245/45R20 vs 265/45R20

265/45R20 is 0.71 in (18.0 mm) taller than 245/45R20, a +2.47% diameter difference. With the speedometer set for 245/45R20, an indicated 60 mph is 61.5 mph on 265/45R20.

Is this a safe swap?

Diameter difference +2.47%: within the ±3% guideline

By overall diameter alone, 265/45R20 falls inside the ±3% range commonly used as a guideline when replacing 245/45R20. 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.

245/45R20 vs 265/45R20 differences
Measurement	245/45R20	265/45R20	Difference	% diff
Overall diameter	28.68 in (728.5 mm)	29.39 in (746.5 mm)	+0.71 in (+18.0 mm)	+2.47%
Sidewall height	4.34 in (110.3 mm)	4.69 in (119.3 mm)	+0.35 in (+9.0 mm)	+8.16%
Section width	9.65 in (245.0 mm)	10.43 in (265.0 mm)	+0.79 in (+20.0 mm)	+8.16%
Circumference	90.10 in (2,288.7 mm)	92.33 in (2,345.2 mm)	+2.23 in (+56.5 mm)	+2.47%
Revolutions per mile	703	686	−17	−2.41%

True speed with the speedometer calibrated for 245/45R20
Indicated	Actual on 245/45R20	Actual on 265/45R20	Difference
30 mph	30.0 mph	30.7 mph	+0.7 mph
60 mph	60.0 mph	61.5 mph	+1.5 mph
75 mph	75.0 mph	76.9 mph	+1.9 mph

Ride-height change: 265/45R20 raises the vehicle by 0.35 in (9.0 mm) at the axle (half the +18.0 mm diameter difference).

265/45R20 is 0.71 in taller than 245/45R20 and 20 mm wider, a 2.47% difference in overall diameter.

With the speedometer calibrated for 245/45R20, an indicated 60 mph is actually 61.5 mph on 265/45R20, and revolutions per mile change from 703 to 686.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 245/45R20

Other comparisons with 265/45R20

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