285/30R19 vs 255/40R19
255/40R19 is outside the ±3% rule as a replacement for 285/30R19: the diameter differs by +5.05%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/40R19 on a car calibrated for 285/30R19, the speedometer reads 57.1 mph when you're really doing 60, and the odometer under-counts by 5.0%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.5 mph |
| 45 mph | 47.3 mph |
| 60 mph | 63.0 mph |
| 70 mph | 73.5 mph |
| 80 mph | 84.0 mph |
Other sizes close to 285/30R19
- 285/30R19 vs 245/40R18-0.06%
- 285/30R19 vs 225/45R18+0.93%
- 285/30R19 vs 245/40R19+3.82%
- 285/30R19 vs 235/40R19+2.60%
- 285/30R19 vs 255/35R19+1.15%
- 285/30R19 vs 275/35R19+3.29%
- 285/30R19 vs 245/35R19+0.08%
- 285/30R19 vs 225/40R19+1.38%
- 285/30R19 vs 235/35R19-0.99%
- 285/30R19 vs 225/45R19+4.82%
- 285/30R19 vs 275/35R18-0.60%
- 285/30R19 vs 285/35R19+4.36%
Questions
Can I replace 285/30R19 with 255/40R19?
255/40R19 is outside the ±3% rule as a replacement for 285/30R19: the diameter differs by +5.05%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 285/30R19 and 255/40R19?
255/40R19 is 1.30" taller and 30 mm narrower; the sidewall is +0.65". At an indicated 60 mph you'd actually be doing 63.0 mph.
Will 255/40R19 fit on 285/30R19 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.