Just as a point of fact, I checked my speedo with 2 separate township's stationary radar and timing the measured mile on the highway. With a 29.5" diameter tire, my speedo reads 2 or 3 mph HIGHER than the radars and spot on with the measured mile, that's 60 seconds at 60 mph. It's hard to drive only 60 with traffic flying by! I could have done it at 70, but the math would be intense! LOL! That would be 51.43 sec/mile.