Speedometer Read High
 

I've thought this for a while, but now I have proof. When following my wife on the interstate, she was going 65. My speedo said 70 mph.

I'm not sure if this problem is electrical or mechanical in nature.

Rammstein, did you have this problem? Do you know if this car has an S2 differential? (Would that even cause a high speed reading?)

If this is electrical in nature, how to diagnose?

tires will do it too - even just 50% life on a tire wil change things by about a mile an hour - differnet brands have different physical measurements, even though the size says the same - take a look at tire rack - they have specs on the tires

that being said, the 968 is way off - there was an article done a number of years ago that said just how bad - at 130 it was about 10 high - it wouldn't surprise me that others are off too

yep - check the size of your wheels and tires.. if they, combined, have a smaller OD than stock, then they'll make your speedo read high.