325/30R21 vs 285/30R22
285/30R22 is a safe swap for 325/30R21 by the usual ±3% rule: the diameter differs by +0.19%.
Speedometer and odometer
With 285/30R22 on a car calibrated for 325/30R21, 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 325/30R21
- 325/30R21 vs 245/45R20+0.01%
- 325/30R21 vs 275/40R20-0.05%
- 325/30R21 vs 265/40R21+2.33%
- 325/30R21 vs 315/35R20+0.01%
- 325/30R21 vs 275/35R21-0.34%
- 325/30R21 vs 295/35R21+1.58%
- 325/30R21 vs 255/40R21+1.24%
- 325/30R21 vs 265/35R21-1.30%
- 325/30R21 vs 245/35R21-3.23%
- 325/30R21 vs 305/35R20-0.95%
- 325/30R21 vs 285/40R21+4.53%
- 325/30R21 vs 275/40R21+3.43%
Questions
Can I replace 325/30R21 with 285/30R22?
285/30R22 is a safe swap for 325/30R21 by the usual ±3% rule: the diameter differs by +0.19%.
What's the difference between 325/30R21 and 285/30R22?
285/30R22 is 0.06" taller and 40 mm narrower; the sidewall is -0.47". At an indicated 60 mph you'd actually be doing 60.1 mph.
Will 285/30R22 fit on 325/30R21 wheels?
No — 325/30R21 needs a 21" wheel and 285/30R22 a 22" wheel. This is a plus/minus-size swap that changes wheels too.