275/45R20 vs 255/55R20
255/55R20 is outside the ±3% rule as a replacement for 275/45R20: the diameter differs by +4.37%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/55R20 on a car calibrated for 275/45R20, the speedometer reads 57.5 mph when you're really doing 60, and the odometer under-counts by 4.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.3 mph |
| 45 mph | 47.0 mph |
| 60 mph | 62.6 mph |
| 70 mph | 73.1 mph |
| 80 mph | 83.5 mph |
Other sizes close to 275/45R20
- 275/45R20 vs 245/45R20-3.57%
- 275/45R20 vs 255/45R20-2.38%
- 275/45R20 vs 255/50R20+0.99%
- 275/45R20 vs 275/40R20-3.64%
- 275/45R20 vs 265/50R20+2.32%
- 275/45R20 vs 245/50R20-0.33%
- 275/45R20 vs 235/55R20+1.46%
- 275/45R20 vs 245/55R19-0.45%
- 275/45R20 vs 265/45R20-1.19%
- 275/45R20 vs 315/35R20-3.57%
- 275/45R20 vs 275/50R20+3.64%
- 275/45R20 vs 295/40R20-1.52%
Questions
Can I replace 275/45R20 with 255/55R20?
255/55R20 is outside the ±3% rule as a replacement for 275/45R20: the diameter differs by +4.37%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 275/45R20 and 255/55R20?
255/55R20 is 1.30" taller and 20 mm narrower; the sidewall is +0.65". At an indicated 60 mph you'd actually be doing 62.6 mph.
Will 255/55R20 fit on 275/45R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.