155/80R13 vs 175/70R13
Switching from 155/80R13 to 175/70R13 decreases the overall diameter by 3.0 mm (0.5%). That is within the usual ±3% guideline.
| 155/80R13 | 175/70R13 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 155 mm | 175 mm | +20.0 |
| Sidewall height | 124.0 mm | 122.5 mm | -1.5 |
| Rim diameter | 330.2 mm | 330.2 mm | +0.0 |
| Overall diameter | 578.2 mm | 575.2 mm | -3.0 |
| Circumference | 1,816.5 mm | 1,807.0 mm | -9.5 |
| Revolutions | 551 per km | 553 per km | +2.0 |
Speedometer effect
With 175/70R13 fitted on a car calibrated for 155/80R13, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 49.7 km/h |
| 80 km/h | 79.6 km/h |
| 100 km/h | 99.5 km/h |
| 120 km/h | 119.4 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.
155/80R13 dimensions · 175/70R13 dimensions · Open in calculator