Skip to main content

quote:
Originally posted by ZR1 Pantera:
I also have mine apart. The front measures just under 11.125 and the rear measures just over 11.625. So know the question is why are yours smaller than mine???


It's a very good idea to install an adjustable front/rear proportioning valve.

You are going to have to readjust the ratio.

Stock the brakes do not lock up and the rear will not come around.

Give the rears more brakes and for sure the cars rear will lock up and that means the rear will swing out on you. Maybe even in just 30 mph traffic.
quote:
Dave what size tire do you run? I'm running 245-40x17 front....maybe I should go for a little less powerful caliper than a 6 piston.

I definitely planned on putting an adjustable proportioning valve in. Ideally I'd like to see if we southern cal guys would want to rent a skid pad someday to test swaybars and brake bias adjustments.


Tom,

I have 14inch 6 piston front rotors/Calipers and 13 inch 6 piston rears.

Increasing brake performance doesn't do a bit of good if you can't put the extra performance to the ground. It makes no sense to de-tune the front brakes because they lockup to easy. It makes better sense to get stickier tires OR remove the booster if the brakes are that good.

You can't go wrong with the 6 piston setup. Just make sure your tires are adequate.

Scott
I am a believer that the reason the brakes exist as offered was to make the car as foolproof to drive on the street as possible.

Ford had plenty of input into the Pantera and the edict from them was that there could be no way that they would finance Detomaso and sell the Pantera under the Ford logo if the car was going to understeer like the Mangusta did.

Putting the small brakes on the rear was part of the safety net built into the car.

Understeer was also.

The last thing Ford needed was a travasty similar to what happened with the new Ford GTs.

The current Ford GT Registry is indicating that as much as 40% of these cars were wrecked with under 500 miles on them.

Most of those were one car wrecks with people running into trees and poles thinking just because they could buy the car that made them AJ Foyt.

I think Ford did the right thing initially with the Pantera.

Putting more brakes on this car now isn't that simple. The panic handling of the car as far as going straight in braking will be effected.

Putting more brakes in the rear without balancing that to the front probably will be lethal.

Not everyone is going to have track time available to them to dial in a brake proportioning valve to balance.

Also you don't want to be able to lock up the front brakes in panic stopping.

The key as proven with anti-lock brakes is to keep the car straight even at the cost of longer stopping distances.

Just my opinion of this subject.
quote:
Originally posted by Tom@Seal Beach:
Dave what size tire do you run? I'm running 245-40x17 front....maybe I should go for a little less powerful caliper than a 6 piston.

I definitely planned on putting an adjustable proportioning valve in. Ideally I'd like to see if we southern cal guys would want to rent a skid pad someday to test swaybars and brake bias adjustments.

I have 225/45-17 Michelins. Any system you devise must be adjustable in some way.

It makes no sense to just chuck perfectly good tires in the effort to tune the braking performance. Put in a $40 valve and twist a knob. Easy!
De-tuning the brakes because they lockup, is like removing power from the engine because the tires break loose under acceleration.

Yes, an adjustable proportion valve is a good idea to adjust brake balance. Once the brake system is balanced, locking up the tires is either poor driving skills or poor tires IMO...

No offense intended (I mean this sincerely...)
quote:
Originally posted by ZR1 Pantera:
De-tuning the brakes because they lockup, is like removing power from the engine because the tires break loose under acceleration.

Yes, an adjustable proportion valve is a good idea to adjust brake balance. Once the brake system is balanced, locking up the tires is either poor driving skills or poor tires IMO...

No offense intended (I mean this sincerely...)


I don't know that I am disagreeing with you as much as I am debating this with myself.

If you have ever driven a 65 or 66 Shelby GT350, you would discover that it is absolutely impossible to lock up the brakes.

If you look at the brake rules discription for the 68 and later (into the '70s) rules for the GT cars like the Gulf (John Wyer era GT40), Lola T70, Porsche 930, the size of the brakes are limited.

You can play with rules like this as a ruling body to make cars more competitive. If you look at those cars and compare them to the Can-Am cars, there really isn't a tremendous difference.

There is a difference in safety factors though. The Can-Am cars are just plain lethal, as proven in their mortality rates, and the GT's have a better record as far as less people killed.

Now, they didn't restrict the size of the brakes to get less stopping, they did it to make the drivers less daring and drive within the car, and not outside of it's limitations.

The Can-Am cars had huge brakes, reduced weight, and huge horsepower engines, for their era. 600hp then was not obtainable by everyone. Now more than that is in street cars.

The formula didn't work. They ran off the tracks in the corners and into any obstruction they could find.

Granted these were crude days of air effect wings. They were there but compared to the computer controlled wings that change as the g loads and speeds did, like in Formula 1 now, they were pre-school, pre-science projects.

