265/50R19 vs 265/45R20

265/45R20 is 0.04 in (1.1 mm) shorter than 265/50R19, a −0.15% diameter difference. With the speedometer set for 265/50R19, an indicated 60 mph is 59.9 mph on 265/45R20.

Is this a safe swap?

Diameter difference −0.15%: under 1%

By overall diameter alone, 265/45R20 is a near match for 265/50R19; 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.

265/50R19 vs 265/45R20 differences
Measurement	265/50R19	265/45R20	Difference	% diff
Overall diameter	29.43 in (747.6 mm)	29.39 in (746.5 mm)	−0.04 in (−1.1 mm)	−0.15%
Sidewall height	5.22 in (132.5 mm)	4.69 in (119.3 mm)	−0.52 in (−13.2 mm)	−10.00%
Section width	10.43 in (265.0 mm)	10.43 in (265.0 mm)	0.00 in (0.0 mm)	0.00%
Circumference	92.47 in (2,348.7 mm)	92.33 in (2,345.2 mm)	−0.14 in (−3.5 mm)	−0.15%
Revolutions per mile	685	686	+1	+0.15%

True speed with the speedometer calibrated for 265/50R19
Indicated	Actual on 265/50R19	Actual on 265/45R20	Difference
30 mph	30.0 mph	30.0 mph	0.0 mph
60 mph	60.0 mph	59.9 mph	−0.1 mph
75 mph	75.0 mph	74.9 mph	−0.1 mph

Ride-height change: 265/45R20 lowers the vehicle by 0.02 in (0.5 mm) at the axle (half the −1.1 mm diameter difference).

265/45R20 is 0.04 in shorter than 265/50R19 and the same width, a 0.15% difference in overall diameter.

With the speedometer calibrated for 265/50R19, an indicated 60 mph is actually 59.9 mph on 265/45R20, and revolutions per mile change from 685 to 686.

265/45R20 mounts on a 20-inch wheel, a plus-1 fitment from the 19-inch wheel of 265/50R19.

Size pages

Other comparisons with 265/50R19

Other comparisons with 265/45R20

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