245/50R17 vs 275/40R18
275/40R18 is a safe swap for 245/50R17 by the usual ±3% rule: the diameter differs by +0.06%.
Speedometer and odometer
With 275/40R18 on a car calibrated for 245/50R17, 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 245/50R17
- 245/50R17 vs 225/50R17-2.96%
- 245/50R17 vs 225/55R17+0.37%
- 245/50R17 vs 245/45R18+0.13%
- 245/50R17 vs 235/55R17+1.99%
- 245/50R17 vs 215/55R17-1.26%
- 245/50R17 vs 225/50R18+0.80%
- 245/50R17 vs 225/60R17+3.69%
- 245/50R17 vs 215/50R17-4.43%
- 245/50R17 vs 235/45R17-4.95%
- 245/50R17 vs 245/45R17-3.62%
- 245/50R17 vs 215/60R17+1.92%
- 245/50R17 vs 205/65R16-0.58%
Questions
Can I replace 245/50R17 with 275/40R18?
275/40R18 is a safe swap for 245/50R17 by the usual ±3% rule: the diameter differs by +0.06%.
What's the difference between 245/50R17 and 275/40R18?
275/40R18 is 0.02" taller and 30 mm wider; the sidewall is -0.49". At an indicated 60 mph you'd actually be doing 60.0 mph.
Will 275/40R18 fit on 245/50R17 wheels?
No — 245/50R17 needs a 17" wheel and 275/40R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.