245/50R20 vs 245/65R17
Switching from 245/50R20 to 245/65R17 decreases the overall diameter by 2.7 mm (0.4%). That is within the usual ±3% guideline.
| 245/50R20 | 245/65R17 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 245 mm | 245 mm | +0.0 |
| Sidewall height | 122.5 mm | 159.2 mm | +36.7 |
| Rim diameter | 508.0 mm | 431.8 mm | -76.2 |
| Overall diameter | 753.0 mm | 750.3 mm | -2.7 |
| Circumference | 2,365.6 mm | 2,357.1 mm | -8.5 |
| Revolutions | 423 per km | 424 per km | +1.0 |
Speedometer effect
With 245/65R17 fitted on a car calibrated for 245/50R20, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 49.8 km/h |
| 80 km/h | 79.7 km/h |
| 100 km/h | 99.6 km/h |
| 120 km/h | 119.6 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 245 mm tire has a manufacturer-specified rim width range.
245/50R20 dimensions · 245/65R17 dimensions · Open in calculator