What I am saying here, is that there is a real issue with inability to put enough tire on the car, a real ability to put a lot of power into the car.

I'm not sure that I am capable of balancing the mechanical sciences here.

In retrospect, looking at how these limitations were built int the original car, I have to seriously consider the solution.

Fact is with a box stock Pantera, virtually ANYONE who can drive a stick, specialized in the Pantera's case as it is, can get into the car and drive it really fast, over 125 mph the first time, like it is nothing, like it is doing 55 mph.

Just like there is a practical horsepower limit to these cars, in that over a certain number the car just won't go any faster, there is a practical limit to tires, and BRAKES.

This is my thought on the entire subject, other to say that I'd have to reserve judgement on driveing a Pantera, really hard, that had these upgrades to make a rational decision on where to go with the solution.

I like the idea of the 6 piston Wilwood caliper in the front. I agree that 1.25" thick rotors are there for race durability reasons and are no where needed even marginally on the street or even tracked street cars, but where to go on the rears is another unknown all together.

Now if I could just find a factory Gp4 car owner that would let me take a few laps just to see if I liked the entire package concept of it... Big Grin

BUT these are the issues that keep me busy and rarely bored.
Last edited by panteradoug
Doug,

What is happening here? I am in complete agreement with you AGAIN! Cool

I think part of the problem with safety is anyone can get a car like ours, put a huge high horsepower motor in it, with huge brakes, and then their testosterone kicks in. They think they are invincible. They stop thinking and believe the car can do anything. Until they wrap it around a pole.

I use to have a hi horsepower off-road car. Over the years, everybody and there mother's were getting these cars. Guys were taking 2nd's on their houses to buy a 50-80K off-road car. FOR THEIR FIRST CAR. What do you think happened to a lot of these guys. Yes, they crashed their cars. Some rolled and some people were killed. They get in a high dollar car and feel invincible.

I believe with a high horse power car and a car with race worthy brakes, you need the appropriate tires to get the power and brake performance to the ground and the driver skill to maintain control. And I agree that there are limits to both usable horsepower and usable brake performance on the street.
quote:
Originally posted by ZR1 Pantera:
Doug,

What is happening here? I am in complete agreement with you AGAIN! Cool

I think part of the problem with safety is anyone can get a car like ours, put a huge high horsepower motor in it, with huge brakes, and then their testosterone kicks in. They think they are invincible. They stop thinking and believe the car can do anything. Until they wrap it around a pole.

I use to have a hi horsepower off-road car. Over the years, everybody and there mother's were getting these cars. Guys were taking 2nd's on their houses to buy a 50-80K off-road car. FOR THEIR FIRST CAR. What do you think happened to a lot of these guys. Yes, they crashed their cars. Some rolled and some people were killed. They get in a high dollar car and feel invincible.

I believe with a high horse power car and a car with race worthy brakes, you need the appropriate tires to get the power and brake performance to the ground and the driver skill to maintain control. And I agree that there are limits to both usable horsepower and usable brake performance on the street.


OMG! What's going on here? Eeker

The fuesable link here is the tires.

It is possible to create and put on the street a true super car here.

CAN a tire be found adequate to the job?

The Gp4 cars attempted this and I suppose were successful enough.

Problem is though that those cars were raced under much closer to ideal conditions than a street car is exposed to.

Again. Maybe it is better to build very specific and calculated limitations into a street vehicle?

You can put the ultimate tire on a car, but it doesn't see the ultimate road 100% of the time.

This is all serious stuff to consider.

Don't worry. I'll keep posting until something comes up that we disagree on. It could be any minute. Smiler
Last edited by panteradoug
Finally answering Doug's question I missed from several pgs back-
"Bosswrench, Do you know what calipers were used with the 1.25 front rotors at LeMans?"

On the GR-4s, they originally used gigantic iron three-piston calipers similar to what was on the GT5 and GT5-S cars 10 years later. The smaller rear 3-piston brakes were sourced from Rolls-Royce, altered a bit for slightly larger rotors in back. GR-3 Club-racers also used iron 3-piston Girlings on all 4 corners, with the later pair-of-pliers e-brake system. These Girlings are incredibly heavy: when I mounted up a genuine GR-3 brake system on a '72 Pantera Judy & I were racing decades ago, I had to use both hands to hold one caliper!
ALL the race cars used 15" wheels and are still required to today by the vintage rules. So the 1.25" thick 'race' rotors are virtually the same OD as our 0.81" thick steet rotors and thus have the same mechanical leverage. Far as I remember, failing front bearings on gr-3s & GR-4s were not the problem; breaking stock rear axles after 3-4 hrs of track running was (and still is today)!

