255/30R19 vs 225/40R18
225/40R18 is a safe swap for 255/30R19 by the usual ±3% rule: the diameter differs by +0.25%.
Speedometer and odometer
With 225/40R18 on a car calibrated for 255/30R19, the speedometer reads 59.8 mph when you're really doing 60, and the odometer under-counts by 0.3%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.2 mph |
| 70 mph | 70.2 mph |
| 80 mph | 80.2 mph |
Other sizes close to 255/30R19
- 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 305/30R19+4.72%
- 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 225/40R18?
225/40R18 is a safe swap for 255/30R19 by the usual ±3% rule: the diameter differs by +0.25%.
What's the difference between 255/30R19 and 225/40R18?
225/40R18 is 0.06" taller and 30 mm narrower; the sidewall is +0.53". At an indicated 60 mph you'd actually be doing 60.2 mph.
Will 225/40R18 fit on 255/30R19 wheels?
No — 255/30R19 needs a 19" wheel and 225/40R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.