Speedometer Calibration - How Does it work

[ege...@gmail.com]

The Actual speed is 90 and the calibration reading is 94. Does this
mean my speedometer was showing 90 MPH when the actual was 94 MPH? Is
the speedometer faulty?

Thanks,
Nauman.

[larry_s...@yahoo.com]

>From the day you bought your car, things have changed. Your tires
have less tread than they did on day one. If you have replaced the
original tires, the new tires might be a different size than the
originals. Even if they are the same listed size, if they are a
different model (perhaps from a different tire manufacturer), they
could be physically larger or smaller than the original ones were
originally.

The speedometer and odometer do not measure the actual distance you
travel; they estimate it based on the original equipment tire size.

As to your question of Faulty? Not hardly. Mis-calibrated? Perhaps,
but certainly not faulty.

Whether you want to spend good money to have it re-calibrated is up to
you; most of us who care have our car's odometer/speedometer measured
periodically and learn how to adjust. In Southern California, AAA
provides a free odometer/speedometer check. Check with your local
auto club.

Your mileage may vary.