215/50R18 vs 255/45R18
255/45R18 is a safe swap for 215/50R18 by the usual ±3% rule: the diameter differs by +2.16%.
Speedometer and odometer
With 255/45R18 on a car calibrated for 215/50R18, the speedometer reads 58.7 mph when you're really doing 60, and the odometer under-counts by 2.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.6 mph |
| 45 mph | 46.0 mph |
| 60 mph | 61.3 mph |
| 70 mph | 71.5 mph |
| 80 mph | 81.7 mph |
Other sizes close to 215/50R18
- 215/50R18 vs 225/45R18-1.86%
- 215/50R18 vs 245/40R18-2.83%
- 215/50R18 vs 245/45R18+0.82%
- 215/50R18 vs 235/50R18+2.98%
- 215/50R18 vs 235/45R18-0.52%
- 215/50R18 vs 245/40R19+0.95%
- 215/50R18 vs 215/55R17-0.58%
- 215/50R18 vs 235/40R18-4.02%
- 215/50R18 vs 225/50R18+1.49%
- 215/50R18 vs 235/40R19-0.24%
- 215/50R18 vs 225/55R18+4.83%
- 215/50R18 vs 255/40R18-1.64%
Questions
Can I replace 215/50R18 with 255/45R18?
255/45R18 is a safe swap for 215/50R18 by the usual ±3% rule: the diameter differs by +2.16%.
What's the difference between 215/50R18 and 255/45R18?
255/45R18 is 0.57" taller and 40 mm wider; the sidewall is +0.29". At an indicated 60 mph you'd actually be doing 61.3 mph.
Will 255/45R18 fit on 215/50R18 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.