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Adapting Porsche 991 cup braking system for rx7

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Adapting Porsche 991 cup braking system for rx7

Old 05-02-19, 08:07 PM
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Adapting Porsche 991 cup braking system for rx7

I have successfully installed the majority of the braking system from a 2016 Porsche 991 cup racecar into my 1993 Mazda rx7 Roadrace car.
The porsche brakes are built by PFC who won the contract to supply all 991 cup cars. Porsche held a competition and challenged all major brake manufacturers (brembo, ap, etc) to meet their criteria. The parts had to withstand 600 stops from 190 mph down to 60 mph without cracking. PFCs first design failed at 450. They made 7 changes to pad, rotor and caliper design and passed the test. They won the contract as they were the only company to meet the criteria which Porsche later admitted they thought was unattainable!

The specs are 15x32mm front with a 6 piston caliper. Dual master cylinders with a balance bar. Rear brakes were 15x30 with 4 pistons but we decided to run a smaller rear set up as we donít have the rear mass. We utilized 1994 Supra turbo front rotors (12.7x1.25) with a NASCAR brembo 4 piston race caliper. The pedal assembly had the same bolt pattern as the rx7 for mounting and the same pedal ratio! We will be testing the brakes soon to set the balance and test 4 different pad compounds .




Old set up was 14 inch rotor with 4 piston monoblock brembo race caliper.
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Old 05-02-19, 08:43 PM
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Old vs new

Cut off Porsche shaft and adapted rx7 Clevis with aluminium block.

Sealed rear of front rotor and will use 5 inch ducts

Custom front spacer centres from inside to rx7 hub. Outer ring centers rotor. Other side centers wheel. Use a 3.25 arp stud !

Done. We will lighten the adapter when we have more time .


We may adapt the Porsche rotor at a later date if needed.

The rear was straightforward .
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Old 05-02-19, 09:01 PM
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We may adapt the Porsche rear rotor later. We would turn it down and have to space it out or redo the rotor hat. The front rotor was very easy as the offset was good and we just redrilled the holes to fit the rx7. We will test the pfc 08 and 11 compound in front. And the pfc 01 , mintex 06, and project Mu 21 rear.
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Old 05-03-19, 12:34 AM
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Originally Posted by racingdriver

Old vs new

Cut off Porsche shaft and adapted rx7 Clevis with aluminium block.

Sealed rear of front rotor and will use 5 inch ducts

Custom front spacer centres from inside to rx7 hub. Outer ring centers rotor. Other side centers wheel. Use a 3.25 arp stud !

Done. We will lighten the adapter when we have more time .


We may adapt the Porsche rotor at a later date if needed.

The rear was straightforward .
I recently install AP twin master cylinder in stock location. Was firewall deform compare to 991cup car also at shop , I think u should measure it's too
Attached Thumbnails Adapting Porsche 991 cup braking system for rx7-photo603.jpg  

Last edited by diyman25; 05-03-19 at 12:43 AM.
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Old 05-03-19, 10:56 AM
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Awesome project! How do the 15" rotors and calipers fit under your (I'm assuming) 18" CCWs?
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Old 05-03-19, 02:53 PM
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Here's the plate that will be used to reinforce the firewall here, 3/8" thick - offset flange masters to get better than the stock 4:1 pedal ratio. Diyman, looks like you're attempting to use the ABS going by the single lines off both front and rear masters, know a car here that tried that and the pump was a touch confused, a Bosch unit will probably work, talk about a pretty penny there!

Balance bar you have, is that 3" centres or better, certainly would have made life a lot easier here. Perhaps it's a Revolution off the shelf thing? Would be interesting to see the life of the sleeve for the balance bar after a few seasons, if it is one.
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Old 05-04-19, 01:49 AM
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Originally Posted by billyboy View Post

Here's the plate that will be used to reinforce the firewall here, 3/8" thick - offset flange masters to get better than the stock 4:1 pedal ratio. Diyman, looks like you're attempting to use the ABS going by the single lines off both front and rear masters, know a car here that tried that and the pump was a touch confused, a Bosch unit will probably work, talk about a pretty penny there!

Balance bar you have, is that 3" centres or better, certainly would have made life a lot easier here. Perhaps it's a Revolution off the shelf thing? Would be interesting to see the life of the sleeve for the balance bar after a few seasons, if it is one.
Nope I already delate ABS

Nice reinforce plate, did u use dial gauge to measure the firewall ? U will suprise the result
Attached Thumbnails Adapting Porsche 991 cup braking system for rx7-img_20190413_131503_717.jpg  
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Old 05-04-19, 04:51 PM
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I've seen the flex with the booster during brake bleeding previously, so wouldn't surprise there would be quite a bit happening like most production derived cars.

Sort of expecting double banjo at the front master rather than the T set-up, hence wondering if the ABS was in use.

Interesting clutch pedal, is that the Japanese work with the welding reinforcing the spot welds, I'd wonder what clutch they were expecting to run if so? They certainly had a bee in their bonnet with pop rivets too. The blue anodised clasp to hold the clutch reservoir, was that made or purchased....was thinking of using a couple of large P clips there?

Brake pedal must be pretty firm with 3/4" masters too.
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Old 05-06-19, 08:02 AM
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Amazing setup, I'd love to duplicate this but it might be a bit overkill for my weekend track car.

How is the brake pedal feel on the new setup compared to the factory booster setup?
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Old 05-13-19, 12:05 AM
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wow !

Is that the Porsche booster and MC?
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