255/55R19 vs 235/55R20
235/55R20 is a safe swap for 255/55R19 by the usual ±3% rule: the diameter differs by +0.45%.
Speedometer and odometer
With 235/55R20 on a car calibrated for 255/55R19, the speedometer reads 59.7 mph when you're really doing 60, and the odometer under-counts by 0.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.2 mph |
| 60 mph | 60.3 mph |
| 70 mph | 70.3 mph |
| 80 mph | 80.4 mph |
Other sizes close to 255/55R19
- 255/55R19 vs 235/55R19-2.88%
- 255/55R19 vs 255/50R19-3.34%
- 255/55R19 vs 255/50R20-0.01%
- 255/55R19 vs 235/65R18-0.05%
- 255/55R19 vs 275/45R20-1.00%
- 255/55R19 vs 225/55R19-4.32%
- 255/55R19 vs 245/55R19-1.44%
- 255/55R19 vs 255/60R19+3.34%
- 255/55R19 vs 265/50R19-2.03%
- 255/55R19 vs 245/50R19-4.65%
- 255/55R19 vs 255/60R18+0.01%
- 255/55R19 vs 275/55R19+2.88%
Questions
Can I replace 255/55R19 with 235/55R20?
235/55R20 is a safe swap for 255/55R19 by the usual ±3% rule: the diameter differs by +0.45%.
What's the difference between 255/55R19 and 235/55R20?
235/55R20 is 0.13" taller and 20 mm narrower; the sidewall is -0.43". At an indicated 60 mph you'd actually be doing 60.3 mph.
Will 235/55R20 fit on 255/55R19 wheels?
No — 255/55R19 needs a 19" wheel and 235/55R20 a 20" wheel. This is a plus/minus-size swap that changes wheels too.