255/30R20 vs 225/40R19
225/40R19 is a safe swap for 255/30R20 by the usual ±3% rule: the diameter differs by +0.24%.
Speedometer and odometer
With 225/40R19 on a car calibrated for 255/30R20, the speedometer reads 59.9 mph when you're really doing 60, and the odometer under-counts by 0.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.1 mph |
| 70 mph | 70.2 mph |
| 80 mph | 80.2 mph |
Other sizes close to 255/30R20
- 255/30R20 vs 255/35R19+0.02%
- 255/30R20 vs 245/35R20+2.80%
- 255/30R20 vs 255/35R20+3.86%
- 255/30R20 vs 285/30R20+2.72%
- 255/30R20 vs 275/30R20+1.82%
- 255/30R20 vs 265/35R20+4.92%
- 255/30R20 vs 235/35R20+1.74%
- 255/30R20 vs 295/30R20+3.63%
- 255/30R20 vs 305/30R20+4.54%
- 255/30R20 vs 305/30R19+0.70%
- 255/30R20 vs 295/30R19-0.21%
- 255/30R20 vs 245/30R20-0.91%
Questions
Can I replace 255/30R20 with 225/40R19?
225/40R19 is a safe swap for 255/30R20 by the usual ±3% rule: the diameter differs by +0.24%.
What's the difference between 255/30R20 and 225/40R19?
225/40R19 is 0.06" taller and 30 mm narrower; the sidewall is +0.53". At an indicated 60 mph you'd actually be doing 60.1 mph.
Will 225/40R19 fit on 255/30R20 wheels?
No — 255/30R20 needs a 20" wheel and 225/40R19 a 19" wheel. This is a plus/minus-size swap that changes wheels too.