265/55R20 vs 255/60R20

255/60R20 is 0.57 in (14.5 mm) taller than 265/55R20, a +1.81% diameter difference. With the speedometer set for 265/55R20, an indicated 60 mph is 61.1 mph on 255/60R20.

Is this a safe swap?

Diameter difference +1.81%: within the ±3% guideline

By overall diameter alone, 255/60R20 falls inside the ±3% range commonly used as a guideline when replacing 265/55R20. 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.

265/55R20 vs 255/60R20 differences
Measurement	265/55R20	255/60R20	Difference	% diff
Overall diameter	31.48 in (799.5 mm)	32.05 in (814.0 mm)	+0.57 in (+14.5 mm)	+1.81%
Sidewall height	5.74 in (145.8 mm)	6.02 in (153.0 mm)	+0.29 in (+7.3 mm)	+4.97%
Section width	10.43 in (265.0 mm)	10.04 in (255.0 mm)	−0.39 in (−10.0 mm)	−3.77%
Circumference	98.89 in (2,511.7 mm)	100.68 in (2,557.3 mm)	+1.79 in (+45.6 mm)	+1.81%
Revolutions per mile	641	629	−11	−1.78%

True speed with the speedometer calibrated for 265/55R20
Indicated	Actual on 265/55R20	Actual on 255/60R20	Difference
30 mph	30.0 mph	30.5 mph	+0.5 mph
60 mph	60.0 mph	61.1 mph	+1.1 mph
75 mph	75.0 mph	76.4 mph	+1.4 mph

Ride-height change: 255/60R20 raises the vehicle by 0.29 in (7.3 mm) at the axle (half the +14.5 mm diameter difference).

255/60R20 is 0.57 in taller than 265/55R20 and 10 mm narrower, a 1.81% difference in overall diameter.

With the speedometer calibrated for 265/55R20, an indicated 60 mph is actually 61.1 mph on 255/60R20, and revolutions per mile change from 641 to 629.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 265/55R20

Other comparisons with 255/60R20

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