285/40R22 vs 255/50R21
255/50R21 is a safe swap for 285/40R22 by the usual ±3% rule: the diameter differs by +0.20%.
Speedometer and odometer
With 255/50R21 on a car calibrated for 285/40R22, the speedometer reads 59.9 mph when you're really doing 60, and the odometer under-counts by 0.2%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.1 mph |
| 70 mph | 70.1 mph |
| 80 mph | 80.2 mph |
Other sizes close to 285/40R22
- 285/40R22 vs 285/45R22+3.62%
- 285/40R22 vs 275/40R22-1.02%
- 285/40R22 vs 275/45R21-0.75%
- 285/40R22 vs 265/40R22-2.03%
- 285/40R22 vs 285/35R22-3.62%
- 285/40R22 vs 285/45R21+0.39%
- 285/40R22 vs 275/45R22+2.48%
- 285/40R22 vs 305/40R22+2.03%
- 285/40R22 vs 275/35R22-4.51%
- 285/40R22 vs 315/40R21-0.18%
- 285/40R22 vs 325/35R22-0.06%
- 285/40R22 vs 315/35R22-0.95%
Questions
Can I replace 285/40R22 with 255/50R21?
255/50R21 is a safe swap for 285/40R22 by the usual ±3% rule: the diameter differs by +0.20%.
What's the difference between 285/40R22 and 255/50R21?
255/50R21 is 0.06" taller and 30 mm narrower; the sidewall is +0.53". At an indicated 60 mph you'd actually be doing 60.1 mph.
Will 255/50R21 fit on 285/40R22 wheels?
No — 285/40R22 needs a 22" wheel and 255/50R21 a 21" wheel. This is a plus/minus-size swap that changes wheels too.