeating, there is no testimony lending credence to the assertion that removal of the proportioning valve is harmful in any way. I certainly would not advocate its removal if there were. Neither do I believe the vendors such as Steve would offer kits for the proportioning valve’s removal if it might create a liability issue for them.


The vendors don't seem to be overly concerned about liability. All of them are selling brake systems that are clearly labeled by the manufacturer as "for racing use only"; at least one of them removes all those warning inserts from the packaging before sending it on to the customers. Although as a grown-up I don't feel there is any great inherent danger in using 'racing' brakes on the street, a sharp attorney looking for some deep-pockets cash after an accident might not feel the same. The vendors manage to sleep at night (presumably) so they must not think the liability risk is great enough to warrant not offering these systems to the public for street use.

quote:
Mike’s story regarding how the proportioning valve came to be is very enlightening, at least for me. It appears the brake system was designed without the proportioning valve, in other words Dallara (or someone else within the DeTomaso organization) designed the brake system with the extremely forward biased brakes intentionally! This also means removal of the proportioning valve is equivalent to removing an alteration orchestrated by Ford engineers and restoring the brake system to the engineered balance Dallara had intended. Now that doesn’t sound so bad does it?


Sorry George, that particular argument doesn't hold any water, particularly when viewed in the context of the Mangusta, whose brake bias was a complete disaster. Those things had so much front brake bias that the rears were nothing more than ballast. Some of the cars had a proportioning valve from the factory, while others didn't. That valve was located at the bottom of the firewall on the engine-bay side; I confess I don't know if reduced pressure to the front or the rear. But clearly their engineering department left a lot to be desired in that regard.

That's why Ford had to re-engineer the Pantera system slightly, when the prototype cars failed to meet DOT standards for braking performance. The fix was a very expedient one, when a proper fix would have been a complete re-engineering of the system with bigger/better rear calipers.

quote:
This leads me to a discussion of front to rear brake bias. So settle in guys, pour yourselves a drink, this is going to be one of my long winded posts.

Mike described the front to rear bias of an ideal brake system as being so closely balanced that the front brakes lock-up first, and the rear bakes lock-up shortly thereafter.


If I said 'shortly thereafter' I misspoke. They should lock up some time later, but not immediately afterwards. But they should lock up eventually.

quote:
That is the text book ideal brake bias described by some race car engineering books, but in the real world that is seldom how brake bias is set-up in an amateur race car; and it is universal in the world of street car design that rear brake lock-up is NEVER a good thing; it is something to be avoided. It is desirable for the rear brakes to do as much work as possible, but never so much as to risk the condition of rear brake lock-up. Street cars are by nature heavily front brake biased.


Very true!

quote:
And remember, the Pantera is a GT car, a high performance street car.

When braking there are 3 possible scenarios:

(1) 4 wheel lock-up - It’s fairly easy to understand why 4 wheel lock-up is not a good thing, at that point all 4 tires have lost adhesion to the road and the driver has no control of the vehicle’s speed or its direction of travel. This condition is to be avoided with no exceptions.

(2) Rear wheel lock-up - When the rear wheels lock-up the rear end of a vehicle has a tendency to swing around on the outside, unless the vehicle is traveling in a perfectly straight line. Even when traveling in a straight line the rear end will have a strong tendency to swing in one direction or the other, depending upon centrifugal force, the road surface, tire condition, etc. It can be difficult to avoid rear wheel lock-up under all conditions because of the wide range of variables affecting weight transfer, centrifugal force and the chassis’ ability to cope with them. The variables include the driver’s driving style, road conditions, varying corner speeds, shock absorber wear, tire wear, tire pressure, changes in tire make and model, varying outdoor temperatures, and varying vehicle load (passengers, fuel level, luggage, etc.). Once the rear end starts swinging it is nearly impossible to stop; this tendency is even stronger with a mid-engine vehicle … which no doubt contributed to Dallara’s decision to set up the brake bias the way he did.

(3) Front wheel lock-up – If a vehicle is traveling in a straight line when the front wheels lock-up, the vehicle tends to continue to travel in a straight line. If the vehicle is cornering when the front wheels lock-up the vehicle will begin to travel forward in a straight path towards the outside of the corner. Unlike rear wheel lock-up, front wheel lock-up is fairly easy to recover from, all the driver needs to do is lighten the force on the brake pedal, allowing the front tires to regain adhesion, and the vehicle will resume cornering. A driver becomes aware of the loss of front tire adhesion quickly because they feel the loss of directional control via the steering wheel in less than a second’s time. If they are driving an open wheel race car they can see the tire smoke from the skidding tires almost as quickly as they feel the loss of directional control. Front wheel lock-up is considered by far the best of the 3 scenarios.


Agreed, with a strong caveat. Four-wheel lockup would only result from driver error (braking too hard). A proper braking system should have the capability of achieving it, and be engineered so that the driver can control his braking to approach it, but not go over the edge. Prior to the advent of ABS, virtually every car sold in semi-modern times could easily do so--including the Pantera.

I don't know of any non-ABS car that was ever designed to intentionally prevent the brakes from fully working in that regard?


quote:
Both passenger cars and race cars are set up with a bias towards the front brakes, not just because most of a vehicle’s weight transfers to the front wheels under braking, but also because it is preferable for the front tires to lose adhesion first. And although it is important for the rear brakes to shoulder as much of the braking chore as possible, vehicle dynamics make it equally important to have a margin of error built into the brake bias to avoid rear wheel lock-up under dynamic or varying conditions. In the top levels of racing the extra front bias for that margin of error is often very small, the brakes are set up as Mike described, the front brakes will lock up just before the rears under heavy straight line braking. In amateur racing the norm is more forward bias; and street cars are another thing altogether because the range of variables encountered by a street car are tenfold greater than the variables encountered by a racing car.


Very much agreed!

quote:
Fixed – linear – mechanical brake bias is “built-in” to vehicle brake systems in many ways. The size of brake disks can be varied front to back, the size of brake pads can be varied front to back, the size or number of caliper pistons can be varied front to back, and dual master cylinders can be employed having different sized pistons for front and rear circuits.

