255/70R16 vs 265/50R20
Switching from 255/70R16 to 265/50R20 increases the overall diameter by 9.6 mm (1.3%). That is within the usual ±3% guideline.
| 255/70R16 | 265/50R20 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 255 mm | 265 mm | +10.0 |
| Sidewall height | 178.5 mm | 132.5 mm | -46.0 |
| Rim diameter | 406.4 mm | 508.0 mm | +101.6 |
| Overall diameter | 763.4 mm | 773.0 mm | +9.6 |
| Circumference | 2,398.3 mm | 2,428.5 mm | +30.2 |
| Revolutions | 417 per km | 412 per km | -5.0 |
Speedometer effect
With 265/50R20 fitted on a car calibrated for 255/70R16, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 50.6 km/h |
| 80 km/h | 81.0 km/h |
| 100 km/h | 101.3 km/h |
| 120 km/h | 121.5 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.
255/70R16 dimensions · 265/50R20 dimensions · Open in calculator