215/55R17 vs 235/45R18
235/45R18 is a safe swap for 215/55R17 by the usual ±3% rule: the diameter differs by +0.06%.
Speedometer and odometer
With 235/45R18 on a car calibrated for 215/55R17, the speedometer reads 60.0 mph when you're really doing 60, and the odometer under-counts by 0.1%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.0 mph |
| 45 mph | 45.0 mph |
| 60 mph | 60.0 mph |
| 70 mph | 70.0 mph |
| 80 mph | 80.0 mph |
Other sizes close to 215/55R17
- 215/55R17 vs 225/50R17-1.72%
- 215/55R17 vs 225/55R17+1.65%
- 215/55R17 vs 235/55R17+3.29%
- 215/55R17 vs 205/50R17-4.71%
- 215/55R17 vs 215/50R17-3.22%
- 215/55R17 vs 235/45R17-3.74%
- 215/55R17 vs 245/45R17-2.39%
- 215/55R17 vs 215/60R16-0.58%
- 215/55R17 vs 215/60R17+3.22%
- 215/55R17 vs 205/65R16+0.69%
- 215/55R17 vs 235/50R17-0.22%
- 215/55R17 vs 255/40R17-4.86%
Questions
Can I replace 215/55R17 with 235/45R18?
235/45R18 is a safe swap for 215/55R17 by the usual ±3% rule: the diameter differs by +0.06%.
What's the difference between 215/55R17 and 235/45R18?
235/45R18 is 0.02" taller and 20 mm wider; the sidewall is -0.49". At an indicated 60 mph you'd actually be doing 60.0 mph.
Will 235/45R18 fit on 215/55R17 wheels?
No — 215/55R17 needs a 17" wheel and 235/45R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.