225/50R18 vs 255/45R18
255/45R18 is a safe swap for 225/50R18 by the usual ±3% rule: the diameter differs by +0.66%.
Speedometer and odometer
With 255/45R18 on a car calibrated for 225/50R18, the speedometer reads 59.6 mph when you're really doing 60, and the odometer under-counts by 0.7%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.2 mph |
| 45 mph | 45.3 mph |
| 60 mph | 60.4 mph |
| 70 mph | 70.5 mph |
| 80 mph | 80.5 mph |
Other sizes close to 225/50R18
- 225/50R18 vs 225/45R18-3.30%
- 225/50R18 vs 245/40R18-4.25%
- 225/50R18 vs 225/55R17-0.43%
- 225/50R18 vs 245/45R18-0.66%
- 225/50R18 vs 235/50R18+1.47%
- 225/50R18 vs 235/45R18-1.98%
- 225/50R18 vs 235/55R18+4.91%
- 225/50R18 vs 245/40R19-0.53%
- 225/50R18 vs 255/40R19+0.64%
- 225/50R18 vs 225/55R18+3.30%
- 225/50R18 vs 255/40R18-3.08%
- 225/50R18 vs 225/45R19+0.43%
Questions
Can I replace 225/50R18 with 255/45R18?
255/45R18 is a safe swap for 225/50R18 by the usual ±3% rule: the diameter differs by +0.66%.
What's the difference between 225/50R18 and 255/45R18?
255/45R18 is 0.18" taller and 30 mm wider; the sidewall is +0.09". At an indicated 60 mph you'd actually be doing 60.4 mph.
Will 255/45R18 fit on 225/50R18 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.