Besides these fixed means for providing front to rear brake bias, race cars usually have a means for varying the brake bias as well; this usually entails a bias bar between the dual master cylinders. This allows racers to compensate for temperatures, tracks, or tires. On top of that, some types of racing make it necessary for the driver to be capable of adjusting brake bias during the race. This allows the driver to compensate for changing weather, tire wear, changing track conditions and even varying fuel levels. In that application a cockpit mounted knob or lever attached to a cable assembly that manipulates the bias bar is often employed. I’d like to point out however, while the professional drivers use those cockpit mounted brake bias adjusting gadgets, the amateurs usually leave them alone.

With all these mechanical means to provide fixed – linear brake bias, you may be wondering why a hydraulic “proportioning valve” is needed at all. At least that’s what I’m hoping you’re wondering because that’s what I want to describe next.

A proportioning valve is not a device for setting linear brake bias; it does not proportion brake force front to rear in a linear sense, the proportioning valve we are most familiar with is a hydraulic pressure limiter. Observe the graph below.



The hydraulic pressure input equals the hydraulic pressure output until the “knee point” setting is reached, from that point onward the output changes very little. In the average car with a proportioning valve attached to the rear brake circuit this means under light braking, when there is no chance of the rear wheels locking-up, the rear brakes are allowed to receive full brake pressure and contribute significantly to slowing or stopping the vehicle. But under heavy braking the pressure to the rear wheels is severely limited and the braking bias shifts drastically to the front tires. This should indicate just how badly the major auto designers wish to avoid rear wheel lock-up, and is probably the other consideration explaining why Dallara designed the brake system with the extreme front mechanical bias it has.


That last part is a pretty long reach, but you raise an EXCELLENT point about the characteristics of adjustable prop valves, one that I only recently learned myself. I presumed (and their literature often seems to indicate) that they reduce pressure in a linear fashion, but the non-linear reduction you describe above makes a lot of sense when they are employed in the rear circuit. It also makes them sub-optimal when employed in the front circuit. Because the harder you brake (with one of those valves in the front circuit), the more the bias shifts towards the rear, exactly what you don't want. So if you have one of these, you have to have it adjusted rather conservatively. As you said above, you never, EVER want the rear wheels to lock first.

With an adjustable valve set up to ABSOLUTELY ensure that the rear brakes don't lock up first, it will deliver less-than-optimal pressure to the rear brakes, most of the time. However, it will still deliver substantially MORE pressure to the rear brakes, than not running a valve at all. So while it's sub-optimal, it's still demonstrably better.

quote:
I also hope this explains why anyone considering installation of an aftermarket “adjustable” proportioning valve in the Pantera’s front brake circuit shouldn’t do so. You do not want a device with a “knee point” limiting FRONT brake pressure in this way. Proportioning valves are designed strictly for rear brake circuits.

DeTomaso describes the valve I call the “proportioning valve” as a “front brake pressure control valve”. Mike described it thusly:

quote:
Originally posted by Mike Drew:

The stock proportioning valve is actually a pressure-reduction valve. By having different-sized pistons inside, it takes X psi input and delivers Y psi (lower) output.



In other words, it reduces hydraulic pressure in a linear fashion; it does not function like a classic proportioning valve. I have heard this description before, I have never verified if this is accurate, but I am willing to accept it as truth for arguments sake.


It's true, and has been demonstrated as such by Bill Taylor (see below)

quote:
Am I getting too techy for anyone, or are you guys still hanging with me? Have another drink. I’ve had several myself.


HAHAHA!!! This is a great discussion! Smiler

quote:
A question for Mike, has anybody truly verified the Pantera’s proportioning valve truly does not have a knee point built into it, that it is strictly a linear bias device, or is this just an assumption?


Good question! It is a linear pressure reduction device. Bill Taylor built a test rig and measured input/output of a stock valve; here is his graph:



While the output line is not perfectly aligned with the input line, it is close enough to linear to be considered as such. It's a pure pressure reduction valve. A full accounting of his test protocol, and photos of a disassembled valve, appear on Mike Dailey’s Panteraplace website, here:

Pantera Place--Brake proportioning valve

quote:
I do not agree with painting a description of the Pantera brake system with the “proportioning valve” installed as finely balanced, and removing the valve as throwing the brakes way off balance. As explained above, even with the valve in place the brakes must still have a significant margin for error built into the front to rear brake bias, to compensate for all the possible variables encountered by a street car. If the oem brake system were truly "finely balanced" then changing tire sizes or even using tires with different rubber compounds would be enough to throw-off the front to rear bias.


Which it does! Most people have upgraded their Panteras to use wider tires, and the rear tires are normally relatively much wider than the fronts (that is, the increase in rear size is much greater than the increase in front size). This means that the rear could potentially use even more brake bias than before, which would mean (if the stock calipers were maintained) that the front brake pressure would need to be reduced even further than the stock scheme, in order to maintain appropriate front/rear bias and allow the rear brakes to work properly.

quote:
If the front disks had been ventilated I doubt if the proportioning valve would have ever been installed. I’m supposing that brake fade under repeated hard braking was the concern at Ford. For that reason I am willing to concede that the addition of ventilated front disks should accompany the recommendation to remove the “proportioning valve”. I’m guilty of not emphasizing that enough.


Those are unrelated arguments. A vented disc will stop just as well an an unvented disc, when at normal operating temperature. A vented disc will allow temperatures to be maintained in the useable range, and allow the brakes to continue working when they have been used aggressively. Under normal driving conditions, brakes never get hot enough to suffer heat-induced brake fade, so vented rotors would have no effect on braking bias. If the brakes are biased properly and are used aggressively, all four will heat up, so all four would benefit from venting. Putting vented rotors in the front and solid rotors in the back would probably result in the brake bias slowly shifting forward as the rear brakes overheated and the front ones didn't, under aggressive driving conditions. That's not really optimal either.

quote:
I’ve also been meaning to mention Chris’ rear brake upgrade kit, so now is as good a time as ever, I think Chris’ new kit should be added to the list of essential Pantera upgrades. I’m not aware of any other brake upgrade that involves just the rear brakes upgraded to complement the braking capabilities of the oem front brakes (sans the damn proportioning valve). Good stuff Chris.


