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.

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