295/30R19 vs 255/30R20

255/30R20 is 0.06 in (1.4 mm) taller than 295/30R19, a +0.21% diameter difference. With the speedometer set for 295/30R19, an indicated 60 mph is 60.1 mph on 255/30R20.

Is this a safe swap?

Diameter difference +0.21%: under 1%

By overall diameter alone, 255/30R20 is a near match for 295/30R19; 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.

295/30R19 vs 255/30R20 differences
Measurement	295/30R19	255/30R20	Difference	% diff
Overall diameter	25.97 in (659.6 mm)	26.02 in (661.0 mm)	+0.06 in (+1.4 mm)	+0.21%
Sidewall height	3.48 in (88.5 mm)	3.01 in (76.5 mm)	−0.47 in (−12.0 mm)	−13.56%
Section width	11.61 in (295.0 mm)	10.04 in (255.0 mm)	−1.57 in (−40.0 mm)	−13.56%
Circumference	81.58 in (2,072.2 mm)	81.76 in (2,076.6 mm)	+0.17 in (+4.4 mm)	+0.21%
Revolutions per mile	777	775	−2	−0.21%

True speed with the speedometer calibrated for 295/30R19
Indicated	Actual on 295/30R19	Actual on 255/30R20	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.1 mph	+0.1 mph
75 mph	75.0 mph	75.2 mph	+0.2 mph

Ride-height change: 255/30R20 raises the vehicle by 0.03 in (0.7 mm) at the axle (half the +1.4 mm diameter difference).

255/30R20 is 0.06 in taller than 295/30R19 and 40 mm narrower, a 0.21% difference in overall diameter.

With the speedometer calibrated for 295/30R19, an indicated 60 mph is actually 60.1 mph on 255/30R20, and revolutions per mile change from 777 to 775.

255/30R20 mounts on a 20-inch wheel, a plus-1 fitment from the 19-inch wheel of 295/30R19.

Size pages

Other comparisons with 295/30R19

Other comparisons with 255/30R20

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