245/40R19 vs 255/45R19
255/45R19 is outside the ±3% rule as a replacement for 245/40R19: the diameter differs by +4.94%, 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 245/40R19, the speedometer reads 57.2 mph when you're really doing 60, and the odometer under-counts by 4.9%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.5 mph |
| 45 mph | 47.2 mph |
| 60 mph | 63.0 mph |
| 70 mph | 73.5 mph |
| 80 mph | 83.9 mph |
Other sizes close to 245/40R19
- 245/40R19 vs 245/45R18-0.13%
- 245/40R19 vs 245/45R19+3.61%
- 245/40R19 vs 225/50R18+0.53%
- 245/40R19 vs 235/40R19-1.18%
- 245/40R19 vs 255/40R19+1.18%
- 245/40R19 vs 255/35R19-2.58%
- 245/40R19 vs 275/35R19-0.52%
- 245/40R19 vs 275/40R19+3.54%
- 245/40R19 vs 245/35R20+0.13%
- 245/40R19 vs 245/35R19-3.61%
- 245/40R19 vs 225/40R19-2.36%
- 245/40R19 vs 235/35R19-4.64%
Questions
Can I replace 245/40R19 with 255/45R19?
255/45R19 is outside the ±3% rule as a replacement for 245/40R19: the diameter differs by +4.94%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 245/40R19 and 255/45R19?
255/45R19 is 1.32" taller and 10 mm wider; the sidewall is +0.66". At an indicated 60 mph you'd actually be doing 63.0 mph.
Will 255/45R19 fit on 245/40R19 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.