On spindles: early pushbuttons used a different casting in which the spindle was removeable; the spindle had a taper held in by a big nut on the backside. I suppose if one had such an upright, you could have a replacement spindle made of better steel & with bigger bearings. Not a direct swap: the early uprights used integral steering arms while all later front uprights use removeable steering arms & integral spindles. Dunno what front bearings were used on the earlies. But as Steve W said, that spindle is no longer generally available except as recycled parts from junkers. Early car's mating a-arms were different (wider), too.
Thanks for your input BW.

This is one of the things that was very hard to research.

I finally came to the conclusion that some of them had the aluminum Girling 18/4, 16/4 units, front and back.

This is what the 68 gt40 "Gulfs" ran. The earlier GT40's ran the aluminum Cobra Girlings.

In investigating it appears that the front has the same braking power as the stock caliper. It is used so they could use a 1.25" thick rotor for race reasons. They don't give greater braking power though.

The rears 16/4's were used for the same reason, to use 1.25" rotors.

Aluminum on these calipers helps tremendously.

I can't immagine why they ever used the iron Girlings on the race cars to begin with.

I can make you a better set up with the big Lincoln calipers and T-bird rotors. Wink

That set up would really be nice with aluminum calipers. Don't you know some of those showed up on the race cars too? Wink
quote:
The Can-Am cars had huge brakes, reduced weight, and huge horsepower engines, for their era. 600hp then was not obtainable by everyone. Now more than that is in street cars.

The formula didn't work. They ran off the tracks in the corners and into any obstruction they could find.


Not sure I would describe the brakes on CanAm cars as massive. My McLaren M12 came standard from Mclaren with only a 12" vented rotors front and rear with Girling 16-3-LA Calipers. These relatively modest rotors and calipers had a huge advantage in their application...the M12 weighed in at ONLY 1300-1400 pounds total...so you didn't need such huge brakes. The CanAm car had the same wheel size limitations we do as they ran 15" wheels and tires. Can't comment on what the Lola's or Shadows or other CanAm cars were running for brakes but since the McLarens dominated from 66-72 when the turbo Panzers came on the scene, it's safe to assume that the McLarens had the best of the best.

As far as the Can Am formula not working??? HUH? So today's F1 formula doesn't work also because they run off corners and hit tire barriers too? The CanAm cars were on the edge of so many major break through's in automotive design...this one series probably advanced automotive engineering more than any series (IMO). It was unlimited in design restrictions. The reason they went off the track is because they were at the edge of aerodynamic stability. Read about problems caused by "wake turbulence" while running behind another car, it moved cars across the track...it's wasn't a braking problem. Or they would use too much throttle over a rise on a high speed section of the track causing the nose to lift 1/2 to 1" at 150+mph and the car turned into a wing, like so many cars do today. My M12 would do 0-100 mph and back to 0 mph in about 8 seconds and the I know that under braking there were more G's developed than under acceleration.

Think of how much more sheer braking power Scotts Pantera has today compared to the CanAm cars!!! But it's all about weight(IMO). The McLaren F1 cars of that era were only running 11" rotors, but the cars weighed a mere 1100 pounds!

quote:
Just like there is a practical horsepower limit to these cars, in that over a certain number the car just won't go any faster, there is a practical limit to tires, and BRAKES.


Totally agree here. For those of us with narrow body cars we can't just shove more rubber under the car to offset too much braking capacity. We're stuck with 225's to 245's in the front unless we flare the car, and up to a 335's in the rear. I'm running a 245-40/17 front, 285-40/18 rear. I'll be less prone to lock up in the front when compared to a 225 tire...but am probably much more likely to lock the rear tires compared to someone running 335's, hence my need for a bias adjuster. Could I throw a 335 under the rear, yep, but I'd rather go smaller to keep balanced understeer/oversteer on handling given the limits of my front tire size.

Everything is balance...too bad we have to work normal jobs....sure would be fun to have a 20-30 person team with unlimited $$$$ engineering and testing all these combos. Sorry I'm dreaming again. Great discussion!!
Last edited by tomsealbeach
quote:
Just a comment about front brake performance. I have the Byers, Willwood 4 piston calipers and hats all around, and the larger rotors up front. Had to add a proportioner (pressure reducer) on the front circuit because the front brakes were too powerful. Locked up easily.


Dave, do you have a picture the proportioning valve you put in - how and which?

I have the same set-up from Byars as yours - and the same problem with balance towards the fronts.

Thanks
quote:
Originally posted by Push1267:
quote:
Just a comment about front brake performance. I have the Byers, Willwood 4 piston calipers and hats all around, and the larger rotors up front. Had to add a proportioner (pressure reducer) on the front circuit because the front brakes were too powerful. Locked up easily.


Dave, do you have a picture the proportioning valve you put in - how and which?

