265/30R20 vs 235/35R20

235/35R20 is 0.22 in (5.5 mm) taller than 265/30R20, a +0.82% diameter difference. With the speedometer set for 265/30R20, an indicated 60 mph is 60.5 mph on 235/35R20.

Is this a safe swap?

Diameter difference +0.82%: under 1%

By overall diameter alone, 235/35R20 is a near match for 265/30R20; 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.

265/30R20 vs 235/35R20 differences
Measurement	265/30R20	235/35R20	Difference	% diff
Overall diameter	26.26 in (667.0 mm)	26.48 in (672.5 mm)	+0.22 in (+5.5 mm)	+0.82%
Sidewall height	3.13 in (79.5 mm)	3.24 in (82.3 mm)	+0.11 in (+2.8 mm)	+3.46%
Section width	10.43 in (265.0 mm)	9.25 in (235.0 mm)	−1.18 in (−30.0 mm)	−11.32%
Circumference	82.50 in (2,095.4 mm)	83.18 in (2,112.7 mm)	+0.68 in (+17.3 mm)	+0.82%
Revolutions per mile	768	762	−6	−0.82%

True speed with the speedometer calibrated for 265/30R20
Indicated	Actual on 265/30R20	Actual on 235/35R20	Difference
30 mph	30.0 mph	30.2 mph	+0.2 mph
60 mph	60.0 mph	60.5 mph	+0.5 mph
75 mph	75.0 mph	75.6 mph	+0.6 mph

Ride-height change: 235/35R20 raises the vehicle by 0.11 in (2.8 mm) at the axle (half the +5.5 mm diameter difference).

235/35R20 is 0.22 in taller than 265/30R20 and 30 mm narrower, a 0.82% difference in overall diameter.

With the speedometer calibrated for 265/30R20, an indicated 60 mph is actually 60.5 mph on 235/35R20, and revolutions per mile change from 768 to 762.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 265/30R20

Other comparisons with 235/35R20

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