It sounds like Chris has found and filled a niche that has been overlooked for far too long. However, I can't find anything specific about it anywhere. Chris, would you mind (and George, would you please allow) generating a bit of an advertisement for them here, and let everyone know exactly what George is referring to? I think for somebody trying to improve their braking on a budget, an improved rear caliper setup that would deliver proper braking without pressure reduction anywhere in the system would be absolutely the best thing ever!

quote:
So Adams lets amend my “essentials” list for the brakes to include Chris’ rear brake kit. I wasn’t aware of its existence until he mentioned it earlier in this thread. I know Chris and can vouch for him, he’s good people … even though he installed a Chevy motor in his white Pantera. We all make mistakes. Razzer


HAHAHAH!!!

quote:
Ideally the Pantera’s front disks should have been ventilated.


No--ideally all FOUR of the Pantera's discs should have been ventilated!

quote:
The Pantera was the most expensive car sitting on the Lincoln dealer’s lot, and it didn’t even have ventilated disks, a feature even the lowly Mustang had. If you want to know which company was responsible for the solid front disks, I'd like to point out to you the European GTS had ventilated front disks. The solid disks were a Ford spec.


Vented discs were one of many OPTIONS on the Euro GTS, but did not come standard, nor did the 10-inch wheels, etc. I've worked on several different Euro GTS Panteras, both here and in Europe, and the vast majority came with solid rotors from the factory.

quote:
If more rear brake bias than that provided by Dallara was desired Ford should have accomplished this mechanically with stronger rear brakes, not hydraulically by lowering the pressure to the front brakes. That’s just flippin’ crazy.



Although we're not supposed to insult people here, I am going to go out on a limb and say that it wasn't just crazy, it was just plain STUPID. Ford and De Tomaso were under both time and cost constraints to bring the car to market, and the band-aid fix took minutes to implement while sourcing all new rear brakes and redesigning the system would have taken weeks or months. The cars have suffered ever since due to this shortsightedness (as well as similar shortcuts on numerous other systems, i.e. air conditioning).

In answer to other’s questions, yes, the standard Panteras through the end of production all came with the 1971-spec brake system. Better brakes were an option on the narrow-body cars, but seemingly not many received them. The GT5 and GT5-S came standard with vastly upgraded brakes. (And yet, curiously, I believe that they still retained the brake bias valve??? Can somebody who owns one of those factory widebody cars confirm that?)

And Doug, as to your statement that nobody has ever demonstrated that Panteras have been wrecked as a result of degrading the rear brake effectiveness, that's a rather specious argument. We all know that Panteras have been crashed over the years; some of them had received this modification. It would be next to impossible to 'prove' that an accident occurred because of this modification, and would have been avoided without it.

In discussing the argument in favor of degrading the rear brakes, I'm reminded that there are people who still, today, stridently believe that you're safer NOT wearing seat belts. That was a long-held belief for years when seat belts first came out, and there was plenty of anecdotal evidence available to support such contentions (heck, even I can provide one; many years ago a guy in Nor-Cal drove his Pantera straight into a telephone-pole-sized tree, hitting so hard that the trunk ended up touching the wiper grilles! The front was bent into a V and the headlights were only a couple of feet apart. He wasn't wearing his seat belt and was unhurt--except for injuries to his arm afterwards, when he deliberately broke the window to get out of the car).

While that mindset was prevalent back in the day, with the passage of time, more and more people have come to realize that seat belts are a good thing. Similarly, while many years ago people (including some Pantera vendors) advocated increasing front caliper performance at the expense of total vehicle balance, that idea is no longer as widely held as it once was.

As to the braking issue, while it's impossible to demonstrate that an accident could be caused by partially disabling the rear brakes, intuitively one can see that it could be true. What COULD be demonstrated empirically is that stopping distances under max-effort braking will increase if the valve is removed, or conversely, will be reduced if it is installed. Ford proved that conclusively back in 1971.

But, as many people have mentioned, times have changed, we're all running different tires, etc. etc. so the specifics of those tests are no longer perfectly valid for any of us. What is needed is a new round of objective, empirical testing. And I've been keen to do just that.

My fiancee's Pantera #1765 had stock brakes, with a blown-out master cylinder, and a badly leaking stock pressure reduction valve. The folks in PCNC got together and installed a new Wilwood master from Dennis Quella, and an adjustable (knee-style) Wilwood proportioning valve in the front system. (She has Pantera East 16/17 inch Campagnolo clones on her car with 245/45-16 and 335/35-17 Dunlop tires). The valve has been left in the full-open position (no pressure reduction) so that it effectively mimics having no valve at all.

It does not stop well.

She drove it at a few track days, and totally destroyed her front brake pads due to the excessive front bias. New Porterfield pads have just been installed in front, and new rear Porterfields will be going in shortly, along with braided stainless steel flex hoses.

Once that is complete, her car will represent a sizeable percentage of the demographic here—stock calipers, upgraded pads, braided stainless hoses, aftermarket master cylinder, and oversize wheels/tires. We will then undertake a scientific test regimen to establish the optimal positioning for the valve. There is an industrial park near my house that is largely uncompleted, offering a straight, wide road about a half-mile long with zero traffic. We will use both distance- and temperature-measuring equipment, to try to get some empirical data to support or disprove the contentions that one can only otherwise intuit.

We’ll get the brakes heated up by driving around and performing a few hard stops. Then we’ll do a max-effort stop from 50 mph and measure the stopping distance, and front and rear rotor temps. Then we’ll start dialing in some rearward bias by reducing the pressure to the front system, and repeat. By measuring front rotor temp, we’ll ensure that our data isn’t being skewed by thermal runaway (the brakes getting hotter and hotter on each stop). We’ll figure out how much cooling is necessary between tests so that front rotor temps remain fairly constant, and rear temps increase as braking increases. We’ll continue numerous times until we have gone too far (if in fact it’s even possible to do so) and the rear end locks up. Then we will back well away from that.

I am expecting that some brake restriction to the front system will result in shorter stopping distances than no restriction. It remains to be seen what will happen first after that—rear brake lockup, or front brake ineffectiveness due to excessive restriction. If stopping distances initially decrease, and then start increasing, with front rotor temps dropping and pedal effort increasing, then that will probably demonstrate the point where the adjustable valve hurts more than it helps.

Eventually we’ll hopefully arrive at an optimal, safe setting that affords the best possible braking with the constraints that the stock braking hardware produces.

