175/65R15 vs 185/70R14
Switching from 175/65R15 to 185/70R14 increases the overall diameter by 6.1 mm (1.0%). That is within the usual ±3% guideline.
| 175/65R15 | 185/70R14 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 175 mm | 185 mm | +10.0 |
| Sidewall height | 113.8 mm | 129.5 mm | +15.7 |
| Rim diameter | 381.0 mm | 355.6 mm | -25.4 |
| Overall diameter | 608.5 mm | 614.6 mm | +6.1 |
| Circumference | 1,911.7 mm | 1,930.8 mm | +19.1 |
| Revolutions | 523 per km | 518 per km | -5.0 |
Speedometer effect
With 185/70R14 fitted on a car calibrated for 175/65R15, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 50.5 km/h |
| 80 km/h | 80.8 km/h |
| 100 km/h | 101.0 km/h |
| 120 km/h | 121.2 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 185 mm tire has a manufacturer-specified rim width range.
175/65R15 dimensions · 185/70R14 dimensions · Open in calculator