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I have got the standard GTI trackerjack kit for my car, which I can see I am going to have to upgrade at some point. It's a Nissan CA18DET going into it with a hybrid T25 turbo, so it should be about 230 BHP. My plan is to get the car up and running with this brake set up, then upgrade the brakes/wheels/tyres later on.
Does anyone know if the larger Passat discs are a big improvement over the GTI ones?
The point of bigger dia discs (as Graham will tell you) is to move the piston centres outboard. My mod only moves these centres an extra 8.5mm further out which doesn't seem like a lot, but the effects are not linear, they are exponential. I haven't worked it out exactly, but it's about the same again as going from stock to TJs. So I expect a decent return for my investment. As it's only travelled a few hundred yards under it's own power so far (making sure the ecu controlled trans shifts properly) I can't yet say exactly HOW much better. But as Graham says and I agree, you CAN make the brakes TOO good! I'd try the car with the normal 239mm discs first and see how you get on with it. Car weight is also a factor, are you running it fully trimmed or as a stripped out racer? The Carledo is down to a kerb weight of 760kg (+82kg of ME) to make the most of it's miserable 140odd horses, but the standard 239mm TJs are fine with that, no fade at all and consistent stopping, from a ton or a bit more, for a full days track use at Castle Coombe. The MOT brake testing weight (including driver, spare wheel, tools, half a tank of gas and "accumulated road dirt" for a standard, fully trimmed Sprint is something like 1270kg IIRC. That's a big difference!
To Dave, the Puma calipers are the same 54mm dia pistons as the Sierra ones on the original TJ design (standard Sprint is 48mm) It's moving them outboard that makes the difference (see above) Keeping the same size piston is important to avoid the "long pedal" induced by increasing piston size, the 54s are enough! Any bigger and you'd need to find a bigger bore master cylinder to compensate.
Incidentally, whilst researching the calipers I wanted to use, I discovered that many of them are pretty much identical and interchangeable, it's the caliper carriers that vary from model to model and by disc dia and sometimes pad shape. One of the reasons I picked the Puma ones (apart from the fact that I HAD some) is that they run a larger area pad than most of the similar Ka, Fiesta, Sierra and Escort models. In braking efficiency terms that's no real advantage, but bigger pads will run a tad cooler and last longer in service (OK, i'm tight, sue me) I see it as a positive with my pad hungry automatic car.
Steve