255/50R21 vs 275/50R21
275/50R21 is a safe swap for 255/50R21 by the usual ±3% rule: the diameter differs by +2.54%.
Speedometer and odometer
With 275/50R21 on a car calibrated for 255/50R21, the speedometer reads 58.5 mph when you're really doing 60, and the odometer under-counts by 2.5%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.8 mph |
| 45 mph | 46.1 mph |
| 60 mph | 61.5 mph |
| 70 mph | 71.8 mph |
| 80 mph | 82.0 mph |
Other sizes close to 255/50R21
- 255/50R21 vs 255/55R20+0.01%
- 255/50R21 vs 275/50R20-0.68%
- 255/50R21 vs 275/45R21-0.95%
- 255/50R21 vs 285/40R22-0.20%
- 255/50R21 vs 285/45R21+0.19%
- 255/50R21 vs 295/40R21-2.41%
- 255/50R21 vs 285/50R20+0.58%
- 255/50R21 vs 265/45R21-2.09%
- 255/50R21 vs 285/40R21-3.42%
- 255/50R21 vs 275/40R21-4.44%
- 255/50R21 vs 315/35R21-4.38%
- 255/50R21 vs 315/40R21-0.38%
Questions
Can I replace 255/50R21 with 275/50R21?
275/50R21 is a safe swap for 255/50R21 by the usual ±3% rule: the diameter differs by +2.54%.
What's the difference between 255/50R21 and 275/50R21?
275/50R21 is 0.79" taller and 20 mm wider; the sidewall is +0.39". At an indicated 60 mph you'd actually be doing 61.5 mph.
Will 275/50R21 fit on 255/50R21 wheels?
Both use a 21" rim, so the wheel diameter matches; check the wheel's width range for a 275 mm tire and the fender clearance.