225/40R18 vs 265/35R18
Switching from 225/40R18 to 265/35R18 increases the overall diameter by 5.5 mm (0.9%). That is within the usual ±3% guideline.
| 225/40R18 | 265/35R18 | Difference (mm / revs) | |
|---|---|---|---|
| Section width | 225 mm | 265 mm | +40.0 |
| Sidewall height | 90.0 mm | 92.8 mm | +2.8 |
| Rim diameter | 457.2 mm | 457.2 mm | +0.0 |
| Overall diameter | 637.2 mm | 642.7 mm | +5.5 |
| Circumference | 2,001.8 mm | 2,019.1 mm | +17.3 |
| Revolutions | 500 per km | 495 per km | -5.0 |
Speedometer effect
With 265/35R18 fitted on a car calibrated for 225/40R18, the real speed when the speedometer shows:
| Speedometer shows | Actual speed |
|---|---|
| 50 km/h | 50.4 km/h |
| 80 km/h | 80.7 km/h |
| 100 km/h | 100.9 km/h |
| 120 km/h | 121.0 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 265 mm tire has a manufacturer-specified rim width range.
225/40R18 dimensions · 265/35R18 dimensions · Open in calculator