235/50R18 vs 235/55R18
235/55R18 is outside the ±3% rule as a replacement for 235/50R18: the diameter differs by +3.39%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 235/55R18 on a car calibrated for 235/50R18, the speedometer reads 58.0 mph when you're really doing 60, and the odometer under-counts by 3.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.0 mph |
| 45 mph | 46.5 mph |
| 60 mph | 62.0 mph |
| 70 mph | 72.4 mph |
| 80 mph | 82.7 mph |
Other sizes close to 235/50R18
- 235/50R18 vs 225/45R18-4.70%
- 235/50R18 vs 245/45R18-2.09%
- 235/50R18 vs 235/45R18-3.39%
- 235/50R18 vs 235/55R17-0.27%
- 235/50R18 vs 225/50R18-1.44%
- 235/50R18 vs 255/40R19-0.81%
- 235/50R18 vs 225/55R18+1.81%
- 235/50R18 vs 255/40R18-4.48%
- 235/50R18 vs 215/60R17-0.35%
- 235/50R18 vs 245/50R18+1.44%
- 235/50R18 vs 255/45R18-0.79%
- 235/50R18 vs 235/45R19+0.27%
Questions
Can I replace 235/50R18 with 235/55R18?
235/55R18 is outside the ±3% rule as a replacement for 235/50R18: the diameter differs by +3.39%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 235/50R18 and 235/55R18?
235/55R18 is 0.93" taller and 0 mm wider; the sidewall is +0.46". At an indicated 60 mph you'd actually be doing 62.0 mph.
Will 235/55R18 fit on 235/50R18 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.