255/50R18 vs 295/35R20

295/35R20 is 0.09 in (2.3 mm) taller than 255/50R18, a +0.32% diameter difference. With the speedometer set for 255/50R18, an indicated 60 mph is 60.2 mph on 295/35R20.

Is this a safe swap?

Diameter difference +0.32%: under 1%

By overall diameter alone, 295/35R20 is a near match for 255/50R18; the speedometer changes by less than 1%. 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.

255/50R18 vs 295/35R20 differences
Measurement	255/50R18	295/35R20	Difference	% diff
Overall diameter	28.04 in (712.2 mm)	28.13 in (714.5 mm)	+0.09 in (+2.3 mm)	+0.32%
Sidewall height	5.02 in (127.5 mm)	4.06 in (103.3 mm)	−0.95 in (−24.2 mm)	−19.02%
Section width	10.04 in (255.0 mm)	11.61 in (295.0 mm)	+1.57 in (+40.0 mm)	+15.69%
Circumference	88.09 in (2,237.4 mm)	88.37 in (2,244.7 mm)	+0.28 in (+7.2 mm)	+0.32%
Revolutions per mile	719	717	−2	−0.32%

True speed with the speedometer calibrated for 255/50R18
Indicated	Actual on 255/50R18	Actual on 295/35R20	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.2 mph	+0.2 mph

Ride-height change: 295/35R20 raises the vehicle by 0.05 in (1.1 mm) at the axle (half the +2.3 mm diameter difference).

295/35R20 is 0.09 in taller than 255/50R18 and 40 mm wider, a 0.32% difference in overall diameter.

With the speedometer calibrated for 255/50R18, an indicated 60 mph is actually 60.2 mph on 295/35R20, and revolutions per mile change from 719 to 717.

295/35R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 255/50R18.

Size pages

Other comparisons with 255/50R18

Other comparisons with 295/35R20

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