175/65R15 vs 215/40R17
Switching from 175/65R15 to 215/40R17 decreases the overall diameter by 4.7 mm (0.8%). That is within the usual ±3% guideline.
| 175/65R15 | 215/40R17 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 175 mm | 215 mm | +40.0 |
| Sidewall height | 113.8 mm | 86.0 mm | -27.8 |
| Rim diameter | 381.0 mm | 431.8 mm | +50.8 |
| Overall diameter | 608.5 mm | 603.8 mm | -4.7 |
| Circumference | 1,911.7 mm | 1,896.9 mm | -14.8 |
| Revolutions | 523 per km | 527 per km | +4.0 |
Speedometer effect
With 215/40R17 fitted on a car calibrated for 175/65R15, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 49.6 km/h |
| 80 km/h | 79.4 km/h |
| 100 km/h | 99.2 km/h |
| 120 km/h | 119.1 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 215 mm tire has a manufacturer-specified rim width range.
175/65R15 dimensions · 215/40R17 dimensions · Open in calculator