TireSizesFinder

255/80R17 vs 33x12.50R18

33x12.50R18 is 0.06 in (1.6 mm) shorter than 255/80R17, a −0.19% diameter difference. With the speedometer set for 255/80R17, an indicated 60 mph is 59.9 mph on 33x12.50R18.

Is this a safe swap?

Diameter difference −0.19%: under 1%

By overall diameter alone, 33x12.50R18 is a near match for 255/80R17; the speedometer changes by less than 1%. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 255/80R17 (33.06 in) vs 33x12.50R18 (33.00 in)255/80R1733.06 in × 10.04 in33x12.50R1833.00 in × 12.50 in
Side profile and tread width, drawn to the same scale.
255/80R17 vs 33x12.50R18 differences
Measurement255/80R1733x12.50R18Difference% diff
Overall diameter33.06 in (839.8 mm)33.00 in (838.2 mm)−0.06 in (−1.6 mm)−0.19%
Sidewall height8.03 in (204.0 mm)7.50 in (190.5 mm)−0.53 in (−13.5 mm)−6.62%
Section width10.04 in (255.0 mm)12.50 in (317.5 mm)+2.46 in (+62.5 mm)+24.51%
Circumference103.87 in (2,638.3 mm)103.67 in (2,633.3 mm)−0.20 in (−5.0 mm)−0.19%
Revolutions per mile610611+1+0.19%
True speed with the speedometer calibrated for 255/80R17
IndicatedActual on 255/80R17Actual on 33x12.50R18Difference
30 mph30.0 mph29.9 mph−0.1 mph
60 mph60.0 mph59.9 mph−0.1 mph
75 mph75.0 mph74.9 mph−0.1 mph

Ride-height change: 33x12.50R18 lowers the vehicle by 0.03 in (0.8 mm) at the axle (half the −1.6 mm diameter difference).

33x12.50R18 is 0.06 in shorter than 255/80R17 and 63 mm wider, a 0.19% difference in overall diameter.

With the speedometer calibrated for 255/80R17, an indicated 60 mph is actually 59.9 mph on 33x12.50R18, and revolutions per mile change from 610 to 611.

33x12.50R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 255/80R17.

Size pages

Other comparisons with 255/80R17

Other comparisons with 33x12.50R18

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