255/70R18 vs 285/45R22
Switching from 255/70R18 to 285/45R22 increases the overall diameter by 1.1 mm (0.1%). That is within the usual ±3% guideline.
| 255/70R18 | 285/45R22 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 255 mm | 285 mm | +30.0 |
| Sidewall height | 178.5 mm | 128.2 mm | -50.3 |
| Rim diameter | 457.2 mm | 558.8 mm | +101.6 |
| Overall diameter | 814.2 mm | 815.3 mm | +1.1 |
| Circumference | 2,557.9 mm | 2,561.3 mm | +3.4 |
| Revolutions | 391 per km | 390 per km | -1.0 |
Speedometer effect
With 285/45R22 fitted on a car calibrated for 255/70R18, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 50.1 km/h |
| 80 km/h | 80.1 km/h |
| 100 km/h | 100.1 km/h |
| 120 km/h | 120.2 km/h |
Larger tires make the car go faster than the speedometer shows. Most speedometers also read slightly high from the factory.
Before you change size
- Check the sizes approved for your vehicle on the door-jamb placard or in the owner's manual.
- Check clearance to suspension, brakes and arches at full lock and full compression.
- Match or exceed the original load index and speed rating.
- Wider tires need an appropriate rim width; a 285 mm tire has a manufacturer-specified rim width range.
255/70R18 dimensions · 285/45R22 dimensions · Open in calculator