235/40R17 vs 235/45R17
235/45R17 is outside the ±3% rule as a replacement for 235/40R17: the diameter differs by +3.79%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 235/45R17 on a car calibrated for 235/40R17, the speedometer reads 57.8 mph when you're really doing 60, and the odometer under-counts by 3.8%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.1 mph |
| 45 mph | 46.7 mph |
| 60 mph | 62.3 mph |
| 70 mph | 72.7 mph |
| 80 mph | 83.0 mph |
Other sizes close to 235/40R17
- 235/40R17 vs 225/45R17+2.34%
- 235/40R17 vs 215/45R17+0.89%
- 235/40R17 vs 205/50R17+2.74%
- 235/40R17 vs 215/50R17+4.36%
- 235/40R17 vs 205/45R17-0.56%
- 235/40R17 vs 245/40R17+1.29%
- 235/40R17 vs 255/40R17+2.58%
- 235/40R17 vs 195/55R16+0.18%
- 235/40R17 vs 205/40R17-3.87%
- 235/40R17 vs 205/40R18+0.23%
- 235/40R17 vs 215/40R17-2.58%
Questions
Can I replace 235/40R17 with 235/45R17?
235/45R17 is outside the ±3% rule as a replacement for 235/40R17: the diameter differs by +3.79%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 235/40R17 and 235/45R17?
235/45R17 is 0.93" taller and 0 mm wider; the sidewall is +0.46". At an indicated 60 mph you'd actually be doing 62.3 mph.
Will 235/45R17 fit on 235/40R17 wheels?
Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 235 mm tire and the fender clearance.