345/30R19 vs 255/45R19
255/45R19 is outside the ±3% rule as a replacement for 345/30R19: the diameter differs by +3.26%, 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 345/30R19, the speedometer reads 58.1 mph when you're really doing 60, and the odometer under-counts by 3.3%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.0 mph |
| 45 mph | 46.5 mph |
| 60 mph | 62.0 mph |
| 70 mph | 72.3 mph |
| 80 mph | 82.6 mph |
Other sizes close to 345/30R19
- 345/30R19 vs 235/50R18+0.38%
- 345/30R19 vs 245/45R19+1.96%
- 345/30R19 vs 245/40R19-1.60%
- 345/30R19 vs 235/40R19-2.76%
- 345/30R19 vs 255/40R19-0.44%
- 345/30R19 vs 255/35R19-4.13%
- 345/30R19 vs 275/35R19-2.10%
- 345/30R19 vs 275/40R19+1.89%
- 345/30R19 vs 255/35R20-0.45%
- 345/30R19 vs 225/40R19-3.92%
- 345/30R19 vs 225/45R19-0.65%
- 345/30R19 vs 235/50R19+4.06%
Questions
Can I replace 345/30R19 with 255/45R19?
255/45R19 is outside the ±3% rule as a replacement for 345/30R19: the diameter differs by +3.26%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 345/30R19 and 255/45R19?
255/45R19 is 0.89" taller and 90 mm narrower; the sidewall is +0.44". At an indicated 60 mph you'd actually be doing 62.0 mph.
Will 255/45R19 fit on 345/30R19 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.