255/45R19 vs 235/55R18
235/55R18 is a safe swap for 255/45R19 by the usual ±3% rule: the diameter differs by +0.51%.
Speedometer and odometer
With 235/55R18 on a car calibrated for 255/45R19, the speedometer reads 59.7 mph when you're really doing 60, and the odometer under-counts by 0.5%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.2 mph |
| 45 mph | 45.2 mph |
| 60 mph | 60.3 mph |
| 70 mph | 70.4 mph |
| 80 mph | 80.4 mph |
Other sizes close to 255/45R19
- 255/45R19 vs 235/55R19+4.07%
- 255/45R19 vs 245/45R19-1.26%
- 255/45R19 vs 245/40R19-4.70%
- 255/45R19 vs 255/50R19+3.58%
- 255/45R19 vs 255/40R19-3.58%
- 255/45R19 vs 225/55R19+2.53%
- 255/45R19 vs 275/40R19-1.33%
- 255/45R19 vs 255/40R20-0.01%
- 255/45R19 vs 225/45R19-3.79%
- 255/45R19 vs 235/50R19+0.77%
- 255/45R19 vs 285/35R19-4.21%
- 255/45R19 vs 235/45R19-2.53%
Questions
Can I replace 255/45R19 with 235/55R18?
235/55R18 is a safe swap for 255/45R19 by the usual ±3% rule: the diameter differs by +0.51%.
What's the difference between 255/45R19 and 235/55R18?
235/55R18 is 0.14" taller and 20 mm narrower; the sidewall is +0.57". At an indicated 60 mph you'd actually be doing 60.3 mph.
Will 235/55R18 fit on 255/45R19 wheels?
No — 255/45R19 needs a 19" wheel and 235/55R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.