265/60R18 vs 275/50R20

275/50R20 is 0.31 in (7.8 mm) taller than 265/60R18, a +1.01% diameter difference. With the speedometer set for 265/60R18, an indicated 60 mph is 60.6 mph on 275/50R20.

Is this a safe swap?

Diameter difference +1.01%: within the ±3% guideline

By overall diameter alone, 275/50R20 falls inside the ±3% range commonly used as a guideline when replacing 265/60R18. 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.

265/60R18 vs 275/50R20 differences
Measurement	265/60R18	275/50R20	Difference	% diff
Overall diameter	30.52 in (775.2 mm)	30.83 in (783.0 mm)	+0.31 in (+7.8 mm)	+1.01%
Sidewall height	6.26 in (159.0 mm)	5.41 in (137.5 mm)	−0.85 in (−21.5 mm)	−13.52%
Section width	10.43 in (265.0 mm)	10.83 in (275.0 mm)	+0.39 in (+10.0 mm)	+3.77%
Circumference	95.88 in (2,435.4 mm)	96.85 in (2,459.9 mm)	+0.96 in (+24.5 mm)	+1.01%
Revolutions per mile	661	654	−7	−1.00%

True speed with the speedometer calibrated for 265/60R18
Indicated	Actual on 265/60R18	Actual on 275/50R20	Difference
30 mph	30.0 mph	30.3 mph	+0.3 mph
60 mph	60.0 mph	60.6 mph	+0.6 mph
75 mph	75.0 mph	75.8 mph	+0.8 mph

Ride-height change: 275/50R20 raises the vehicle by 0.15 in (3.9 mm) at the axle (half the +7.8 mm diameter difference).

275/50R20 is 0.31 in taller than 265/60R18 and 10 mm wider, a 1.01% difference in overall diameter.

With the speedometer calibrated for 265/60R18, an indicated 60 mph is actually 60.6 mph on 275/50R20, and revolutions per mile change from 661 to 654.

275/50R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 265/60R18.

Size pages

Other comparisons with 265/60R18

Other comparisons with 275/50R20

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