265/50R20 vs 245/55R20

245/55R20 is 0.18 in (4.5 mm) taller than 265/50R20, a +0.58% diameter difference. With the speedometer set for 265/50R20, an indicated 60 mph is 60.3 mph on 245/55R20.

Is this a safe swap?

Diameter difference +0.58%: under 1%

By overall diameter alone, 245/55R20 is a near match for 265/50R20; 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.

265/50R20 vs 245/55R20 differences
Measurement	265/50R20	245/55R20	Difference	% diff
Overall diameter	30.43 in (773.0 mm)	30.61 in (777.5 mm)	+0.18 in (+4.5 mm)	+0.58%
Sidewall height	5.22 in (132.5 mm)	5.31 in (134.8 mm)	+0.09 in (+2.3 mm)	+1.70%
Section width	10.43 in (265.0 mm)	9.65 in (245.0 mm)	−0.79 in (−20.0 mm)	−7.55%
Circumference	95.61 in (2,428.5 mm)	96.16 in (2,442.6 mm)	+0.56 in (+14.1 mm)	+0.58%
Revolutions per mile	663	659	−4	−0.58%

True speed with the speedometer calibrated for 265/50R20
Indicated	Actual on 265/50R20	Actual on 245/55R20	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.3 mph	+0.3 mph
75 mph	75.0 mph	75.4 mph	+0.4 mph

Ride-height change: 245/55R20 raises the vehicle by 0.09 in (2.3 mm) at the axle (half the +4.5 mm diameter difference).

245/55R20 is 0.18 in taller than 265/50R20 and 20 mm narrower, a 0.58% difference in overall diameter.

With the speedometer calibrated for 265/50R20, an indicated 60 mph is actually 60.3 mph on 245/55R20, and revolutions per mile change from 663 to 659.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 265/50R20

Other comparisons with 245/55R20

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