295/35R18 vs 235/45R18

235/45R18 is 0.20 in (5.0 mm) taller than 295/35R18, a +0.75% diameter difference. With the speedometer set for 295/35R18, an indicated 60 mph is 60.5 mph on 235/45R18.

Is this a safe swap?

Diameter difference +0.75%: under 1%

By overall diameter alone, 235/45R18 is a near match for 295/35R18; 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.

295/35R18 vs 235/45R18 differences
Measurement	295/35R18	235/45R18	Difference	% diff
Overall diameter	26.13 in (663.7 mm)	26.33 in (668.7 mm)	+0.20 in (+5.0 mm)	+0.75%
Sidewall height	4.06 in (103.3 mm)	4.16 in (105.8 mm)	+0.10 in (+2.5 mm)	+2.42%
Section width	11.61 in (295.0 mm)	9.25 in (235.0 mm)	−2.36 in (−60.0 mm)	−20.34%
Circumference	82.09 in (2,085.1 mm)	82.71 in (2,100.8 mm)	+0.62 in (+15.7 mm)	+0.75%
Revolutions per mile	772	766	−6	−0.75%

True speed with the speedometer calibrated for 295/35R18
Indicated	Actual on 295/35R18	Actual on 235/45R18	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: 235/45R18 raises the vehicle by 0.10 in (2.5 mm) at the axle (half the +5.0 mm diameter difference).

235/45R18 is 0.20 in taller than 295/35R18 and 60 mm narrower, a 0.75% difference in overall diameter.

With the speedometer calibrated for 295/35R18, an indicated 60 mph is actually 60.5 mph on 235/45R18, and revolutions per mile change from 772 to 766.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 295/35R18

Other comparisons with 235/45R18

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