285/55R20 vs 33x12.50R20
33x12.50R20 is a safe swap for 285/55R20 by the usual ±3% rule: the diameter differs by +2.03%.
Side by side
| 285/55R20 | 33x12.50R20 | Difference | |
|---|---|---|---|
| Overall diameter | 32.34" | 33.00" | +0.66" (+2.03%) |
| Section width | 285 mm | 318 mm | +33 mm |
| Sidewall | 6.17" | 6.50" | +0.33" |
| Rim | 20" | 20" | same |
| Circumference | 101.6" | 103.7" | +2.1" |
| Revs per mile | 624 | 611 | -12 |
| Ride height | — | — | +0.33" |
| Speedometer reads 60 mph | 60.0 | 61.2 | +1.2 mph |
Speedometer and odometer
With 33x12.50R20 on a car calibrated for 285/55R20, the speedometer reads 58.8 mph when you're really doing 60, and the odometer under-counts by 2.0%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.6 mph |
| 45 mph | 45.9 mph |
| 60 mph | 61.2 mph |
| 70 mph | 71.4 mph |
| 80 mph | 81.6 mph |
Other sizes close to 285/55R20
- 285/55R20 vs 275/55R20-1.34%
- 285/55R20 vs 275/60R20+2.01%
- 285/55R20 vs 255/55R20-4.02%
- 285/55R20 vs 265/60R20+0.55%
- 285/55R20 vs 305/55R20+2.68%
- 285/55R20 vs 285/60R20+3.47%
- 285/55R20 vs 275/50R20-4.69%
- 285/55R20 vs 295/60R20+4.93%
- 285/55R20 vs 295/55R20+1.34%
- 285/55R20 vs 285/50R20-3.47%
- 285/55R20 vs 245/60R20-2.37%
- 285/55R20 vs 305/50R20-1.03%
Questions
Can I replace 285/55R20 with 33x12.50R20?
33x12.50R20 is a safe swap for 285/55R20 by the usual ±3% rule: the diameter differs by +2.03%.
What's the difference between 285/55R20 and 33x12.50R20?
33x12.50R20 is 0.66" taller and 33 mm wider; the sidewall is +0.33". At an indicated 60 mph you'd actually be doing 61.2 mph.
Will 33x12.50R20 fit on 285/55R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 318 mm tire and the fender clearance.