265/70R18 vs 275/60R20
Switching from 265/70R18 to 275/60R20 increases the overall diameter by 9.8 mm (1.2%). That is within the usual ±3% guideline.
| 265/70R18 | 275/60R20 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 265 mm | 275 mm | +10.0 |
| Sidewall height | 185.5 mm | 165.0 mm | -20.5 |
| Rim diameter | 457.2 mm | 508.0 mm | +50.8 |
| Overall diameter | 828.2 mm | 838.0 mm | +9.8 |
| Circumference | 2,601.9 mm | 2,632.7 mm | +30.8 |
| Revolutions | 384 per km | 380 per km | -4.0 |
Speedometer effect
With 275/60R20 fitted on a car calibrated for 265/70R18, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 50.6 km/h |
| 80 km/h | 80.9 km/h |
| 100 km/h | 101.2 km/h |
| 120 km/h | 121.4 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 275 mm tire has a manufacturer-specified rim width range.
265/70R18 dimensions · 275/60R20 dimensions · Open in calculator