Agreed on Jamie's analysis of approaching improving the brakes. Technique is a big problem for a lot of people. Driving on the street creates bad habits that translate to the track and it takes awhile to learn to unlearn the street braking.
Cooling is something the brakes do indeed lack. The Fuchs are great wheels but do not do much to help cooling. Removal of the splash shields helps get the rotors better exposed to the air. Ducts are a great approach but the routing of the hoses is often not very straight and that kills the velocity of the air. Ducts also like to have suitable backing plates with a hose spigot in the plate to direct the cooling air into the rotor eye.
A suitable alternative to ducting is scoops like the 993 has in the front. They work quite well and are cheap & easy to install with a drill and some zip ties. Do a search- i've participated in a few of the scoop discussions.
Stock brakes are quite capable but their shortcoming is the seals and the iron caliper body is a good heat sink (and not as good at releasing the heat). The Ate or FTE brand seals for these calipers are not very heat tolerant. Hence the point that getting the brakes cooled is important since you're attacking the problem at the source along with using the necessary retardants (higher temperature fluid, race pads) to combat the heat.
Carrera brakes are good but they're still wanting a bit more in really hard use. They still require periodic caliper rebuilds (pressure seals eventually leak -dangerous- and the dust boots turn to dust- both indicative of considerably high brake temps) and rather frequent pad & rotor replacement.
I'm not saying upsized expensive brakes are an absolute must. The stock brakes can be managed well, perform well and are very durable for years and years. But the upsize in brakes does come with notably improved performance. Pads and rotors last much much longer, caliper seals don't fail, brake fluid bleeding before each track event is no longer an absolute must (but certainly a good practice especially if you ever feel the pedal getting soft)
The list for the 930 setup that Jamie provided is spot-on. But it can be enhanced a little bit IMO.
Quote:
The 930 brakes will need 4X calipers, Early (78-79) front rotor hats, Early front rotors (non-offset), rear 930 rotors, 23mm Master Cylinder, modified actuator pin (not sure on vacuum boost cars), new hard lines at strut and trailing arms.
Front installation is bolt-on. Rear requires trimming brake dust cover mount trimming.
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930 front calipers are great and bolt right on the SC strut with the factory 3.5mm spacing washers. You do need to install a longer hard brake line and the original 930 line is direct fit. Or you can bend your own.
The rotor does not have to be the 78-79 floating style. A few examples of alternative rotors are the really nice Wilwood GT (i'm disappointed Wilwood appears to be discontinuing the HD line) or the fantastic AP racing 60 vane rotor. The AP disc is kickass disc and a great value at $165 each. I'll be giving those a try at my next rotor replacement.
Wilwood High-Performance Disc Brakes - Rotor No: 160-11837
Essex - AP Racing J Hook
Both the above rotors use a common 8 x 7.00" hat circle and that allows use of Rebel's very nice 8 bolt mounting hats. (1/2 way down the page)
brake system components Rebel S Racing Products
This bolted/fixed rotor & hat combo is a much cheaper and very good alternative to the factory floating $etup. But if you really feel like you want floaters for best performance in heavy duty environment, floating is indeed the better the way to go. OEM Zimmerman, Sebro rotors are excellent and Brembo also makes a copy of this rotor. However, $350 per rotor is NOT cheap
1979 Porsche 930 Turbo Coupe - Brake Pads & Rotors - Page 2
To make the OEM floating rotors work, you can use the Rebel 12 bolt hats in the above link and use Coleman Racing T-locks with the hardware of your choice. Beware, these truly floating rotors are freakin' noisy once they loosen up & are cold
T-Lock, Floating Rotor Mount
Jamie is indeed correct that the 930 calipers require the 23.8mm 930 master cylinder. On vacuum boosted cars, the '78-'89 930 master cylinder is a direct bolt in no modifications necessary installation.
The rear 930 calipers are not a must. You can cut costs there by using a more common small Brembo rear caliper from the 964, 993, 928, 944T, etc. The 28/30 piston sizing of the 964/944T/968/928 is a cheap alternative to the 30/30 sized 930 caliper in terms of cost to buy and adapting to the 911 rear axle. Use of these calipers with the 930 fronts gives you 964-like hydraulic bias which is pretty decent. However these calipers need to be widened inside to allow the 930 rotor to fit.
It's not that hard
993 Caliper Mods- Grinding and Drilling
Actually the 993 or 964T rear caliper with its larger 30/34 pistons is a great choice for the hydraulic bias it creates. Its a bit aggressive in the neighborhood of 993RS type bias. So a well set up car with limited slip diff would be important to tame the more aggressive rear brake bias. 964T caliper is the best choice because it's already the proper internal width for the 930 309x28mm rotor and doesn't require widening. Routing the fluid feed line to these common Brembos is also easier than the 930 caliper. Simply re-bend the existing line from your SC caliper.
So as you can see, you can go pure 930 front and rear but it's pretty expensive. Like Jamie said, do you really need this. Or you can change things up a bit and mix & match things to create a Frankenstein 930-like combo. Frankenstein 930 brake setup is not bargain basement cheaper but it is a considerable savings over pure 930. The cost savings in calipers alone is $800 on average (used 930 rears are typically $1000 whereas you can get common Brembo rears all day long off eBay for ~$200 or ~$400 for the 993 or 964T) and you also save a bit more in the simpler adapting of the common Brembos. You can DIY the adapting of the common Brembos if you have a drill press and some patience. Or give it to a machinist and they'll knock it out for a decent price. The 930 adapting should be undertaken by a machinist for sure.