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Old 05-03-2003, 04:18 PM
Senior Member
Join Date: Sep 2002
Posts: 2,486
Hi rrf, interesting question. Your correct to assume that the traction system "doesn't care" about acceptable differences in tire diameter. This is why you can get away with having two new tires and two old tires on the car at the same time. As far as version coding goes, tire information isn't needed. You must remember how ESP works. Lateral/longitudinal acceleration, steering angle, wheel speed, etc, are taken into account to determine if any intervention is needed. ABS only looks at wheel speed. ESP is used to slow a spinning wheel ( by selective braking ) to prevent the vehicle from getting "out of shape". The spinning wheel doesn't necessarily mean it's lost traction though. That would be a function of ASR. ABS is used to prevent a wheel from locking up by reducing/regulating braking pressure. As far as ABS being "too eager" to activate, this is a function of the ECU looking at wheel speed, so the actual tire size doesn't come into play. Lastly, BAS is something altogether different and deserves it's own Shop Forum Topic!
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