245/45R18 vs 225/55R17
225/55R17 is a safe swap for 245/45R18 by the usual ±3% rule: the diameter differs by +0.24%.
Speedometer and odometer
With 225/55R17 on a car calibrated for 245/45R18, the speedometer reads 59.9 mph when you're really doing 60, and the odometer under-counts by 0.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.1 mph |
| 70 mph | 70.2 mph |
| 80 mph | 80.2 mph |
Other sizes close to 245/45R18
- 245/45R18 vs 225/45R18-2.66%
- 245/45R18 vs 245/40R18-3.62%
- 245/45R18 vs 235/50R18+2.14%
- 245/45R18 vs 235/45R18-1.33%
- 245/45R18 vs 245/40R19+0.13%
- 245/45R18 vs 235/40R18-4.80%
- 245/45R18 vs 225/50R18+0.66%
- 245/45R18 vs 225/55R18+3.98%
- 245/45R18 vs 255/40R18-2.43%
- 245/45R18 vs 275/35R19-0.38%
- 245/45R18 vs 245/50R18+3.62%
- 245/45R18 vs 275/35R18-4.13%
Questions
Can I replace 245/45R18 with 225/55R17?
225/55R17 is a safe swap for 245/45R18 by the usual ±3% rule: the diameter differs by +0.24%.
What's the difference between 245/45R18 and 225/55R17?
225/55R17 is 0.06" taller and 20 mm narrower; the sidewall is +0.53". At an indicated 60 mph you'd actually be doing 60.1 mph.
Will 225/55R17 fit on 245/45R18 wheels?
No — 245/45R18 needs a 18" wheel and 225/55R17 a 17" wheel. This is a plus/minus-size swap that changes wheels too.