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      07-30-2011, 11:21 AM   #1
LarThaL
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Drives: 2011 M3
Join Date: Apr 2011
Location: West Springfield, MA

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Does the speedometer calculate speed off the front wheels or the rear?

Basically, I'm trying to figure out which tire diameter is crucial to keep speedometer readings accurate.

Also, how much can you change the relative tire diameters from stock before it messes up the stability functions, brake anti-lock, etc.

The stock rear is 668mm and the stock front is 654mm. 14mm or 2.5% difference.
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2014 Audi S6 * 2015 Audi S3 * 2015 Porsche Cayman GTS
Former 2011 BMW M3 owner