255/55R20 vs 275/55R20
275/55R20 is a safe swap for 255/55R20 by the usual ±3% rule: the diameter differs by +2.79%.
Speedometer and odometer
With 275/55R20 on a car calibrated for 255/55R20, the speedometer reads 58.4 mph when you're really doing 60, and the odometer under-counts by 2.8%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.8 mph |
| 45 mph | 46.3 mph |
| 60 mph | 61.7 mph |
| 70 mph | 72.0 mph |
| 80 mph | 82.2 mph |
Other sizes close to 255/55R20
- 255/55R20 vs 255/50R20-3.23%
- 255/55R20 vs 265/50R20-1.97%
- 255/55R20 vs 245/50R20-4.50%
- 255/55R20 vs 275/45R20-4.19%
- 255/55R20 vs 235/55R20-2.79%
- 255/55R20 vs 255/60R19+0.01%
- 255/55R20 vs 265/60R20+4.76%
- 255/55R20 vs 285/55R20+4.19%
- 255/55R20 vs 275/50R20-0.70%
- 255/55R20 vs 275/45R21-0.96%
- 255/55R20 vs 285/50R20+0.57%
- 255/55R20 vs 285/45R21+0.18%
Questions
Can I replace 255/55R20 with 275/55R20?
275/55R20 is a safe swap for 255/55R20 by the usual ±3% rule: the diameter differs by +2.79%.
What's the difference between 255/55R20 and 275/55R20?
275/55R20 is 0.87" taller and 20 mm wider; the sidewall is +0.43". At an indicated 60 mph you'd actually be doing 61.7 mph.
Will 275/55R20 fit on 255/55R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 275 mm tire and the fender clearance.