305/60R18 vs 33x12.50R18
33x12.50R18 is a safe swap for 305/60R18 by the usual ±3% rule: the diameter differs by +1.82%.
Side by side
| 305/60R18 | 33x12.50R18 | Difference | |
|---|---|---|---|
| Overall diameter | 32.41" | 33.00" | +0.59" (+1.82%) |
| Section width | 305 mm | 318 mm | +13 mm |
| Sidewall | 7.20" | 7.50" | +0.30" |
| Rim | 18" | 18" | same |
| Circumference | 101.8" | 103.7" | +1.9" |
| Revs per mile | 622 | 611 | -11 |
| Ride height | — | — | +0.30" |
| Speedometer reads 60 mph | 60.0 | 61.1 | +1.1 mph |
Speedometer and odometer
With 33x12.50R18 on a car calibrated for 305/60R18, 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 | 30.5 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 305/60R18
- 305/60R18 vs 275/65R18-1.03%
- 305/60R18 vs 275/70R18+2.31%
- 305/60R18 vs 285/70R17+0.92%
- 305/60R18 vs 265/65R18-2.61%
- 305/60R18 vs 265/70R18+0.61%
- 305/60R18 vs 255/70R18-1.09%
- 305/60R18 vs 255/65R18-4.19%
- 305/60R18 vs 285/65R18+0.55%
- 305/60R18 vs 285/60R18-2.92%
- 305/60R18 vs 275/70R17-0.78%
- 305/60R18 vs 305/65R18+3.71%
- 305/60R18 vs 275/60R18-4.37%
Questions
Can I replace 305/60R18 with 33x12.50R18?
33x12.50R18 is a safe swap for 305/60R18 by the usual ±3% rule: the diameter differs by +1.82%.
What's the difference between 305/60R18 and 33x12.50R18?
33x12.50R18 is 0.59" taller and 13 mm wider; the sidewall is +0.30". At an indicated 60 mph you'd actually be doing 61.1 mph.
Will 33x12.50R18 fit on 305/60R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 318 mm tire and the fender clearance.