235/55R20 vs 265/50R20

265/50R20 is 0.26 in (6.5 mm) taller than 235/55R20, a +0.85% diameter difference. With the speedometer set for 235/55R20, an indicated 60 mph is 60.5 mph on 265/50R20.

Is this a safe swap?

Diameter difference +0.85%: under 1%

By overall diameter alone, 265/50R20 is a near match for 235/55R20; 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.

235/55R20 vs 265/50R20 differences
Measurement	235/55R20	265/50R20	Difference	% diff
Overall diameter	30.18 in (766.5 mm)	30.43 in (773.0 mm)	+0.26 in (+6.5 mm)	+0.85%
Sidewall height	5.09 in (129.3 mm)	5.22 in (132.5 mm)	+0.13 in (+3.3 mm)	+2.51%
Section width	9.25 in (235.0 mm)	10.43 in (265.0 mm)	+1.18 in (+30.0 mm)	+12.77%
Circumference	94.80 in (2,408.0 mm)	95.61 in (2,428.5 mm)	+0.80 in (+20.4 mm)	+0.85%
Revolutions per mile	668	663	−6	−0.84%

True speed with the speedometer calibrated for 235/55R20
Indicated	Actual on 235/55R20	Actual on 265/50R20	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.5 mph	+0.5 mph
75 mph	75.0 mph	75.6 mph	+0.6 mph

Ride-height change: 265/50R20 raises the vehicle by 0.13 in (3.3 mm) at the axle (half the +6.5 mm diameter difference).

265/50R20 is 0.26 in taller than 235/55R20 and 30 mm wider, a 0.85% difference in overall diameter.

With the speedometer calibrated for 235/55R20, an indicated 60 mph is actually 60.5 mph on 265/50R20, and revolutions per mile change from 668 to 663.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 235/55R20

Other comparisons with 265/50R20

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