255/60R20 vs 33x12.50R20

33x12.50R20 is 0.95 in (24.2 mm) taller than 255/60R20, a +2.97% diameter difference. With the speedometer set for 255/60R20, an indicated 60 mph is 61.8 mph on 33x12.50R20.

Is this a safe swap?

Diameter difference +2.97%: within the ±3% guideline

By overall diameter alone, 33x12.50R20 falls inside the ±3% range commonly used as a guideline when replacing 255/60R20. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

Side profile and tread width, drawn to the same scale.

255/60R20 vs 33x12.50R20 differences
Measurement	255/60R20	33x12.50R20	Difference	% diff
Overall diameter	32.05 in (814.0 mm)	33.00 in (838.2 mm)	+0.95 in (+24.2 mm)	+2.97%
Sidewall height	6.02 in (153.0 mm)	6.50 in (165.1 mm)	+0.48 in (+12.1 mm)	+7.91%
Section width	10.04 in (255.0 mm)	12.50 in (317.5 mm)	+2.46 in (+62.5 mm)	+24.51%
Circumference	100.68 in (2,557.3 mm)	103.67 in (2,633.3 mm)	+2.99 in (+76.0 mm)	+2.97%
Revolutions per mile	629	611	−18	−2.89%

True speed with the speedometer calibrated for 255/60R20
Indicated	Actual on 255/60R20	Actual on 33x12.50R20	Difference
30 mph	30.0 mph	30.9 mph	+0.9 mph
60 mph	60.0 mph	61.8 mph	+1.8 mph
75 mph	75.0 mph	77.2 mph	+2.2 mph

Ride-height change: 33x12.50R20 raises the vehicle by 0.48 in (12.1 mm) at the axle (half the +24.2 mm diameter difference).

33x12.50R20 is 0.95 in taller than 255/60R20 and 63 mm wider, a 2.97% difference in overall diameter.

With the speedometer calibrated for 255/60R20, an indicated 60 mph is actually 61.8 mph on 33x12.50R20, and revolutions per mile change from 629 to 611.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 255/60R20

Other comparisons with 33x12.50R20

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.