295/35R21 vs 285/40R21
285/40R21 is a safe swap for 295/35R21 by the usual ±3% rule: the diameter differs by +2.91%.
Speedometer and odometer
With 285/40R21 on a car calibrated for 295/35R21, the speedometer reads 58.3 mph when you're really doing 60, and the odometer under-counts by 2.9%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.9 mph |
| 45 mph | 46.3 mph |
| 60 mph | 61.7 mph |
| 70 mph | 72.0 mph |
| 80 mph | 82.3 mph |
Other sizes close to 295/35R21
- 295/35R21 vs 255/45R20-0.32%
- 295/35R21 vs 265/45R20+0.89%
- 295/35R21 vs 265/40R21+0.74%
- 295/35R21 vs 275/35R21-1.89%
- 295/35R21 vs 255/40R21-0.34%
- 295/35R21 vs 265/35R21-2.84%
- 295/35R21 vs 265/35R22+0.59%
- 295/35R21 vs 295/40R20+0.55%
- 295/35R21 vs 295/40R21+3.99%
- 295/35R21 vs 245/35R21-4.73%
- 295/35R21 vs 265/45R21+4.32%
- 295/35R21 vs 285/40R20-0.53%
Questions
Can I replace 295/35R21 with 285/40R21?
285/40R21 is a safe swap for 295/35R21 by the usual ±3% rule: the diameter differs by +2.91%.
What's the difference between 295/35R21 and 285/40R21?
285/40R21 is 0.85" taller and 10 mm narrower; the sidewall is +0.42". At an indicated 60 mph you'd actually be doing 61.7 mph.
Will 285/40R21 fit on 295/35R21 wheels?
Both use a 21" rim, so the wheel diameter matches; check the wheel's width range for a 285 mm tire and the fender clearance.