225/35R20 vs 265/30R20

265/30R20 is 0.06 in (1.5 mm) taller than 225/35R20, a +0.23% diameter difference. With the speedometer set for 225/35R20, an indicated 60 mph is 60.1 mph on 265/30R20.

Is this a safe swap?

Diameter difference +0.23%: under 1%

By overall diameter alone, 265/30R20 is a near match for 225/35R20; 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.

225/35R20 vs 265/30R20 differences
Measurement	225/35R20	265/30R20	Difference	% diff
Overall diameter	26.20 in (665.5 mm)	26.26 in (667.0 mm)	+0.06 in (+1.5 mm)	+0.23%
Sidewall height	3.10 in (78.8 mm)	3.13 in (79.5 mm)	+0.03 in (+0.8 mm)	+0.95%
Section width	8.86 in (225.0 mm)	10.43 in (265.0 mm)	+1.57 in (+40.0 mm)	+17.78%
Circumference	82.31 in (2,090.7 mm)	82.50 in (2,095.4 mm)	+0.19 in (+4.7 mm)	+0.23%
Revolutions per mile	770	768	−2	−0.22%

True speed with the speedometer calibrated for 225/35R20
Indicated	Actual on 225/35R20	Actual on 265/30R20	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.1 mph	+0.1 mph
75 mph	75.0 mph	75.2 mph	+0.2 mph

Ride-height change: 265/30R20 raises the vehicle by 0.03 in (0.8 mm) at the axle (half the +1.5 mm diameter difference).

265/30R20 is 0.06 in taller than 225/35R20 and 40 mm wider, a 0.23% difference in overall diameter.

With the speedometer calibrated for 225/35R20, an indicated 60 mph is actually 60.1 mph on 265/30R20, and revolutions per mile change from 770 to 768.

Both sizes mount on 20-inch wheels.

Size pages

Other comparisons with 225/35R20

Other comparisons with 265/30R20

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