Adrian

Methinks you should go back and look at the 1990 to 1994 race series that permitted the Carrera Cups to enter in various versions but all were Carrera Cups. You should also check the current cup series and where the cups that are used come from.
However we are now digressing. A Carrera Cup is not just a Cup exactly the same as a C4 is not just a C4 or a C2 is not just a C2. There are many versions and variants and each modification must be dealt with on each individual 964 based on its current modification status. A huge amount of money is wasted/lost when people purchase things that do not fit or require extensive modifications to fit.
Ciao,
Adrian
964C4

Cupcar

My information is that the Carrera Cup series cars were allowed switchable ABS so it was up to the driver whether or not the ABS was on. This is because some drivers don't like the feel of the system and ABS can be a liability if the car is spinning backward.

The European RS wiring harness has built in connections to switch the ABS these are illustrated in the 964 shop manual on page 97-121: "911 Carrera 2 Model 92 Sheet 4B ABS Turbo Look". Look in fields J 37 & 38 where is says "only RS".

The American Cup series did not have the luxury of a built in connection so Porsche made a special harness part number 964.612.003.75 to incorporate the connections into the standard American harness. My car has one of these installed.

The Carrera Cups had 2 switches in the system one on the dash and another in the hydraulic lines that allowed the system to be turned off with a big stomp on the pedal if the car is in a spin.

Some of the teams may have elected to remove the ABS brain entirely and not deal with any of the switching if the driver didn't want it.

The Carrera Cups used the European RS braking system as described by Bill Verburg: 44/36 front calipers on 322x32 discs & small 34/30 rear calipers on 299x24 discs w. a hyd boosted 25.4mm m/c.

The only modifications to the Euro RS system besides the deletable ABS for the Carrera Cup cars was:

1. Backing plate removal
2. Heat shielding installed for the ABS wiring (since it was now necessary with the backing plates removed).
3. Pagid brake pads
4. Proportioning valve removal

The proportioning valve was removed to allow greater brake line pressure and greater braking by the rear wheels. This works with the Carrera Cup cars since they are 55 mm lower than a standard European car- 65 mm lower than an American car. The lower the center of gravity, the less weight shifted to the front of the car and the more you can use the rear brakes. Also the drivers in the racing cars are presumably better than average and can handle a car with more rear brake bias, something that makes the car more twitchy under braking and harder to control.

Adrian is right I feel, unless the car is used at the track and the brakes are fading you don't need bigger brakes, the standard 964 brakes are great if in good shape. Adding rotating unsprung mass is not what the car needs.

If you want to read a good study go to this site:Nissan Brake Test

Note that the Nissan 350Z stops essentially no better with the optional Brembo brakes, it can just stop more times as the system runs cooler. Also note adding bigger brakes does no good for stopping distances either. Also note that at the end of the day adding huge brakes really screwed things up. It takes a lot of homework to do it right.