225/55R18 vs 235/65R16
Switching from 225/55R18 to 235/65R16 increases the overall diameter by 7.2 mm (1.0%). That is within the usual ±3% guideline.
| 225/55R18 | 235/65R16 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 225 mm | 235 mm | +10.0 |
| Sidewall height | 123.8 mm | 152.8 mm | +29.0 |
| Rim diameter | 457.2 mm | 406.4 mm | -50.8 |
| Overall diameter | 704.7 mm | 711.9 mm | +7.2 |
| Circumference | 2,213.9 mm | 2,236.5 mm | +22.6 |
| Revolutions | 452 per km | 447 per km | -5.0 |
Speedometer effect
With 235/65R16 fitted on a car calibrated for 225/55R18, 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 235 mm tire has a manufacturer-specified rim width range.
225/55R18 dimensions · 235/65R16 dimensions · Open in calculator