315/30R19 vs 255/40R19
255/40R19 is a safe swap for 315/30R19 by the usual ±3% rule: the diameter differs by +2.23%.
Speedometer and odometer
With 255/40R19 on a car calibrated for 315/30R19, the speedometer reads 58.7 mph when you're really doing 60, and the odometer under-counts by 2.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.7 mph |
| 45 mph | 46.0 mph |
| 60 mph | 61.3 mph |
| 70 mph | 71.6 mph |
| 80 mph | 81.8 mph |
Other sizes close to 315/30R19
- 315/30R19 vs 245/45R18+0.91%
- 315/30R19 vs 235/45R18-0.43%
- 315/30R19 vs 245/45R19+4.69%
- 315/30R19 vs 245/40R19+1.04%
- 315/30R19 vs 235/40R19-0.15%
- 315/30R19 vs 255/35R19-1.56%
- 315/30R19 vs 275/35R19+0.52%
- 315/30R19 vs 275/40R19+4.62%
- 315/30R19 vs 245/35R19-2.61%
- 315/30R19 vs 225/40R19-1.34%
- 315/30R19 vs 235/35R19-3.65%
- 315/30R19 vs 225/45R19+2.01%
Questions
Can I replace 315/30R19 with 255/40R19?
255/40R19 is a safe swap for 315/30R19 by the usual ±3% rule: the diameter differs by +2.23%.
What's the difference between 315/30R19 and 255/40R19?
255/40R19 is 0.59" taller and 60 mm narrower; the sidewall is +0.30". At an indicated 60 mph you'd actually be doing 61.3 mph.
Will 255/40R19 fit on 315/30R19 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.