[El Diablo]

Ryan,
Doesn't the speedo based its measurement off the wheels/tires so the size of tires will affect it. But with a different diff ratio your rpm's would just be higher for the same speed and therefore should not affect the speedo reading. Typical error between speedo reading and actual could be 3% easily according to BMW.
-Roberto

 

[mfizzlenyc]

use a gps unit and see how much you off ...

 

[mikeoski]

The gearing will increase the rpms of your engine by about 500. I don't believe it will affect the speedometer. So when in 6th and cruising at 80 mph my tac would normally read 2500 rpms. Now with the 3.45:1 diff, I am reading 3000 rpms. Hope this helps.

Mike

 

[gsfent]

The gearing will increase the rpms of your engine by about 500. I don't believe it will affect the speedometer. So when in 6th and cruising at 80 mph my tac would normally read 2500 rpms. Now with the 3.45:1 diff, I am reading 3000 rpms. Hope this helps.

Mike

+1.
Regards,
Jerry