235/50R17 vs 265/40R18
265/40R18 is a safe swap for 235/50R17 by the usual ±3% rule: the diameter differs by +0.36%.
Speedometer and odometer
With 265/40R18 on a car calibrated for 235/50R17, the speedometer reads 59.8 mph when you're really doing 60, and the odometer under-counts by 0.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.2 mph |
| 60 mph | 60.2 mph |
| 70 mph | 70.3 mph |
| 80 mph | 80.3 mph |
Other sizes close to 235/50R17
- 235/50R17 vs 225/45R17-4.87%
- 235/50R17 vs 225/50R17-1.50%
- 235/50R17 vs 225/55R17+1.87%
- 235/50R17 vs 235/45R18+0.28%
- 235/50R17 vs 235/55R17+3.52%
- 235/50R17 vs 205/50R17-4.50%
- 235/50R17 vs 215/55R17+0.22%
- 235/50R17 vs 215/50R17-3.00%
- 235/50R17 vs 235/45R17-3.52%
- 235/50R17 vs 245/45R17-2.17%
- 235/50R17 vs 215/60R16-0.36%
- 235/50R17 vs 255/40R18-0.84%
Questions
Can I replace 235/50R17 with 265/40R18?
265/40R18 is a safe swap for 235/50R17 by the usual ±3% rule: the diameter differs by +0.36%.
What's the difference between 235/50R17 and 265/40R18?
265/40R18 is 0.09" taller and 30 mm wider; the sidewall is -0.45". At an indicated 60 mph you'd actually be doing 60.2 mph.
Will 265/40R18 fit on 235/50R17 wheels?
No — 235/50R17 needs a 17" wheel and 265/40R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.