33x12.50R18 vs 285/75R18
285/75R18 is 5.5% taller (+1.83 in) and 1.28 in narrower than 33x12.50R18.
285/75R18 is 5.5% taller than 33x12.50R18. Beyond 5% you usually need a lift or leveling kit, a speedometer recalibration and sometimes new gears.
| 33x12.50R18 | 285/75R18 | Change | |
|---|---|---|---|
| Diameter | 33.00″ | 34.83″ | +1.83″+5.5% |
| Width | 12.50″ | 11.22″ | −1.28″−10.2% |
| Sidewall | 7.50″ | 8.42″ | +0.92″+12.2% |
| Circumference | 103.7″ | 109.4″ | +5.8″+5.5% |
| Wheel | 18″ | 18″ | Same |
| Revs per mile | 611 | 579 | −32 |
Real speed on 285/75R18.
Change in height under the axle.
On the same wheel, split inboard and outboard.
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33x12.50R18 or 285/75R18?
Can I use 285/75R18 instead of 33x12.50R18?
285/75R18 is 5.5% taller than 33x12.50R18. Beyond 5% you usually need a lift or leveling kit, a speedometer recalibration and sometimes new gears. Also match or beat the original load index and speed rating, and check that the wheel width suits the new tire.
Will my speedometer be off?
At an indicated 60 mph on 285/75R18 you are really doing 63.3 mph if the speedometer was set up for 33x12.50R18. Going the other way, 33x12.50R18 would make it read 56.8 mph at a real 60.
How much ground clearance does it change?
Half the diameter difference: +0.92 in (+23 mm) under the axle.