And then, she’ll want to buy a complete aftermarket braking system!
Any manufacturer or vendor selling Pantera or 351 Cleveland specific parts is always welcome to advertise (announce) the availability and specific details regarding those parts in the community announcement forum. I think Chris is aware of this. If not, he is now.
_________________________

Reading Bill Taylor's graph regarding his proportioning valve test results, I disagree with your assessment. The Pantera "proportioning valve" does indeed have a knee in the curve, at 650 psi. Below 650 psi the input equals the output, it is linear; above 650 psi the pressure is reduced by about 33%. It would be much more obvious if the horizontal scale were expanded.
_________________________

Sure ventillated rear disks are preferred, optimal, to be recommended. I would want them for my Pantera if it didn't already have them. But ... I've seen many US manufactured cars get away with solid rear disks, ventillated only in the front. This is why I've repeatedly mentioned only ventillated front rotors. The fronts are more essential, and my comments to Adams were originally the bare necessities.

Some people don't want to spend any more money than necessary, others want to keep their cars as original as possible, changing only the essentials. My comments have been geared for such owners.

But its a moot point now, because in the future my advice regarding Pantera brakes shall be:

(1) Ventillated front rotors
(2) EBC, Porterfield or Raybestos front pads
(3) SACC Restorations rear brake kit
(4) Remove the proportioning valve and mail it to Mike Drew, he loves them Razzer

I feel accurate calling it a proportioning valve now!

-G
Further to my earlier post about the testing that was performed in the USA and the requirement for brake proportioning, I dug up the report to remind myself what it said, and see that I misremembered it.

Two cars were used for testing, #1006 and #1011. #1006 was tested first, in late August/early September 1970, and the tests were conducted at Riverside Raceway, with ambient temps in the 90s. Following the successful conclusion of the tests, they went to repeat them on #1011 but found excessive pedal effort was required. They suspended the tests, and according to the documents, eventually they swapped the master cylinder *and the proportioning valve* over from #1006 to #1011. That restored normal braking operation, and the tests continued with #1011, which more-or-less mirrored the results earlier attained with #1006. The tests on the now-functional #1011 took place in mid-September 1970.

So, clearly the cars had the proportioning valve from the start. Where earlier I said that I'd read that it had to be added to the car to make it stop properly, now I see that it had to be transferred from one car to the other; presumably the second car had one installed originally and it was just replaced, not added. So therefore, for better or for worse, it was part of the original design.

It's really interesting to see how aggressive and comprehensive the brake tests were, and how well the car performed. It's also interesting to note that at the extreme limit, on one test one of the cars experienced lockup of the left REAR wheel. That shows that bias was fairly evenly distributed between the front and rear, when the cars were new and the tires were skinny.

It was interesting to see that they were not trying to achieve (nor did they measure) stopping distance; rather they sought to achieve a fixed deceleration rate, measured in feet per second per second. They measured pedal effort to achieve that rate on multiple stops, to measure brake fade--if it took more pressure to achieve a given rate of deceleration, then that indicated that the brakes were fading. They also did post-fade testing, to make sure the brakes recovered once they had cooled, and they did water testing--driving the car through 9 inches of standing water to soak the system, then honking on the brakes etc.

Rotor temperatures were measured, and as expected with solid rotors, they got quite hot--up to 600 degrees after 15 consecutive 60-0 stops with no cooling in between. However, brake pedal effort to achieve the desired fixed deceleration rate actually remained about the same (the effort went down as the brakes heated up, then went back up as they heated up further, so that the effort required on the last stop was about the same as that required on the first stop).

Although they didn't report the actual stopping distance, if you're starting from a fixed speed and slowing at a fixed rate, time and again, the stopping distance must be the same (plus or minus a bit). So the car passed the brake fade and recovery tests with flying colors.

They also tested braking with each system (front and rear) disconnected; there they did measure braking distance. The government requirement was a stop from 60 mph in 646 feet; with the front disconnected it took 378 feet, rear disconnected it was 284.6 feet.

They also checked for performance with the power assist disconnected, from 60 mph; the requirement was a stop in 600 feet, and the two cars did it in 319.5 and 324.2 feet respectively.

The report on the braking system tests (oh yeah, I forgot to mention they also tested the effectiveness of the emergency brake) is over 100 pages long.

The bottom line is that when the car was new, it had GREAT brakes relative to your average 1971 car, and their performance would certainly be more than acceptable by today's standards (for normal street use). If a stock Pantera today doesn't have great brakes for street driving, something is WRONG and needs to be fixed.

That said, they certainly can be improved upon, and there is never any harm in doing so!
Taking the argument that it's a good thing to increase front brake effect at the expense of rear brakes (and ruining the balance) to the extreme, why not just dismantle and plug three brake lines? The remaining wheel will get plenty of fluid pressure, and the car would stop on a dime. Not!

Eeker

On a more serious note, we seem to forget one thing. The car was originally engineered to have too much brake force at the front and too little at the back, to avoid customers locking the rears. If you remove the proportioning valve, you don't remedy that, on the contrary, you push even more of the braking power to the front. Now even your wife can drive it on ice...

Anybody with an original setup should either do the whole thing, or get better calipers for the rear. If those calipers are good enough to significantly increase rear brake force, then it might make sense to remove the (dare I say it?) proportioning valve.

This winter I'm removing all my orig brakes and installing kit from Dennis Quella. My expectations are high...
Mike your comments on the testing done by the factory is quite interesting....I must surmise that "The government requirement was a stop from 60 mph in 646 feet" (OMG thats over two football fields!) proves that Fred Flintsone's braking system of dragging his feet was also adequate, or for that matter who needs brakes at all, just turn the motor off and downshift (too much rear bias), the car will stop eventually and the higher compression motors will be even more effective. No wonder some US car designs fell so far behind the rest of the world in the 70's and 80's!

