BMW Motorsport Group A 6 Piston (titanium) calipers - SOLD
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For sale is a pair of AP Racing CP3555 6 piston (titanium) calipers, same as what is specified in the BMW Motorsport Group A catalogue, and was used in the early 90's by the E30 M3 DTM race cars, Mercedes Benz 190E DTM race cars, and the BMW E36 STW race cars. These were the calipers that won the E30 M3 the 1987 championship in the Australian Touring Car Championship as the brake pads would last forever (avoiding the need for a pad change) giving the E30 M3 an unfair advantage against competitors such as the Skyline R32 GTR, Ford Sierra RS500, and in the following years, the championship enforced a compulsory pad change to level the competition, and the championship was then dominated by Ford and Nissan.
Pads (shape CP3558 D54) are the same as what's used in the current AP Racing CP9668 caliper, so heaps of different pads are available. They are 25mm thick options and 18mm options, with heaps of long lasting endurance pads available (this is a caliper specifically designed for endurance racing). I can supply an old set of Pagid RS19's if wanted (approx 20mm thick).
To put 25mm thick pads into perspective, stock m3 pads are 20mm thick, and Porsche street gt3 cars are 16mm thick. 991 GT3 cup cars are 28mm thick.
I have weighed, calulated and confirmed the pistons to be titanium, gold coating is titanium nitride. Each piston is supported by anti-knock-back springs. Seals (hydraulic and dust) are in good condition, but I suggest installing new ones along with new nipples and cross tubes.
I think the rotors compatible are 343mm and 355mm. Any machine shop these days can easily and affordably make hats and brackets to suit. There's a photo on the web showing a CP9668 (newer model of this caliper fitting under a 17in apex arc-8 wheel.
I'm selling as I've decided to stick with an OEM wheel, thus won't fit this caliper. DTM cars ran 18in wheels.
Only issue I need to inform buyers is that, these are 2x right calipers. Being a modular design, they are structually symmetrical, hence can be physically installed on the left or right with nipples/tubes also can be adjusted to suit either side (photos currently show them setup for Left/Right configuration). Only issue is the piston sizing. Left caliper will have the larger piston leading, but the right side will have the small piston leading. I'm not sure what the affect this will have on pad taper wear, but it's pretty easy to remove pads, just the top bridge needs to be removed and pads can be swapped around if there they're not wearing evenly. This is not going to be an issue for track days and long mountain drives, but for 24hr ensurance racing, I'd suggest the current production CP9668 caliper (but you'll get stainless steel pistons instead of these titanium ones :P)
Previous model of these 6 piston calipers were advised here for €3600, and are now sold, so these pieces of motorsport history are quickly becoming unobtainable for anyone wanting to build a period correct DTM/STW car, hence asking for £2000 or equivalent in any other currency over paypal.
A few more photos are available.