255/40R19 vs 255/45R19
255/45R19 is outside the ±3% rule as a replacement for 255/40R19: the diameter differs by +3.71%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/45R19 on a car calibrated for 255/40R19, the speedometer reads 57.9 mph when you're really doing 60, and the odometer under-counts by 3.7%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.1 mph |
| 45 mph | 46.7 mph |
| 60 mph | 62.2 mph |
| 70 mph | 72.6 mph |
| 80 mph | 83.0 mph |
Other sizes close to 255/40R19
- 255/40R19 vs 235/50R18+0.82%
- 255/40R19 vs 245/45R19+2.40%
- 255/40R19 vs 245/40R19-1.17%
- 255/40R19 vs 225/50R18-0.64%
- 255/40R19 vs 235/40R19-2.33%
- 255/40R19 vs 255/35R19-3.71%
- 255/40R19 vs 275/35R19-1.67%
- 255/40R19 vs 275/40R19+2.33%
- 255/40R19 vs 245/35R19-4.73%
- 255/40R19 vs 255/35R20-0.01%
- 255/40R19 vs 225/40R19-3.50%
- 255/40R19 vs 225/45R19-0.22%
Questions
Can I replace 255/40R19 with 255/45R19?
255/45R19 is outside the ±3% rule as a replacement for 255/40R19: the diameter differs by +3.71%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 255/40R19 and 255/45R19?
255/45R19 is 1.00" taller and 0 mm wider; the sidewall is +0.50". At an indicated 60 mph you'd actually be doing 62.2 mph.
Will 255/45R19 fit on 255/40R19 wheels?
Both use a 19" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.