As I read about all these test being done, I remembered...when I was in high school in the early to mid 70's there was a Lincoln Mercury dealer (I think Fladboe Lincoln Mercury) in Long Beach that my friends and I would stop at and marvel at the new Pantera's. Somehow we started talking with one of the mechanics who wrenched on the Pantera's (we thought this guy was GOD)and he turned us on to all the brake parts (calipers and rotors, front and rear) that the dealer pulled off the Pantera's that were supposedly faulty and under warranty. He said some were bad and they toss them in the trash, but that most were still good parts, but it was the dealers policy to make sure the Pantera's had only the best parts on them and to make sure that Pantera owners were very happy with the cars. I retrieved all the parts from this mechanics bin from only that week and ended up 1-2 set of front calipers and rotors and 3-4 full sets of rear brakes. I guess there were some issues they found on the rears due to the number of parts he had. I thought some how I would find enough good parts out of the mess to put on my 67 Fast Back Mustang GT figuring that the parts off a Pantera had to be way better than what the Mustang had. Back then we had a lot of fun going to junk yards searching for muscle car engines and different parts, so the brakes off a Pantera were a real find. Well I never got around to putting the brakes on the Mustang and finally my Dad (sit down and place your head in your hands!)just chucked all the parts in the TRASH after 15 or 20 years of sitting in his garage.
quote:
(3) SACC Restorations rear brake kit


Thank you for recommending our kit George!

Our rear upgrade kit information can be seen at our blog here: http://blog.saccrestorations.n...r-brake-upgrade-kit/

We haven't put it up for sale yet on the website as we are still testing, but you will be able to order it in the next few days.

This kit will include two, 4 piston Wilwood calipers that are a direct bolt on replacement, two red powder coated mounting brackets, all mounting hardware, and PolyMatrix Brake Pads.

All of our brackets are designed in CAD.

With this upgrade, you can still use the stock master cylinder.

quote:
If those calipers are good enough to significantly increase rear brake force, then it might make sense to remove the (dare I say it?) proportioning valve.


This kit does indeed call for removing the proportioning valve as with it out, the brakes are very balanced.

This will be on sale for $499.95 for the next month (regularly $599.95).

Thanks,
Chris


The kit looks like choice quality stuff, something this hobby has needed for a long time. combining that rear brake kit with vented front rotors & removal of the proportioning valve is a great fix for the oem brakes. I hope a lot of owners will jump on this. It will even work with the oem 15" Campy wheels.

Way to go Chris. Are the rears biased about where I think they are?

-G
Thank you very much George! We hope we can get our kit out their and improve upon the brakes on many Panteras..

The balance, or bias, will definitely depend on the specific installation such as tire size. It is designed and tested though to have the bias more towards the front. If on a specific installation the bias is towards the rears, a proportioning valve in the rear circuit will be needed.

For most people though, it should be balanced out of the box...
quote:
Originally posted by PanteraDoug:
I like the kit but would like an option for the rotor too?


What size rotors would you like? And do you want calipers and rotors for all four wheels? We can customize it anyway you want..
Chris since this keeps the existing master and booster in place what tire sizes has this been tested on? I'm running 245/40-17 and 285/40-18's. My guess is I'm smaller in the rear than you're running on that Z06 contraption (yeah I know it has more HP and Torque)LOL couldn't resist taking a poke. Would I need to run a proportioning valve on the rear circuit with less rubber on the ground with your rear calipers? And what pads would work well with this combination? Now comes the fine tuning...I remember Porterfield puts out harder and softer pads so there's another variable?
The topic of the thread starter ...

quote:

Originally posted by A Hudson:

Noticed my pedal was drifting ever so slowly to the floor, ... then the "while you're in there bug" bit me ... A daunting number of choices out there ... wanted to pose this to the experts ... all advice gladly accepted.



Adams left it "wide open" more or less for advice regarding the drifting pedal and/or advice regarding upgrades within his parameters. We don't want to hi jack the thread and change the topic into one focused on SACC Restoration's rear brake kit.

Scott/Chris the brake kit is a new product, and I think there are enough people interested in it, you could start a new "announcement" thread ... and people can fire all their questions at you there.

I think the discussion about the proportioning valve may result in this thread becoming a sticky. I enjoyed the banter with Mike, didn't you? But beyond anything else I want to make sure our friend Adams gets the help and answers he's looking for.

Thanks to everyone for contributing toward making this forum the friendly and informative place it is. Building a global community is what its all about. DeTomaso owners around the world reaching out to help one another, sharing information and experience, and building relationships. Seeing people come here week after week and receive the help they are looking for makes it all worth while for me, as I hope it does for you too.

-G
quote:
We don't want to hi jack the thread and change the topic into one focused on SACC Restoration's rear brake kit.

Scott/Chris the brake kit is a new product, and I think there are enough people interested in it, you could start a new "announcement" thread ... and people can fire all their questions at you there.


I completely agree. I will start a new thread and answer the questions that have been posted already in the new thread.

Thanks Adams for starting a great thread. I have really enjoyed the discussion thus far.

Take care, Scott
Mike, the rear wheel lock-up that was experienced by one of the '70's test cars likely had more to do with the Pantera's suspension design, spring rates and shock valving than brake bias. Since the Pantera's front suspension has no "anti-dive" designed into it, with the original soft springs and shocks, in an all out panic stop, the nose of the car drops and the back end rises, causing significant weight transfer onto the front end. This weight transfer increases the load on the front tires but also lowers traction at the rear end.

This is another reason why the arguements for and against removing the factory pressure reducing valve aren't as simple as merely altering brake bias.
quote:
Originally posted by David_Nunn:
Mike, the rear wheel lock-up that was experienced by one of the '70's test cars likely had more to do with the Pantera's suspension design, spring rates and shock valving than brake bias. Since the Pantera's front suspension has no "anti-dive" designed into it, with the original soft springs and shocks, in an all out panic stop, the nose of the car drops and the back end rises, causing significant weight transfer onto the front end. This weight transfer increases the load on the front tires but also lowers traction at the rear end.


A fascinating point. I hadn't considered it, but I think it's quite valid. So, a Pantera fitted with aftermarket shocks and stiffer springs would then have less nose-dive, less weight transfer to the front, less loading on the front wheels relative to the rear wheels, and therefore would benefit from increased rearward brake bias over stock--not a radical decrease in rearward brake bias.

