255/65R18 vs 265/70R16
Switching from 255/65R18 to 265/70R16 decreases the overall diameter by 11.3 mm (1.4%). That is within the usual ±3% guideline.
| 255/65R18 | 265/70R16 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 255 mm | 265 mm | +10.0 |
| Sidewall height | 165.8 mm | 185.5 mm | +19.7 |
| Rim diameter | 457.2 mm | 406.4 mm | -50.8 |
| Overall diameter | 788.7 mm | 777.4 mm | -11.3 |
| Circumference | 2,477.8 mm | 2,442.3 mm | -35.5 |
| Revolutions | 404 per km | 409 per km | +5.0 |
Speedometer effect
With 265/70R16 fitted on a car calibrated for 255/65R18, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 49.3 km/h |
| 80 km/h | 78.9 km/h |
| 100 km/h | 98.6 km/h |
| 120 km/h | 118.3 km/h |
Smaller tires make the speedometer read higher than the actual speed. 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.
255/65R18 dimensions · 265/70R16 dimensions · Open in calculator