255/30R19 vs 305/30R19
305/30R19 is outside the ±3% rule as a replacement for 255/30R19: the diameter differs by +4.72%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 305/30R19 on a car calibrated for 255/30R19, the speedometer reads 57.3 mph when you're really doing 60, and the odometer under-counts by 4.7%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.4 mph |
| 45 mph | 47.1 mph |
| 60 mph | 62.8 mph |
| 70 mph | 73.3 mph |
| 80 mph | 83.8 mph |
Other sizes close to 255/30R19
- 255/30R19 vs 225/40R18+0.25%
- 255/30R19 vs 255/35R19+4.01%
- 255/30R19 vs 255/35R18+0.02%
- 255/30R19 vs 245/35R19+2.91%
- 255/30R19 vs 225/40R19+4.25%
- 255/30R19 vs 235/35R19+1.81%
- 255/30R19 vs 285/30R19+2.83%
- 255/30R19 vs 225/35R19+0.71%
- 255/30R19 vs 295/30R19+3.78%
- 255/30R19 vs 275/30R19+1.89%
- 255/30R19 vs 265/30R19+0.94%
- 255/30R19 vs 295/30R18-0.22%
Questions
Can I replace 255/30R19 with 305/30R19?
305/30R19 is outside the ±3% rule as a replacement for 255/30R19: the diameter differs by +4.72%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 255/30R19 and 305/30R19?
305/30R19 is 1.18" taller and 50 mm wider; the sidewall is +0.59". At an indicated 60 mph you'd actually be doing 62.8 mph.
Will 305/30R19 fit on 255/30R19 wheels?
Both use a 19" rim, so the wheel diameter matches; check the wheel's width range for a 305 mm tire and the fender clearance.