Calculator for the right gear ratio on the speedometer.
To determine the correct gear ratio of the speedometer for your car, use the following formula to calculate the number of teeth on the driven gear (round to the nearest available gear):
Use the following formula to calculate "tire revolutions per mile" for the formula above:
With 15 Tooth Drive Gear
Axle Ratio | Tire Height | Driven Gear Teeth |
---|---|---|
4.56 | 33 | 42 |
4.56 | 35 | 39 |
4.10 | 26 | 45 will work, but will read about 3 MPH fast at 50 MPH. |
4.10 | 27 | 45 |
4.10 | 28 | 44 |
4.10 | 29 | 43 |
4.10 | 30 | 41 |
4.10 | 31 | 40 |
4.10 | 33 | 38 |
4.10 | 35 | 35 |
3.73 | 26 | 43 |
3.73 | 27 | 42 |
3.73 | 27 1/2 | 41 |
3.73 | 28 | 40 |
3.73 | 29 | 39 |
3.73 | 30 | 38 |
3.73 | 31 | 36 |
With 17 Tooth Drive Gear
Axle Ratio | Tire Height | Driven Gear Teeth |
---|---|---|
3.73 | 28 | 45 |
3.73 | 29 | 44 |
3.42 | 26 | 45 |
3.42 | 26 1/2 | 44 |
3.42 | 27 | 43 |
3.42 | 28 | 42 |
With 18 Tooth Drive Gear
Axle Ratio | Tire Height | Driven Gear Teeth |
---|---|---|
3.23 | 26 | 45 |
3.23 | 26 1/2 | 44 |
3.23 | 27 | 43 |
3.23 | 28 | 42 |