245/40R21 vs 285/30R22
285/30R22 is a safe swap for 245/40R21 by the usual ±3% rule: the diameter differs by +0.05%.
Speedometer and odometer
With 285/30R22 on a car calibrated for 245/40R21, the speedometer reads 60.0 mph when you're really doing 60, and the odometer under-counts by 0.1%.
| 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 245/40R21
- 245/40R21 vs 245/45R20-0.12%
- 245/40R21 vs 275/40R20-0.19%
- 245/40R21 vs 265/40R21+2.19%
- 245/40R21 vs 315/35R20-0.12%
- 245/40R21 vs 275/35R21-0.48%
- 245/40R21 vs 295/35R21+1.44%
- 245/40R21 vs 255/40R21+1.10%
- 245/40R21 vs 265/35R21-1.44%
- 245/40R21 vs 245/35R21-3.36%
- 245/40R21 vs 285/40R21+4.39%
- 245/40R21 vs 285/40R20+0.90%
- 245/40R21 vs 325/30R21-0.14%
Questions
Can I replace 245/40R21 with 285/30R22?
285/30R22 is a safe swap for 245/40R21 by the usual ±3% rule: the diameter differs by +0.05%.
What's the difference between 245/40R21 and 285/30R22?
285/30R22 is 0.02" taller and 40 mm wider; the sidewall is -0.49". At an indicated 60 mph you'd actually be doing 60.0 mph.
Will 285/30R22 fit on 245/40R21 wheels?
No — 245/40R21 needs a 21" wheel and 285/30R22 a 22" wheel. This is a plus/minus-size swap that changes wheels too.