Quote:
Originally Posted by SmartBastard
Never go larger diameter on your wheels than stock. This will screw up your ABS and therefor your breaking distance will be longer.
As far as I was told, with bigger diameter your wheels turn less times than they should, which under braking can mean that ABS will "think" that your wheels are sliding and therefor will lower the pressure from the break pads. I was urged by people who do racing to never put bigger diameter wheels on BMW.
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You should keep the rolling diameter (a function of the tire and wheel) close to stock, but some deviation is not only unavoidable, but innate in the fact that the tire itself wears. Going + or - while changing the tire size to compensate keeping rolling diameter close is not a problem, and BMW themselves offer numerous tire/wheel packages and sizes from the factory and as dealer accessories. They don't change abs sensors with different wheels/tires.
As I understand it, the abs sensors work relative to one another, and are not so sensitive that a slight percentage difference in rolling diameter will make a difference. I've had many different sizes on my car, and anecdotally haven't noticed major differences in stopping or ABS threshold I couldn't attribute to the tire I was running, rather than it's size, or the alignment I was running.
Back on topic...I run 235/265 RE-11s in the summer, and I like the tires alot but aside from being expensive, if I were to buy them again I would try a 245/275 set up. This really seems to be a car you would want to cram as much tire as you can under it, with tendencies to understeer in / oversteer out. I don't believe that 245/275 street tires will completely solve this, but more mechanical grip can't hurt. If they are in stock when the time comes I'll likely end up on R-S3s.