185/70R14 vs 205/45R17
Switching from 185/70R14 to 205/45R17 increases the overall diameter by 1.7 mm (0.3%). That is within the usual ±3% guideline.
| 185/70R14 | 205/45R17 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 185 mm | 205 mm | +20.0 |
| Sidewall height | 129.5 mm | 92.2 mm | -37.3 |
| Rim diameter | 355.6 mm | 431.8 mm | +76.2 |
| Overall diameter | 614.6 mm | 616.3 mm | +1.7 |
| Circumference | 1,930.8 mm | 1,936.2 mm | +5.4 |
| Revolutions | 518 per km | 516 per km | -2.0 |
Speedometer effect
With 205/45R17 fitted on a car calibrated for 185/70R14, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 50.1 km/h |
| 80 km/h | 80.2 km/h |
| 100 km/h | 100.3 km/h |
| 120 km/h | 120.3 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 205 mm tire has a manufacturer-specified rim width range.
185/70R14 dimensions · 205/45R17 dimensions · Open in calculator