I have the same set-up from Byars as yours - and the same problem with balance towards the fronts.

Thanks

It is a simple Wilwood unit. It is between the front master output and the front brake line. I believe I have mine turned down 6 full turns.

http://www.summitracing.com/parts/wil-260-8419

Attachments

Images (1)
  • wilwood_prop
quote:
Originally posted by 1973 Pantera:
Does anyone have any documented incidents of any Pantera spindle failures over the last 40 years?

I've never heard of one.


Yes. There have been examples of outer bearing failure and spindle failure on Pantera front uprights on race cars. But failure is only one aspect to consider in race conditions. The other is flexing of the hub assembly relative to the spindle. For race cars you need go minimize this to improve handling and steering. To solve this problem (improve handling, steering responsiveness and eliminating bearing failure) you can fit a spindle stiffener, larger bearing hubs and a bearing spacer to set the pre-load. You can buy these kits with chromemoly hubs from www.msfracingcomponents.com.au

Fit once and never worry again.
Doug wrote- "Aluminum on these calipers helps tremendously.
I can't immagine why they ever used the iron Girlings on the race cars to begin with."

It was a 70's/'80s thing. Early aluminum calipers were quite light compared to iron, but nowhere near as stiff. Alloy calipers flexed enough that heavier iron calipers were sometimes retrofitted in race cars to control pad skewing and odd/premature wear patterns. Nowadays with computerized FEA to predict what will happen under race conditions, places that make aluminum race calipers have the best of both: adequate stiffness AND lightness. But 40 yrs ago, not possible.

DeTomasos still sometimes lose front wheel bearings on the street at more-or-less legal speeds, but its usually due to lack of grease and/or service. OEM front wheel bearings are the same p/n as mid-'60s Ford 3/4 ton pickup trucks, so I don't think bearing strength is the issue. I've been on runs where stone-stock Panteras and Mangustas lost front wheel bearings (same part#, BTW), and from a yard away you could smell burned grease. OEM wheel bearing nuts used race-inspired 'staking' to set bearing clearance, and were one-shot-only. At $16 each, most guys tried to get more than one use out of them, often with bad results. Later, Ford/DeTomaso drilled the spindles (and a lot of us did, too) for cotter pins. But the OEM non-castellated nuts didn't allow much tolerance so you needed shim washers. The very late sheet-metal castellation piece with drillings, cotter pins and shim washers helped a little.

A final consideration: for a decade now, I 'borrowed' a successful design and have been scratch-building 'infinitely-adjustable' front wheel-bearing nuts for a few Pantera friends, to allow them to set exactly the wheel bearing clearances they need without drilling, cotter-pins or shims. So far, no failures.
The reason I asked is because I noticed the similarity of the front spindles on the Pantera and the 65-69 Mustangs and Cougars.

When Ford went from the 70 series tires to the 60's series there was almost immediately an issue with spindle failure.

The solution for Ford was to enlarge the outside diameter of the spindle. The racers immediately took advantage of these as well.


Similarity does not indicate the exact situation. There is a big difference between the Mustang with close to a 60/40 weight bias and the Pantera which is 40/60.



My car had the front locking nuts. It was very simple for me to change these over to the cotter pin retainer like used on the Mustang. Those bearings for me, since I have experience with those, I can get the bearing preload perfect every time on.

That is not a difficult change over at all. In fact, it is a very easy and simple one.



As far as the aluminum calipers instead of the iron, again, I noticed the difference from the street Cobras to the Comp Cobras which used the aluminum calipers.

I also noticed that some of the factory Gp4 Panteras were using the aluminum Girling 18/4, 16/4 calipers which are intended for the 1.25" vented rotors.

These are the same calipers used on the 68 and later GT40's, also know as the Gulfs.

Noted also used on other late 60's early 70's GT race cars, like the Lola T70 and the 935 Porsche. Maybe the 917 whale tales too? Something in the period rules about limiting braking ability for safety reasons? Very strange. How does that slow down the cars? The rules comity must have voted on that one at a wine tasting festival? In any event, aluminum calipers can't be all bad?



I agree that unless someone gave you a set of the aluminum Girlings for free, they are disproportionately expensive compared to say the Wilwood, the most logical way to go with brakes right now is with a set of Wilwood's and leave the existing spindles and bearings alone and just pack 'em with grease once in a while.

Even switching to the 65 Mustang vented rotors no longer makes much sense since they have become collectors items? They were just a cheap substitute for the stock Girling rotors to begin with.


The real issue is that far too many Panteras are being put away for 5 or 10 years at a time then just be pulled out of storage and driven without any maintenance at all. You need to pack the bearings annually as far as I am concerned.
Last edited by panteradoug
Post
×
×
×
×
Link copied to your clipboard.
×