Quote:
Originally Posted by calintexas
I don't know where BMW is picking up the speedometer signal.
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All modern cars get it from the tranny; that's why changing tire diameter increases or decreases speedometer error. I'm not sure how the ECU interprets wheel speed sensor input for DSC/TC purposes, but it only needs relative differences.. along with input from the yaw sensor, obviously.
As far as odometer accuracy, most cars are pretty accurate. But for some weird reason, most cars are WAY more optimistic with the speedometer than they need to be to cover their butts for understating speed lawsuits. I've used 3 different cars to the same destination, and all 3 recorded between 400.0 and 400.1 miles. And yes, the worst speedo error was the M3, according to the same police radar unit entering one of the towns, so apples with apples.