Thanks for bringing that additional point to light! applause
"a Pantera fitted with aftermarket shocks and stiffer springs would then have less nose-dive, less weight transfer to the front, less loading on the front wheels relative to the rear wheels"

Here's a great link to a website that actually shows what happens with anti-squat/dive suspension geometries....click the tabs on the top and it will run through an animated change in the Center of Mass/Gravity and the change that takes place, on the right top corner there is a play arrow, a stop and forward and back arrow to stop the animation.
http://www.racecartuner.com/03/305.html

I wouldn't have thought that with less dive there is that much difference in weight transfer or loading, but there is. Also you would certainly have less suspension geometry changes and therefore fewer changes at the tires contact patch, which in turn keeps more tire on the road giving better grip when braking. Wow...what a great discussion!
6018 is lowered about as low as you can go, it has Koni coil overs with Hyperco springs. It doesn't nose dive. It brakes flat. The front springs aren't that stiff, the car rides very nice, absorbs bumps very well. I don't think its the springs that have eliminated the nose dive, I think lowering the car is responsible for that.
When the car sits down front and back (when you brake) and it does not lock up, then it is balanced properly.

If the nose is diving under braking and the rear is "in the air", there is insufficient braking in the rear.

This is easier to see in an autocross car rather then a high speed track car because of the differences in speeds, but you are aiming for the same thing.

Oh, and for a performance car, you should be able to stand on the brakes, literally, and not be able to lock up the brakes.

This is how the street 65-6 Shelby GT350 brakes are set up. It is virtually impossible to lock the brakes up.

I doubt that the Pantera needs more then a 11.75 to 12" front rotor. Granted with the 17" rims those would look silly, but I don't think you need 14" front rims.

You can debate what the front thickness should be but 1.25" vented would probably be maximum. I happen to like that rotor.

A 67 Thunderbird rotor will substitute for the stock P on the P hub. It is 1.25" thick and 11.75" od. Of course you can go with a aftermarket composite also but they start to get pricy in this size, particularly plated/slotted/cross drilled.

You can open a can of worms with a 1.25" rotor. For one thing you need to micro cut the rotor on the car because of the mass. If it is the slightest out of balance, you won't be able to drive the car.

Probably 1" in the front, vented, is less problematic for a street car. The size of the pad, surface area, and the compound are important.

I like the Porterfield RS-4 compound. The R-4 is a race compound and you don't really want that on the street.

The rear is a different story rotor size wise.

I happen to think that the 68-9-0 Mustang front rotor is about right for the rear. 11.3"od x .81" thick vented. Too bad we can no longer get the original configuration, i.e., the current replacement rotor has the bearing hub cast into it. Probably a Willwood modular rotor in that size would be the substitute to use?

The 4 piston Willwoods front and rear is a great way to go. 6 piston in the front is nice but maybe a little to Lemans orientated then necessary?

Sure, because of the four mounting points on the stock P rear uprights, that opens the option of using the P original caliper as the parking brake. Actually a good idea.

This is probably how I will go on my Pantera.

I already have my GT350 set up this way with a 1-1/4" bore master and the setup is NICE!

The difference is the Shelby uses a 67 Tbird caliper. It is heavier and larger then the Willwood but it is what the vintage racers use on their cars and it is what "the factory race cars" used. It is very street-able since it came off of a production street car.

It is a brake system that was designed to stop a 6,000 pound car. It works on a 3,000 pound car twice as well.

Save the stock P front "proportioning valve", but have it mounted and bronzed and put it on the mantle. For this kind of a braking set up you need an adjustable proportioning valve for the rear.

It shouldn't be difficult to do. The Pantera unlike the Mangusta is inherently stable. It should just be a matter of getting the pressure just right?

I think the relative ease of "upgrading" brakes on this car as demonstrated by the number of vendors who have done it shows that.

I think the difficult and maybe dangerous part of this process is going to be building the adapter brackets for the car.

Maybe it is best to leave that to someone who can use his CAD program and, what is it now, a plasma cutter, to whittle them out of 1/2" plate? Wink
Eliminating "nose dive" under braking is a product of correct shock absorber valving combined with proper brake balance. Stiffer springs and a lowered center of gravity help too. That being said, these improvements only make the car able to deal with the weight transfer that's occurring, without upsetting its balance and traction.

Here's an article on weight transfer and anti-dive suspensions, written by Terry Satchell, chassis specialist for Ford Motorsport:
http://www.circletrack.com/tec...arameters/index.html

It's impossible to eliminate weight transfer under braking. In fact, weight transfer also happens when you push down, or lift off of, the throttle, and it affects traction whenever it occurs. If you are lucky enough to attend any of the well known high performance driving schools (Bondurant, Jim Russell, Skip Barber, etc.), weight transfer is usually the first day's lesson.
I had no idea this discussion would become this lively, informative, passionate. Thank you to every word. Just returned from a family trip (National Championship Game, Roll Tide) and didn't see this latest round til today.

Sounds like a new less aggressive rear kit may've been spawned. And a super discussion tributary on springs, shock rates, lowering, nose dive/weight transfer.

Now comes the fun part... doing it. Thanks folks, very much. PI membership pays off again!
Since the consensus seems to be that the rear stock caliper is inadequate here is my idea for a upgrade. Due to the availability of stock calipers why not use a pair of front calipers on the rear. Use the stock rear caliper for the E-brake and make up a bracket to fit the front calipers in the rear. Do the proportioning valve mod in the front, and put a ajustable proportioning valve in the rear circuit. Has anyone tried this and your thoughts?
quote:
Originally posted by MANICAL:
Since the consensus seems to be that the rear stock caliper is inadequate here is my idea for a upgrade. Due to the availability of stock calipers why not use a pair of front calipers on the rear. Use the stock rear caliper for the E-brake and make up a bracket to fit the front calipers in the rear. Do the proportioning valve mod in the front, and put a ajustable proportioning valve in the rear circuit. Has anyone tried this and your thoughts?


My thoughts exactly...and move the front rotor to the rear along with the calipers.
IMHO the main reason for NOT using two inadequate calipers in the rear is, they are heavy and still ineffectual even when doubled up. Just because it's easy to do doesn't mean it's worth the effort. I can't be sure but I think Goran is only using the stock rear calipers for an easy solution to an e-brake- required for legal road cars. FWIW, stock Pantera rear calipers were also used on the Peugeot 205.
quote:
Originally posted by Bosswrench:
IMHO the main reason for NOT using two inadequate calipers in the rear is, they are heavy and still ineffectual even when doubled up. Just because it's easy to do doesn't mean it's worth the effort. I can't be sure but I think Goran is only using the stock rear calipers for an easy solution to an e-brake- required for legal road cars. FWIW, stock Pantera rear calipers were also used on the Peugeot 205.


The thought was to use the existing rear caliper for the handbrake, and relocate the front rotor and front caliper to the rear.

