235/60R18 vs 245/65R17
Switching from 235/60R18 to 245/65R17 increases the overall diameter by 11.1 mm (1.5%). That is within the usual ±3% guideline.
| 235/60R18 | 245/65R17 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 235 mm | 245 mm | +10.0 |
| Sidewall height | 141.0 mm | 159.2 mm | +18.2 |
| Rim diameter | 457.2 mm | 431.8 mm | -25.4 |
| Overall diameter | 739.2 mm | 750.3 mm | +11.1 |
| Circumference | 2,322.3 mm | 2,357.1 mm | +34.8 |
| Revolutions | 431 per km | 424 per km | -7.0 |
Speedometer effect
With 245/65R17 fitted on a car calibrated for 235/60R18, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 50.8 km/h |
| 80 km/h | 81.2 km/h |
| 100 km/h | 101.5 km/h |
| 120 km/h | 121.8 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 245 mm tire has a manufacturer-specified rim width range.
235/60R18 dimensions · 245/65R17 dimensions · Open in calculator