255/50R20 vs 275/50R20

275/50R20 is 0.79 in (20.0 mm) taller than 255/50R20, a +2.62% diameter difference. With the speedometer set for 255/50R20, an indicated 60 mph is 61.6 mph on 275/50R20.

Is this a safe swap?

Diameter difference +2.62%: within the ±3% guideline

By overall diameter alone, 275/50R20 falls inside the ±3% range commonly used as a guideline when replacing 255/50R20. 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.

255/50R20 vs 275/50R20 differences
Measurement	255/50R20	275/50R20	Difference	% diff
Overall diameter	30.04 in (763.0 mm)	30.83 in (783.0 mm)	+0.79 in (+20.0 mm)	+2.62%
Sidewall height	5.02 in (127.5 mm)	5.41 in (137.5 mm)	+0.39 in (+10.0 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	94.37 in (2,397.0 mm)	96.85 in (2,459.9 mm)	+2.47 in (+62.8 mm)	+2.62%
Revolutions per mile	671	654	−17	−2.55%

True speed with the speedometer calibrated for 255/50R20
Indicated	Actual on 255/50R20	Actual on 275/50R20	Difference
30 mph	30.0 mph	30.8 mph	+0.8 mph
60 mph	60.0 mph	61.6 mph	+1.6 mph
75 mph	75.0 mph	77.0 mph	+2.0 mph

Ride-height change: 275/50R20 raises the vehicle by 0.39 in (10.0 mm) at the axle (half the +20.0 mm diameter difference).

275/50R20 is 0.79 in taller than 255/50R20 and 20 mm wider, a 2.62% difference in overall diameter.

With the speedometer calibrated for 255/50R20, an indicated 60 mph is actually 61.6 mph on 275/50R20, and revolutions per mile change from 671 to 654.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 255/50R20

Other comparisons with 275/50R20

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