33x12.50R18 vs 305/65R18
305/65R18 is a safe swap for 33x12.50R18 by the usual ±3% rule: the diameter differs by +1.85%.
Side by side
| 33x12.50R18 | 305/65R18 | Difference | |
|---|---|---|---|
| Overall diameter | 33.00" | 33.61" | +0.61" (+1.85%) |
| Section width | 318 mm | 305 mm | -13 mm |
| Sidewall | 7.50" | 7.81" | +0.31" |
| Rim | 18" | 18" | same |
| Circumference | 103.7" | 105.6" | +1.9" |
| Revs per mile | 611 | 600 | -11 |
| Ride height | — | — | +0.31" |
| Speedometer reads 60 mph | 60.0 | 61.1 | +1.1 mph |
Speedometer and odometer
With 305/65R18 on a car calibrated for 33x12.50R18, the speedometer reads 58.9 mph when you're really doing 60, and the odometer under-counts by 1.8%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.6 mph |
| 45 mph | 45.8 mph |
| 60 mph | 61.1 mph |
| 70 mph | 71.3 mph |
| 80 mph | 81.5 mph |
Other sizes close to 33x12.50R18
- 33x12.50R18 vs 275/65R18-2.80%
- 33x12.50R18 vs 275/70R18+0.48%
- 33x12.50R18 vs 285/70R17-0.88%
- 33x12.50R18 vs 265/65R18-4.35%
- 33x12.50R18 vs 265/70R18-1.19%
- 33x12.50R18 vs 255/70R18-2.86%
- 33x12.50R18 vs 285/65R18-1.25%
- 33x12.50R18 vs 295/70R18+3.82%
- 33x12.50R18 vs 295/70R17+0.79%
- 33x12.50R18 vs 285/60R18-4.65%
- 33x12.50R18 vs 33x12.50R170.00%
- 33x12.50R18 vs 325/65R18+4.95%
Questions
Can I replace 33x12.50R18 with 305/65R18?
305/65R18 is a safe swap for 33x12.50R18 by the usual ±3% rule: the diameter differs by +1.85%.
What's the difference between 33x12.50R18 and 305/65R18?
305/65R18 is 0.61" taller and 13 mm narrower; the sidewall is +0.31". At an indicated 60 mph you'd actually be doing 61.1 mph.
Will 305/65R18 fit on 33x12.50R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 305 mm tire and the fender clearance.