175/65R15 vs 175/70R14
Switching from 175/65R15 to 175/70R14 decreases the overall diameter by 7.9 mm (1.3%). That is within the usual ±3% guideline.
| 175/65R15 | 175/70R14 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 175 mm | 175 mm | +0.0 |
| Sidewall height | 113.8 mm | 122.5 mm | +8.7 |
| Rim diameter | 381.0 mm | 355.6 mm | -25.4 |
| Overall diameter | 608.5 mm | 600.6 mm | -7.9 |
| Circumference | 1,911.7 mm | 1,886.8 mm | -24.9 |
| Revolutions | 523 per km | 530 per km | +7.0 |
Speedometer effect
With 175/70R14 fitted on a car calibrated for 175/65R15, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 49.4 km/h |
| 80 km/h | 79.0 km/h |
| 100 km/h | 98.7 km/h |
| 120 km/h | 118.4 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 175 mm tire has a manufacturer-specified rim width range.
175/65R15 dimensions · 175/70R14 dimensions · Open in calculator