Quick question: Does anyone know which wheel(s) are used to track the speedometer/odometer readings?

I'm trying to determine which wheels need to remain as close as possible to factory circumference when upgrading wheel & tires.

 

I have 20's.....my Speedo is off 3mph so when the odometer says 60 im going 63. Larger diameter also means less miles then it really says.

 

I think the speed is measured from the ABS sensors, and, most changes don't effect the speedo readings very much, if at all. How would the car compensate for 19s in the rear and 18s in the front? I dunno. But when I had that setup, I don't think there was any difference in the speedo settings.

Try a Search too - we've discussed this before

 

i have 20's and drove by one of those cop speed tellers recently and was only off by 1 mph but i heard that those thing r wrong anyway.