225/45R18 vs 235/50R18
235/50R18 is outside the ±3% rule as a replacement for 225/45R18: the diameter differs by +4.93%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 235/50R18 on a car calibrated for 225/45R18, the speedometer reads 57.2 mph when you're really doing 60, and the odometer under-counts by 4.9%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.5 mph |
| 45 mph | 47.2 mph |
| 60 mph | 63.0 mph |
| 70 mph | 73.4 mph |
| 80 mph | 83.9 mph |
Other sizes close to 225/45R18
- 225/45R18 vs 245/40R18-0.99%
- 225/45R18 vs 225/40R18-3.41%
- 225/45R18 vs 225/50R17-0.44%
- 225/45R18 vs 245/45R18+2.73%
- 225/45R18 vs 235/45R18+1.36%
- 225/45R18 vs 235/40R18-2.20%
- 225/45R18 vs 225/50R18+3.41%
- 225/45R18 vs 255/35R19+0.21%
- 225/45R18 vs 255/35R18-3.64%
- 225/45R18 vs 255/40R18+0.23%
- 225/45R18 vs 245/35R19-0.85%
- 225/45R18 vs 225/40R19+0.44%
Questions
Can I replace 225/45R18 with 235/50R18?
235/50R18 is outside the ±3% rule as a replacement for 225/45R18: the diameter differs by +4.93%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 225/45R18 and 235/50R18?
235/50R18 is 1.28" taller and 10 mm wider; the sidewall is +0.64". At an indicated 60 mph you'd actually be doing 63.0 mph.
Will 235/50R18 fit on 225/45R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 235 mm tire and the fender clearance.