255/45R17 vs 295/35R18

295/35R18 is 0.09 in (2.4 mm) taller than 255/45R17, a +0.36% diameter difference. With the speedometer set for 255/45R17, an indicated 60 mph is 60.2 mph on 295/35R18.

Is this a safe swap?

Diameter difference +0.36%: under 1%

By overall diameter alone, 295/35R18 is a near match for 255/45R17; 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.

255/45R17 vs 295/35R18 differences
Measurement	255/45R17	295/35R18	Difference	% diff
Overall diameter	26.04 in (661.3 mm)	26.13 in (663.7 mm)	+0.09 in (+2.4 mm)	+0.36%
Sidewall height	4.52 in (114.8 mm)	4.06 in (103.3 mm)	−0.45 in (−11.5 mm)	−10.02%
Section width	10.04 in (255.0 mm)	11.61 in (295.0 mm)	+1.57 in (+40.0 mm)	+15.69%
Circumference	81.79 in (2,077.5 mm)	82.09 in (2,085.1 mm)	+0.30 in (+7.5 mm)	+0.36%
Revolutions per mile	775	772	−3	−0.36%

True speed with the speedometer calibrated for 255/45R17
Indicated	Actual on 255/45R17	Actual on 295/35R18	Difference
30 mph	30.0 mph	30.1 mph	+0.1 mph
60 mph	60.0 mph	60.2 mph	+0.2 mph
75 mph	75.0 mph	75.3 mph	+0.3 mph

Ride-height change: 295/35R18 raises the vehicle by 0.05 in (1.2 mm) at the axle (half the +2.4 mm diameter difference).

295/35R18 is 0.09 in taller than 255/45R17 and 40 mm wider, a 0.36% difference in overall diameter.

With the speedometer calibrated for 255/45R17, an indicated 60 mph is actually 60.2 mph on 295/35R18, and revolutions per mile change from 775 to 772.

295/35R18 mounts on a 18-inch wheel, a plus-1 fitment from the 17-inch wheel of 255/45R17.

Size pages

Other comparisons with 255/45R17

Other comparisons with 295/35R18

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