79-93 Mustang rear disc brakes

[mw85gt]

The GCR spec line table for 79-93 Mustangs permits the use of the M-2300-C rear disc brake kit. I thought the M-2300-C rear disc brake kit was basically the rear brakes from an '87-88 T-bird turbo coupe; single piston Varga calipers and 10" vented rotors. The spec line table also allows 12.2" rotors. How is this rule typically interpreted?

The 2300-C kit is 94-04 Cobra rear brakes. Single piston Varga caliper with 11-inch vented rotors.

[jimwheeler]

Remember the newest brake rule allows:

j. Rear calipers: Any ferrous or aluminum caliper using four or
fewer pistons and using one brake line per caliper.

12.2 x 1.25 vented discs

You can use anything within those parameters. This gives everyone, in all cars, the same brake capability. The other deal is just left over, from when they authorized brakes by part number.

wheel

While the GCR does allow for the 4 piston & 12" brakes, my personal experience (with a Wilwood bolt on kit) that it is WAY too much rear brake for a Mustang. Wilwood tech went to great lengths to make the kit work, including exchanging the calipers that came with the kit for ones with smaller pistons, but I still have almost all the rear brake dialed out with the proportioning valve. "Fast" Andy experienced similar problems with his 4 piston rear kit.

My buddy Scott, whose Mustang is nearly identically prepared, runs single piston PBR rear calipers (The Ford kit I believe) with zero problems. We both run Wilwood Dyna-lites up front, and his car easily brakes as hard as mine.

Mark W.

I use Brakeman front calipers (which will stop a freight train) and I kept those single PBR rear calipers.

I would run out of rear brake after just a few laps.

So heres what I did:

I added a rear vent hose to feed air to the rear calipers that mounted off the bottom of the lower trailering arm. Now I would only move the valve to about 1-1.5 turns toward the rear as the race progressed. So that helped tremendously.

But then it started wheelhopping in the rear:

So I added additional bracing to the stock caliper mount, you need better bracing than you get from the kit, it's not adequate and the flexing caused wheelhop.

Next the pads wore uneven. So I found the calipers would clam shell after about 5-6 races so you needed to buy new ones regularly...but they are cheap.

Next I saw witness marks on the brake mounts (from axle flexing). This flexing makes it tricky when trail braking into bumpy corners like Turn 17 at Sebring. Be sure you use the 31 spline axles, that cured that.

Oh and thank the lord for Castrol SRF fluid (previously used wilwood). I had many close calls until I discovered that stuff. You would run down a long straight with the venting system cooling the rotors and blowing this hot air on the caliper and it would just start just boiling the fluid. You would go for your brakes on the next corner after a long straightaway (that was supposed to cool off the brakes..but heats up the caliper)..... and the brakes were gone. So buy the fluid.

We also added those nomex spark plug boots to our brake transfer tubes on the front.

Solid brakes from then on.

Patrick James

[jkopp]

Originally Posted by PRO SYSTEMS

Oh and thank the lord for Castrol SRF fluid (previously used wilwood). I had many close calls until I discovered that stuff.

I agree 100% with this. We switched to SRF this year. It's one of those situations where you're kicking yourself wondering why you didn't do it a long time ago. Worth every cent!

[jimwheeler]

If the brake/clutch master cylinder rule passes this week, you will be able to tune the rear brakes exactly to your liking with the balance bar. The brake line restrictor deal can be a thing of the past.

I currently run the stock rear brakes and tune by using different pad compounds and with the brake pressure restrictor. Actually just restricts the flow, not the pressure. It works OK, but not the best system.

wheel

[Mark Allen]

One other item to consider, the typical brake pressure limiting valves don't limit to zero. Some people have put two thumbwheel limiters in series to get the performance they want. Just a thought.

Mark

[t4wallace]

Originally Posted by Mark Allen

Some people have put two thumbwheel limiters in series to get the performance they want.

That would be what we did to "band-aid" the performance issues...

As was said here, that would all change if the brake rules creep.

[jimwheeler]

You mean, that would change if the brake rules are improved?