245/55R18 vs 235/65R18
235/65R18 is outside the ±3% rule as a replacement for 245/55R18: the diameter differs by +4.95%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 235/65R18 on a car calibrated for 245/55R18, the speedometer reads 57.2 mph when you're really doing 60, and the odometer under-counts by 5.0%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.5 mph |
| 45 mph | 47.2 mph |
| 60 mph | 63.0 mph |
| 70 mph | 73.5 mph |
| 80 mph | 84.0 mph |
Other sizes close to 245/55R18
- 245/55R18 vs 235/60R18+1.72%
- 245/55R18 vs 225/65R17-0.33%
- 245/55R18 vs 235/50R18-4.75%
- 245/55R18 vs 235/55R18-1.51%
- 245/55R18 vs 225/60R18+0.07%
- 245/55R18 vs 245/60R18+3.37%
- 245/55R18 vs 225/55R18-3.03%
- 245/55R18 vs 255/55R18+1.51%
- 245/55R18 vs 225/55R19+0.47%
- 245/55R18 vs 245/50R18-3.37%
- 245/55R18 vs 215/55R18-4.54%
- 245/55R18 vs 245/50R19+0.12%
Questions
Can I replace 245/55R18 with 235/65R18?
235/65R18 is outside the ±3% rule as a replacement for 245/55R18: the diameter differs by +4.95%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 245/55R18 and 235/65R18?
235/65R18 is 1.42" taller and 10 mm narrower; the sidewall is +0.71". At an indicated 60 mph you'd actually be doing 63.0 mph.
Will 235/65R18 fit on 245/55R18 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.