255/70R18 vs 265/70R18
Switching from 255/70R18 to 265/70R18 increases the overall diameter by 14.0 mm (1.7%). That is within the usual ±3% guideline.
| 255/70R18 | 265/70R18 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 255 mm | 265 mm | +10.0 |
| Sidewall height | 178.5 mm | 185.5 mm | +7.0 |
| Rim diameter | 457.2 mm | 457.2 mm | +0.0 |
| Overall diameter | 814.2 mm | 828.2 mm | +14.0 |
| Circumference | 2,557.9 mm | 2,601.9 mm | +44.0 |
| Revolutions | 391 per km | 384 per km | -7.0 |
Speedometer effect
With 265/70R18 fitted on a car calibrated for 255/70R18, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 50.9 km/h |
| 80 km/h | 81.4 km/h |
| 100 km/h | 101.7 km/h |
| 120 km/h | 122.1 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 265 mm tire has a manufacturer-specified rim width range.
255/70R18 dimensions · 265/70R18 dimensions · Open in calculator