215/45R18 vs 225/50R18
225/50R18 is outside the ±3% rule as a replacement for 215/45R18: the diameter differs by +4.84%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 225/50R18 on a car calibrated for 215/45R18, the speedometer reads 57.2 mph when you're really doing 60, and the odometer under-counts by 4.8%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.5 mph |
| 45 mph | 47.2 mph |
| 60 mph | 62.9 mph |
| 70 mph | 73.4 mph |
| 80 mph | 83.9 mph |
Other sizes close to 215/45R18
- 215/45R18 vs 245/40R18+0.38%
- 215/45R18 vs 225/45R18+1.38%
- 215/45R18 vs 225/40R18-2.07%
- 215/45R18 vs 225/50R17+0.94%
- 215/45R18 vs 245/45R18+4.15%
- 215/45R18 vs 235/45R18+2.77%
- 215/45R18 vs 235/40R18-0.85%
- 215/45R18 vs 215/50R17-0.60%
- 215/45R18 vs 245/45R17+0.25%
- 215/45R18 vs 255/35R18-2.31%
- 215/45R18 vs 255/40R18+1.61%
- 215/45R18 vs 245/35R19+0.52%
Questions
Can I replace 215/45R18 with 225/50R18?
225/50R18 is outside the ±3% rule as a replacement for 215/45R18: the diameter differs by +4.84%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 215/45R18 and 225/50R18?
225/50R18 is 1.24" taller and 10 mm wider; the sidewall is +0.62". At an indicated 60 mph you'd actually be doing 62.9 mph.
Will 225/50R18 fit on 215/45R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 225 mm tire and the fender clearance.