295/70R18 vs 35x12.50R20

35x12.50R20 is 0.74 in (18.8 mm) taller than 295/70R18, a +2.16% diameter difference. With the speedometer set for 295/70R18, an indicated 60 mph is 61.3 mph on 35x12.50R20.

Is this a safe swap?

Diameter difference +2.16%: within the ±3% guideline

By overall diameter alone, 35x12.50R20 falls inside the ±3% range commonly used as a guideline when replacing 295/70R18. 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.

295/70R18 vs 35x12.50R20 differences
Measurement	295/70R18	35x12.50R20	Difference	% diff
Overall diameter	34.26 in (870.2 mm)	35.00 in (889.0 mm)	+0.74 in (+18.8 mm)	+2.16%
Sidewall height	8.13 in (206.5 mm)	7.50 in (190.5 mm)	−0.63 in (−16.0 mm)	−7.75%
Section width	11.61 in (295.0 mm)	12.50 in (317.5 mm)	+0.89 in (+22.5 mm)	+7.63%
Circumference	107.63 in (2,733.8 mm)	109.96 in (2,792.9 mm)	+2.33 in (+59.1 mm)	+2.16%
Revolutions per mile	589	576	−12	−2.11%

True speed with the speedometer calibrated for 295/70R18
Indicated	Actual on 295/70R18	Actual on 35x12.50R20	Difference
30 mph	30.0 mph	30.6 mph	+0.6 mph
60 mph	60.0 mph	61.3 mph	+1.3 mph
75 mph	75.0 mph	76.6 mph	+1.6 mph

Ride-height change: 35x12.50R20 raises the vehicle by 0.37 in (9.4 mm) at the axle (half the +18.8 mm diameter difference).

35x12.50R20 is 0.74 in taller than 295/70R18 and 23 mm wider, a 2.16% difference in overall diameter.

With the speedometer calibrated for 295/70R18, an indicated 60 mph is actually 61.3 mph on 35x12.50R20, and revolutions per mile change from 589 to 576.

35x12.50R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 295/70R18.

Size pages

Other comparisons with 295/70R18

Other comparisons with 35x12.50R20

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