225/55R18 vs 255/55R18
255/55R18 is outside the ±3% rule as a replacement for 225/55R18: the diameter differs by +4.68%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/55R18 on a car calibrated for 225/55R18, the speedometer reads 57.3 mph when you're really doing 60, and the odometer under-counts by 4.7%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.4 mph |
| 45 mph | 47.1 mph |
| 60 mph | 62.8 mph |
| 70 mph | 73.3 mph |
| 80 mph | 83.7 mph |
Other sizes close to 225/55R18
- 225/55R18 vs 235/60R18+4.90%
- 225/55R18 vs 245/45R18-3.83%
- 225/55R18 vs 235/50R18-1.77%
- 225/55R18 vs 235/55R18+1.56%
- 225/55R18 vs 245/45R19-0.23%
- 225/55R18 vs 225/60R18+3.19%
- 225/55R18 vs 225/50R18-3.19%
- 225/55R18 vs 225/60R17-0.41%
- 225/55R18 vs 275/40R19-0.30%
- 225/55R18 vs 215/65R17+0.94%
- 225/55R18 vs 245/50R18-0.35%
- 225/55R18 vs 255/45R18-2.55%
Questions
Can I replace 225/55R18 with 255/55R18?
255/55R18 is outside the ±3% rule as a replacement for 225/55R18: the diameter differs by +4.68%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 225/55R18 and 255/55R18?
255/55R18 is 1.30" taller and 30 mm wider; the sidewall is +0.65". At an indicated 60 mph you'd actually be doing 62.8 mph.
Will 255/55R18 fit on 225/55R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.