33x12.50R20 vs 305/55R20
305/55R20 is a safe swap for 33x12.50R20 by the usual ±3% rule: the diameter differs by +0.63%.
Side by side
| 33x12.50R20 | 305/55R20 | Difference | |
|---|---|---|---|
| Overall diameter | 33.00" | 33.21" | +0.21" (+0.63%) |
| Section width | 318 mm | 305 mm | -13 mm |
| Sidewall | 6.50" | 6.60" | +0.10" |
| Rim | 20" | 20" | same |
| Circumference | 103.7" | 104.3" | +0.7" |
| Revs per mile | 611 | 607 | -4 |
| Ride height | — | — | +0.10" |
| Speedometer reads 60 mph | 60.0 | 60.4 | +0.4 mph |
Speedometer and odometer
With 305/55R20 on a car calibrated for 33x12.50R20, the speedometer reads 59.6 mph when you're really doing 60, and the odometer under-counts by 0.6%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.2 mph |
| 45 mph | 45.3 mph |
| 60 mph | 60.4 mph |
| 70 mph | 70.4 mph |
| 80 mph | 80.5 mph |
Other sizes close to 33x12.50R20
- 33x12.50R20 vs 275/55R20-3.30%
- 33x12.50R20 vs 275/60R20-0.02%
- 33x12.50R20 vs 275/65R20+3.26%
- 33x12.50R20 vs 265/60R20-1.46%
- 33x12.50R20 vs 285/55R20-1.99%
- 33x12.50R20 vs 285/60R20+1.41%
- 33x12.50R20 vs 295/60R20+2.84%
- 33x12.50R20 vs 295/55R20-0.68%
- 33x12.50R20 vs 285/65R20+4.81%
- 33x12.50R20 vs 245/60R20-4.32%
- 33x12.50R20 vs 305/50R20-3.01%
- 33x12.50R20 vs 255/60R20-2.89%
Questions
Can I replace 33x12.50R20 with 305/55R20?
305/55R20 is a safe swap for 33x12.50R20 by the usual ±3% rule: the diameter differs by +0.63%.
What's the difference between 33x12.50R20 and 305/55R20?
305/55R20 is 0.21" taller and 13 mm narrower; the sidewall is +0.10". At an indicated 60 mph you'd actually be doing 60.4 mph.
Will 305/55R20 fit on 33x12.50R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 305 mm tire and the fender clearance.