185/65R15 vs 185/70R14
Switching from 185/65R15 to 185/70R14 decreases the overall diameter by 6.9 mm (1.1%). That is within the usual ±3% guideline.
| 185/65R15 | 185/70R14 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 185 mm | 185 mm | +0.0 |
| Sidewall height | 120.2 mm | 129.5 mm | +9.3 |
| Rim diameter | 381.0 mm | 355.6 mm | -25.4 |
| Overall diameter | 621.5 mm | 614.6 mm | -6.9 |
| Circumference | 1,952.5 mm | 1,930.8 mm | -21.7 |
| Revolutions | 512 per km | 518 per km | +6.0 |
Speedometer effect
With 185/70R14 fitted on a car calibrated for 185/65R15, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 49.4 km/h |
| 80 km/h | 79.1 km/h |
| 100 km/h | 98.9 km/h |
| 120 km/h | 118.7 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 185 mm tire has a manufacturer-specified rim width range.
185/65R15 dimensions · 185/70R14 dimensions · Open in calculator