Are you saying that the existing front caliper and rotor are inadequate for the rear?

Considering the size of some of the wheels and tires being run on these cars converted to Gp4 fenders, the added weight of front caliper in the rear has to be insignificant compared to the added weight added by a 18"diameter x 13"wide rim and tire? I think I remember the front caliper to weigh 4 or 5 pounds? No?
quote:
4 or 5 pounds? No?


They weigh 14 pounds each.

Why not use the kit I put together. Simple, easy to install and inexpensive??? And everyone that has used it says the improvement is fantastic. The car squats rather than diving when the brakes are applied...

Putting the front rotor on the rear introduces additional issues because the diameter and thickness is different.
quote:
One of my criteria is getting away from the original rotors just because of replacement costs.


We developed the Caliper Upgrade Kit because others had said they want to KEEP the stock rotors.

We also offer many kits that replace the stock rotors with aftermarket ones. BUT, the biggest bang for the buck remains the rear caliper upgrade...
It definitely is a good deal. I have other considerations though.

There is pressure on the brake manufacturers to bring back the Mustang brake rotor as it was made originally.

I don't think it is if, it is when.

I would adapt that vented rotor to the rear of the Pantera, and the 67 T Bird rotor to the front.

That will make affordable, or more affordable rotors available for "hobby" racing.

Selecting the calipers then is just picking the combination out of one of the aftermarket calipers like Wilwood, and making an adapter.

For me, overall, that is a better combination.
o
quote:
Originally posted by PanteraDoug:
One of my criteria is getting away from the original rotors just because of replacement costs.
I saw a Trans-am Mustang go through 4 sets of rotors and pads in "practice".

That is just not affordable with stock Pantera rotors.
Hello Doug; The Trans-am Mustang going through that many sets (4) of pads & rotors would indicate to myself that the current braking configeration is woefully under-designed, also worth noting is the intense heat build-up of the current system makes the brakes extremely "Fade Prone"....it would be the same if the car was blowing up transmissions, or snapping drive shafts...the brakes are over-stressed/taxed....brake fade into a hair-pin turn does NOT equate into the Checkered Flag.....Mark
quote:
Originally posted by 1Rocketship:
o
quote:
Originally posted by PanteraDoug:
One of my criteria is getting away from the original rotors just because of replacement costs.
I saw a Trans-am Mustang go through 4 sets of rotors and pads in "practice".

That is just not affordable with stock Pantera rotors.
Hello Doug; The Trans-am Mustang going through that many sets (4) of pads & rotors would indicate to myself that the current braking configeration is woefully under-designed, also worth noting is the intense heat build-up of the current system makes the brakes extremely "Fade Prone"....it would be the same if the car was blowing up transmissions, or snapping drive shafts...the brakes are over-stressed/taxed....brake fade into a hair-pin turn does NOT equate into the Checkered Flag.....Mark


It is a result of too much practice for a 20 minute race. 3 sessions a day for three days, THEN the race.

It was also on the Full 2.5 mile course at Virginia International Raceway. The course they normally only use for the motorcycles.

The course is fast and when you are running with the Ford MkI's and II's flat out, you tend to use up your brakes a little?

Pantera's would have a tough time with this because of the rear disc setup on the car.

The race trailer has a lift and an on the car rotor machine but you need to have something left to cut.

If you look at the pictures of the Gp4 cars they have 12 x 1.25" vented rotors all around. That helps some.

Those are also the Lincoln/Thunderbird rotors, at least originally that was the source, so they are as economical as you can get. Throw them away when you are done with them.

They are big enough that you need to micro cut them new on the car and index them to reduce the vibration from them on the car because of the inertia.

A bigger front spindle on the Pantera would help some for bearing longevity. The stock Pantera spindle is the size of the early Mustangs. The Trans-Am Mustang race cars use the 1970 and later spindle which is larger in outside diameter and helps a lot with wider tires and wheels.

There is no such animal for the Pantera.

No one here really wants to hear it, but if you compare the front end components on the Mustangs and the Pantera, it appears that the Pantera components are modeled after the Mustangs.

A lot of current cars use aftermarket 2 piece rotors and hubs. No argument from me on that but Wilwood's are not the preferred rotors of the racers I talk to?
Hello Doug; Appreciate your insights & thoughtful response. Do you see much Ceramic braking systems at the track?..Also I feel it is NOT disparaging to point out flaws in the Pantera, is the Pantera a "Perfect" car?!....NO far from it, but it does provide it's owners a "Nice" platform to improve upon!!!....Interesting fact about the GT40's tremendous success at LeMans, was vastly attributed to the Ford engineer that came up with the system that allowed the rotors to be changed out in 10 minutes.....Mark
quote:
Originally posted by 1Rocketship:
Hello Doug; Appreciate your insights & thoughtful response. Do you see much Ceramic braking systems at the track?..Also I feel it is NOT disparaging to point out flaws in the Pantera, is the Pantera a "Perfect" car?!....NO far from it, but it does provide it's owners a "Nice" platform to improve upon!!!....Interesting fact about the GT40's tremendous success at LeMans, was vastly attributed to the Ford engineer that came up with the system that allowed the rotors to be changed out in 10 minutes.....Mark


Yes it is a nice platform, and it comes from quite a blood line. I like it.

Ceramic on the pads do you mean? Porterfield R4 on the track and R4S on the street is what I see everyone run.

I use the street pads. A little pricey though.
I only know the Vintage Racers. They are restricted by the rules to what they can run. I never heard of ceramic rotors being used by any of these cars during the era.

The Mustangs all seem to be using the Trans-Am Mustang brake setups that are outlined in Fords "Boss 302 Chassis" racing booklet, Stage III.

They apparently are allowed substitutions like the two piece rotors but they are all using the big Lincoln calipers with the Porterfield race pads, F250 master cylinder with 1-1/4" bore. Rotors are vented 12x 1.25".

Ceramic rotors I think are current technology for the current slot cars.

In some cases racing Vintage is like comparing a canvas skined bi-plane to the Space shuttle, but that's kinda in the point.

There is a little of that here with the Pantera, as far as how the owner conceives of his car I suppose.

