275/65R18 vs 265/60R20

265/60R20 is 0.44 in (11.3 mm) taller than 275/65R18, a +1.39% diameter difference. With the speedometer set for 275/65R18, an indicated 60 mph is 60.8 mph on 265/60R20.

Is this a safe swap?

Diameter difference +1.39%: within the ±3% guideline

By overall diameter alone, 265/60R20 falls inside the ±3% range commonly used as a guideline when replacing 275/65R18. 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.

275/65R18 vs 265/60R20 differences
Measurement	275/65R18	265/60R20	Difference	% diff
Overall diameter	32.07 in (814.7 mm)	32.52 in (826.0 mm)	+0.44 in (+11.3 mm)	+1.39%
Sidewall height	7.04 in (178.8 mm)	6.26 in (159.0 mm)	−0.78 in (−19.7 mm)	−11.05%
Section width	10.83 in (275.0 mm)	10.43 in (265.0 mm)	−0.39 in (−10.0 mm)	−3.64%
Circumference	100.77 in (2,559.5 mm)	102.16 in (2,595.0 mm)	+1.40 in (+35.5 mm)	+1.39%
Revolutions per mile	629	620	−9	−1.37%

True speed with the speedometer calibrated for 275/65R18
Indicated	Actual on 275/65R18	Actual on 265/60R20	Difference
30 mph	30.0 mph	30.4 mph	+0.4 mph
60 mph	60.0 mph	60.8 mph	+0.8 mph
75 mph	75.0 mph	76.0 mph	+1.0 mph

Ride-height change: 265/60R20 raises the vehicle by 0.22 in (5.6 mm) at the axle (half the +11.3 mm diameter difference).

265/60R20 is 0.44 in taller than 275/65R18 and 10 mm narrower, a 1.39% difference in overall diameter.

With the speedometer calibrated for 275/65R18, an indicated 60 mph is actually 60.8 mph on 265/60R20, and revolutions per mile change from 629 to 620.

265/60R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 275/65R18.

Size pages

Other comparisons with 275/65R18

Other comparisons with 265/60R20

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