Speedo Fix

  • Sponsors (?)

Doing it legit in your garage, since this is not as simple as plugging numbers in, as diameter changes all the time.

Dab of grease on centre tread, roll car til the grease hits twice, measure the distance between centre of the spots in inches. Convert a mile into inches, (63, 360)

Divide 63360/your distance measure = RPM of your actual tire, as close as you'll get it.