It's kinda like a 60 year old guy hanging out at the bar trying to impress 20 something women. I guess some of the girls need glasses?
Hello Doug; I didn't realize that "We" were discussing "Vintage Racing", as I now understand. How is it possible for the Pantera/s to run Thunderbird rotors in "Vintage" if that was NOT Factory installed/equipped?!....or for that matter..."Any Changes/Alterations"?!....Mark
quote:
Originally posted by 1Rocketship:
Hello Doug; I didn't realize that "We" were discussing "Vintage Racing", as I now understand. How is it possible for the Pantera/s to run Thunderbird rotors in "Vintage" if that was NOT Factory installed/equipped?!....or for that matter..."Any Changes/Alterations"?!....Mark


Gp4 cars ran them in the day. Look at the pictures of the brakes on the "Candy" Gp4. They show them pretty clearly.
Has anyone tried these pads for their stock, rear calipers?

I think they have the correct form factor (although they would not have the correct piston stop on the back of the pad).

I know... "Stock Rear Calipers Suck"...

But that's what I have now, and the organic pads wear very quickly.

POTENTIAL replacement for stock rear pads


For those with deeper pocketbooks, the Porterfield GD535 pads are recommended.

To take it to the Next Level, read the front of this thread for contact info for vendors selling 4 piston rear caliper upgrades (but you still have to keep your stock calipers if you want an e-Brake, or the price goes up again for the IPSCO or other eBrake system).
The problem is that even the Porterfield R4s street pads are very hard compared to a "metallic lining".

What you will feel with them on the street is a seemingly unresponsive pad until you get them warmed up.

That's the "s", street pad too. The race pad, you would likely kill youself and someone else with. Those need to get nearly red hot to work at all?

So far I am still searching for a pad. The HD "taxi cab" compound pads may be the best compromise?
Rocky, a few people (very few!) have adapted rear pads from the Porsche 914 to stock Pantera rear calipers. Then 914 rear pads can be had in several compounds from places like PelicanParts.com. Virtually no one makes performance pads for the Peugeot 205- which is where our stock rear calipers were sourced.

Finding the right compound for your driving use & style will be a try-it-and-see exercise that may cost more than changing to real rear calipers & vented rotors. And the stock Pantera brake plumbing biases more pressure to the rear while the excellent fronts are mostly along for the ride. This is exactly backward to all other cars on the road, for reasons known only to Ford engineering. To do what you want WILL require some parts swapping.... or going slower.

On the 914, their rear pads sort-of work OK but that car can be 1000 lbs lighter than your Pantera. So don't expect miracles: you need new pads to work better without wearing out the rotors too fast; normally you get one or the other. I would CALL Porterfield in CA on the phone and discuss options.
The graph actually confirms what I am saying about the Porterfields.

You need to get them hot to make them work. 300F is very hot if you ask me.

This doesn't build confidence in the brakes when you jump in the car and just want to go around the block in it.

It would actually be nice to see that graph continued with other alternatives in comparison but I think the source IS Porterfield themselves.

I think to put the temps in perspective, header tubes will start to glow red around 700 degrees.

The temps needed to be "effective" for what you paid for concerns me in say a wet driving scenario where the rain is keeping the brakes from even warming up to 300?

As BWrench says, it really is a matter of testing different pads to find what you like?

Looking at the chart again, there isn't much difference between the R4 and the R4S as I read it and the R4's are DEFINITELY just plain dangerous on the street.

Not everything "high performance" is better. Wink

Wow. I am new to Panteras and by far no expert on brake systems so that renders me unqualified to comment.

What I do know and have seen from my years in aviation is that often a manufacturer will sacrifice performance to bring their product into line with the ability of average or below pilots / drivers. Most are not professional drivers or driving on a track at excessive speeds. I am sure the Tamaso engineers applied a lot of thought and experience when designing the brakes system. I would bet that the valve was used to make the system safer for the average driver in average conditions and was a cost consideration so those alone would leave plenty of room for performance improvements. But how many of us are going to throw their metal mistress around to the point of experancing true heat induced brake fade ? Not me. Those days are in my past and the car is too valuable.

Also what is good on a race track is not always good for a street machine. Putting a NASCAR engine in your Pantera would make a miserable street machine of which you would probably never realize the performance aspect. You want to pay how much for what ? I remember one of my customers complaining that his Fararri needed a $13,000.00 brake job. He said that the car seldom sees fourth gear in LA but you gotta have brakes.

It is a owners prerogative what they do to their car but a guy like me without unlimited funds has to consider upgrades in a cost to real world benefit ratio. I don't need ceramic or carbon fiber brakes. I would much rather have a anti skid system for the cost. Of the brake system upgrades available the ones I would never consider are those that eliminate the emergency hand brake. NFW that's race track stuff not for a street machine.  Be smart and think safety because of all things Pantera as with all cars brakes are number one. If you have ever driven ice you'll know that helpless feeling of no brakes.

Hurst/Airheart, a leading manufacturer of racing brakes, tested the OEM Pantera brakes back in the 1970s. The first stop from 60 mph required 219 feet and 225 pounds of pedal effort, which is an extremely high amount of pedal effort. With each consecutive stop both the braking distance and the pedal effort decreased. Upon the eighth consecutive stop the Pantera achieved its advertised stopping distance of 133 feet (from 60 mph), and pedal effort had fallen to 115 pounds. Of course, in a “real world” situation such as a “panic stop” a driver does not have the opportunity to “pre-heat” the brakes with seven practice stops.

As the test progressed brake-fade set-in with the next (ninth) consecutive stop. There was therefore a fine line between optimum braking performance and the on-set of brake fade. One last point I wish to mention, Hurst/Airheart concluded from their test that a Pantera’s ultimate stopping capability had the peculiar trait of being limited by the brakes, rather than being limited by the amount of traction provided by the tires (PI News, volume 3, no.4, pages 27-32).

Citing this test, Pantera International’s founder Fred Matsumoto referred to performing a panic stop with the Pantera’s OEM brakes as a religious effort; he wrote you stomp on the brake pedal and PRAY that you stop in time (PI News, volume 14, no.2, page 14)!

It befuddles me that these are the same brakes that some magazine testers praised, in fact one tester described them as “the best production car brakes in the world” (Motor Trend, March 1972, page 106).

Doug, be mindful of the fact that your GT5 is equipped with the same brakes as the Group 3 racing Panteras, the brakes are quite a bit better off than those fitted to the Ford Era narrow body versions.

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