235/45R17 vs 265/40R17

265/40R17 is 0.02 in (0.5 mm) taller than 235/45R17, a +0.08% diameter difference. With the speedometer set for 235/45R17, an indicated 60 mph is 60.0 mph on 265/40R17.

Is this a safe swap?

Diameter difference +0.08%: under 1%

By overall diameter alone, 265/40R17 is a near match for 235/45R17; 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.

235/45R17 vs 265/40R17 differences
Measurement	235/45R17	265/40R17	Difference	% diff
Overall diameter	25.33 in (643.3 mm)	25.35 in (643.8 mm)	+0.02 in (+0.5 mm)	+0.08%
Sidewall height	4.16 in (105.8 mm)	4.17 in (106.0 mm)	+0.01 in (+0.3 mm)	+0.24%
Section width	9.25 in (235.0 mm)	10.43 in (265.0 mm)	+1.18 in (+30.0 mm)	+12.77%
Circumference	79.57 in (2,021.0 mm)	79.63 in (2,022.6 mm)	+0.06 in (+1.6 mm)	+0.08%
Revolutions per mile	796	796	−1	−0.08%

True speed with the speedometer calibrated for 235/45R17
Indicated	Actual on 235/45R17	Actual on 265/40R17	Difference
30 mph	30.0 mph	30.0 mph	0.0 mph
60 mph	60.0 mph	60.0 mph	0.0 mph
75 mph	75.0 mph	75.1 mph	+0.1 mph

Ride-height change: 265/40R17 raises the vehicle by 0.01 in (0.3 mm) at the axle (half the +0.5 mm diameter difference).

265/40R17 is 0.02 in taller than 235/45R17 and 30 mm wider, a 0.08% difference in overall diameter.

With the speedometer calibrated for 235/45R17, an indicated 60 mph is actually 60.0 mph on 265/40R17, and revolutions per mile change from 796 to 796.

Both sizes mount on 17-inch wheels.

Size pages

Other comparisons with 235/45R17

Other comparisons with 265/40R17

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