205/45R17 vs 255/40R17
255/40R17 is outside the ±3% rule as a replacement for 205/45R17: the diameter differs by +3.16%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/40R17 on a car calibrated for 205/45R17, the speedometer reads 58.2 mph when you're really doing 60, and the odometer under-counts by 3.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.9 mph |
| 45 mph | 46.4 mph |
| 60 mph | 61.9 mph |
| 70 mph | 72.2 mph |
| 80 mph | 82.5 mph |
Other sizes close to 205/45R17
- 205/45R17 vs 225/45R17+2.92%
- 205/45R17 vs 215/45R17+1.46%
- 205/45R17 vs 205/50R17+3.33%
- 205/45R17 vs 215/50R17+4.95%
- 205/45R17 vs 235/45R17+4.38%
- 205/45R17 vs 245/40R17+1.87%
- 205/45R17 vs 195/55R16+0.75%
- 205/45R17 vs 205/50R16-0.80%
- 205/45R17 vs 205/40R17-3.33%
- 205/45R17 vs 235/40R17+0.57%
- 205/45R17 vs 205/40R18+0.80%
- 205/45R17 vs 215/40R17-2.03%
Questions
Can I replace 205/45R17 with 255/40R17?
255/40R17 is outside the ±3% rule as a replacement for 205/45R17: the diameter differs by +3.16%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 205/45R17 and 255/40R17?
255/40R17 is 0.77" taller and 50 mm wider; the sidewall is +0.38". At an indicated 60 mph you'd actually be doing 61.9 mph.
Will 255/40R17 fit on 205/45R17 wheels?
Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.