255/40R22 vs 255/45R21
255/45R21 is a safe swap for 255/40R22 by the usual ±3% rule: the diameter differs by +0.01%.
Speedometer and odometer
With 255/45R21 on a car calibrated for 255/40R22, the speedometer reads 60.0 mph when you're really doing 60, and the odometer under-counts by 0.0%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.0 mph |
| 45 mph | 45.0 mph |
| 60 mph | 60.0 mph |
| 70 mph | 70.0 mph |
| 80 mph | 80.0 mph |
Other sizes close to 255/40R22
- 255/40R22 vs 275/40R22+2.10%
- 255/40R22 vs 265/40R22+1.05%
- 255/40R22 vs 265/35R22-2.43%
- 255/40R22 vs 285/35R22-0.59%
- 255/40R22 vs 285/40R22+3.15%
- 255/40R22 vs 295/40R21+0.87%
- 255/40R22 vs 285/40R21-0.18%
- 255/40R22 vs 275/35R22-1.51%
- 255/40R22 vs 295/35R22+0.33%
- 255/40R22 vs 315/35R22+2.16%
- 255/40R22 vs 325/35R22+3.08%
- 255/40R22 vs 285/30R22-4.33%
Questions
Can I replace 255/40R22 with 255/45R21?
255/45R21 is a safe swap for 255/40R22 by the usual ±3% rule: the diameter differs by +0.01%.
What's the difference between 255/40R22 and 255/45R21?
255/45R21 is 0.00" taller and 0 mm wider; the sidewall is +0.50". At an indicated 60 mph you'd actually be doing 60.0 mph.
Will 255/45R21 fit on 255/40R22 wheels?
No — 255/40R22 needs a 22" wheel and 255/45R21 a 21" wheel. This is a plus/minus-size swap that changes wheels too.