TireSizesFinder

285/65R18 vs 33x12.50R18

33x12.50R18 is 0.41 in (10.5 mm) taller than 285/65R18, a +1.27% diameter difference. With the speedometer set for 285/65R18, an indicated 60 mph is 60.8 mph on 33x12.50R18.

Is this a safe swap?

Diameter difference +1.27%: within the ±3% guideline

By overall diameter alone, 33x12.50R18 falls inside the ±3% range commonly used as a guideline when replacing 285/65R18. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 285/65R18 (32.59 in) vs 33x12.50R18 (33.00 in)285/65R1832.59 in × 11.22 in33x12.50R1833.00 in × 12.50 in
Side profile and tread width, drawn to the same scale.
285/65R18 vs 33x12.50R18 differences
Measurement285/65R1833x12.50R18Difference% diff
Overall diameter32.59 in (827.7 mm)33.00 in (838.2 mm)+0.41 in (+10.5 mm)+1.27%
Sidewall height7.29 in (185.3 mm)7.50 in (190.5 mm)+0.21 in (+5.3 mm)+2.83%
Section width11.22 in (285.0 mm)12.50 in (317.5 mm)+1.28 in (+32.5 mm)+11.40%
Circumference102.37 in (2,600.3 mm)103.67 in (2,633.3 mm)+1.30 in (+33.0 mm)+1.27%
Revolutions per mile619611−8−1.25%
True speed with the speedometer calibrated for 285/65R18
IndicatedActual on 285/65R18Actual on 33x12.50R18Difference
30 mph30.0 mph30.4 mph+0.4 mph
60 mph60.0 mph60.8 mph+0.8 mph
75 mph75.0 mph76.0 mph+1.0 mph

Ride-height change: 33x12.50R18 raises the vehicle by 0.21 in (5.3 mm) at the axle (half the +10.5 mm diameter difference).

33x12.50R18 is 0.41 in taller than 285/65R18 and 33 mm wider, a 1.27% difference in overall diameter.

With the speedometer calibrated for 285/65R18, an indicated 60 mph is actually 60.8 mph on 33x12.50R18, and revolutions per mile change from 619 to 611.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 285/65R18

Other comparisons with 33x12.50R18

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