TireSizesFinder

285/75R17 vs 33x12.50R18

33x12.50R18 is 0.83 in (21.1 mm) shorter than 285/75R17, a −2.46% diameter difference. With the speedometer set for 285/75R17, an indicated 60 mph is 58.5 mph on 33x12.50R18.

Is this a safe swap?

Diameter difference −2.46%: within the ±3% guideline

By overall diameter alone, 33x12.50R18 falls inside the ±3% range commonly used as a guideline when replacing 285/75R17. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 285/75R17 (33.83 in) vs 33x12.50R18 (33.00 in)285/75R1733.83 in × 11.22 in33x12.50R1833.00 in × 12.50 in
Side profile and tread width, drawn to the same scale.
285/75R17 vs 33x12.50R18 differences
Measurement285/75R1733x12.50R18Difference% diff
Overall diameter33.83 in (859.3 mm)33.00 in (838.2 mm)−0.83 in (−21.1 mm)−2.46%
Sidewall height8.42 in (213.8 mm)7.50 in (190.5 mm)−0.92 in (−23.2 mm)−10.88%
Section width11.22 in (285.0 mm)12.50 in (317.5 mm)+1.28 in (+32.5 mm)+11.40%
Circumference106.28 in (2,699.6 mm)103.67 in (2,633.3 mm)−2.61 in (−66.3 mm)−2.46%
Revolutions per mile596611+15+2.52%
True speed with the speedometer calibrated for 285/75R17
IndicatedActual on 285/75R17Actual on 33x12.50R18Difference
30 mph30.0 mph29.3 mph−0.7 mph
60 mph60.0 mph58.5 mph−1.5 mph
75 mph75.0 mph73.2 mph−1.8 mph

Ride-height change: 33x12.50R18 lowers the vehicle by 0.42 in (10.5 mm) at the axle (half the −21.1 mm diameter difference).

33x12.50R18 is 0.83 in shorter than 285/75R17 and 33 mm wider, a 2.46% difference in overall diameter.

With the speedometer calibrated for 285/75R17, an indicated 60 mph is actually 58.5 mph on 33x12.50R18, and revolutions per mile change from 596 to 611.

33x12.50R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 285/75R17.

Size pages

Other comparisons with 285/75R17

Other comparisons with 33x12.50R18

Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.