Pete_Rockett

For a reasonably quick way to do it, use a GPS to find your actual speed and then take the ratio of that to what the speedometer says; i.e., if the speedo says 70 and the GPS says 60, divide 60 by 70 = .85. Subtract that from 1 = .15. Add one to that and multiply by what you think the stock ratio is (3.31 *1.15 = 3.59) That is your gear ratio. Of course there is no 3.59 - this is just an example.