265/45R18 vs 265/35R20

265/35R20 is 0.09 in (2.2 mm) shorter than 265/45R18, a −0.32% diameter difference. With the speedometer set for 265/45R18, an indicated 60 mph is 59.8 mph on 265/35R20.

Is this a safe swap?

Diameter difference −0.32%: under 1%

By overall diameter alone, 265/35R20 is a near match for 265/45R18; the speedometer changes by less than 1%. 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.

265/45R18 vs 265/35R20 differences
Measurement	265/45R18	265/35R20	Difference	% diff
Overall diameter	27.39 in (695.7 mm)	27.30 in (693.5 mm)	−0.09 in (−2.2 mm)	−0.32%
Sidewall height	4.69 in (119.3 mm)	3.65 in (92.8 mm)	−1.04 in (−26.5 mm)	−22.22%
Section width	10.43 in (265.0 mm)	10.43 in (265.0 mm)	0.00 in (0.0 mm)	0.00%
Circumference	86.05 in (2,185.6 mm)	85.78 in (2,178.7 mm)	−0.27 in (−6.9 mm)	−0.32%
Revolutions per mile	736	739	+2	+0.32%

True speed with the speedometer calibrated for 265/45R18
Indicated	Actual on 265/45R18	Actual on 265/35R20	Difference
30 mph	30.0 mph	29.9 mph	−0.1 mph
60 mph	60.0 mph	59.8 mph	−0.2 mph
75 mph	75.0 mph	74.8 mph	−0.2 mph

Ride-height change: 265/35R20 lowers the vehicle by 0.04 in (1.1 mm) at the axle (half the −2.2 mm diameter difference).

265/35R20 is 0.09 in shorter than 265/45R18 and the same width, a 0.32% difference in overall diameter.

With the speedometer calibrated for 265/45R18, an indicated 60 mph is actually 59.8 mph on 265/35R20, and revolutions per mile change from 736 to 739.

265/35R20 mounts on a 20-inch wheel, a plus-2 fitment from the 18-inch wheel of 265/45R18.

Size pages

Other comparisons with 265/45R18

Other comparisons with 265/35R20

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