Speedo Correction for Larger Tires

[louis.robins]

I always use the GPS when I travel.

[1der]

I use GPS for speed validation and also to confirm odometer readings.

Typically at fill up I zero out the trip meter on the Speedo and zero out the GPS distance/trip meter. After 100 or so miles (or more) I compare the two. This gives me the error correction % for calculating true distance traveled for accurate mpg calcs.