33x12.50R18 vs 325/65R18
325/65R18 is outside the ±3% rule as a replacement for 33x12.50R18: the diameter differs by +4.95%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Side by side
| 33x12.50R18 | 325/65R18 | Difference | |
|---|---|---|---|
| Overall diameter | 33.00" | 34.63" | +1.63" (+4.95%) |
| Section width | 318 mm | 325 mm | +7 mm |
| Sidewall | 7.50" | 8.32" | +0.82" |
| Rim | 18" | 18" | same |
| Circumference | 103.7" | 108.8" | +5.1" |
| Revs per mile | 611 | 582 | -29 |
| Ride height | — | — | +0.82" |
| Speedometer reads 60 mph | 60.0 | 63.0 | +3.0 mph |
Speedometer and odometer
With 325/65R18 on a car calibrated for 33x12.50R18, the speedometer reads 57.2 mph when you're really doing 60, and the odometer under-counts by 5.0%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.5 mph |
| 45 mph | 47.2 mph |
| 60 mph | 63.0 mph |
| 70 mph | 73.5 mph |
| 80 mph | 84.0 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 255/80R17+0.19%
Questions
Can I replace 33x12.50R18 with 325/65R18?
325/65R18 is outside the ±3% rule as a replacement for 33x12.50R18: the diameter differs by +4.95%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 33x12.50R18 and 325/65R18?
325/65R18 is 1.63" taller and 7 mm wider; the sidewall is +0.82". At an indicated 60 mph you'd actually be doing 63.0 mph.
Will 325/65R18 fit on 33x12.50R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 325 mm tire and the fender clearance.