255/60R20 vs 275/60R20

275/60R20 is 0.94 in (24.0 mm) taller than 255/60R20, a +2.95% diameter difference. With the speedometer set for 255/60R20, an indicated 60 mph is 61.8 mph on 275/60R20.

Is this a safe swap?

Diameter difference +2.95%: within the ±3% guideline

By overall diameter alone, 275/60R20 falls inside the ±3% range commonly used as a guideline when replacing 255/60R20. 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.

255/60R20 vs 275/60R20 differences
Measurement	255/60R20	275/60R20	Difference	% diff
Overall diameter	32.05 in (814.0 mm)	32.99 in (838.0 mm)	+0.94 in (+24.0 mm)	+2.95%
Sidewall height	6.02 in (153.0 mm)	6.50 in (165.0 mm)	+0.47 in (+12.0 mm)	+7.84%
Section width	10.04 in (255.0 mm)	10.83 in (275.0 mm)	+0.79 in (+20.0 mm)	+7.84%
Circumference	100.68 in (2,557.3 mm)	103.65 in (2,632.7 mm)	+2.97 in (+75.4 mm)	+2.95%
Revolutions per mile	629	611	−18	−2.86%

True speed with the speedometer calibrated for 255/60R20
Indicated	Actual on 255/60R20	Actual on 275/60R20	Difference
30 mph	30.0 mph	30.9 mph	+0.9 mph
60 mph	60.0 mph	61.8 mph	+1.8 mph
75 mph	75.0 mph	77.2 mph	+2.2 mph

Ride-height change: 275/60R20 raises the vehicle by 0.47 in (12.0 mm) at the axle (half the +24.0 mm diameter difference).

275/60R20 is 0.94 in taller than 255/60R20 and 20 mm wider, a 2.95% difference in overall diameter.

With the speedometer calibrated for 255/60R20, an indicated 60 mph is actually 61.8 mph on 275/60R20, and revolutions per mile change from 629 to 611.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 255/60R20

Other comparisons with 275/60R20

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