My Tire Guide

235/40R18 tire size

A 235/40R18 tire stands 25.4 inches tall and 9.3 inches wide, with a 3.7-inch sidewall on an 18-inch rim.

25.4″OVERALL 25.4 IN · RIM 18 IN9.3″3.7″WIDTH · SIDEWALL
Overall height
25.4 in645 mm
Section width
9.3 in235 mm
Sidewall height
3.7 in94 mm
Rim diameter
18 in457 mm
Circumference
79.8 in2027 mm
Revolutions per mile
794493 per km
Inch size
25.4x9.3R18

Compare it with any other size in the tire size calculator.

Sizes you can swap to

These 18-inch sizes are within two width steps and 3% of a 235/40R18's overall height, the usual limit before the speedometer, ABS and transmission notice. The closest is 215/45R18, 0.9% taller (0.22 in). Wider sizes also need room in the wheel well and a rim width that suits them.

SizeHeightWidthAt 60 mph
215/45R18+0.9%+0.22 in−20 mm60.5 mph
225/40R18−1.2%−0.31 in−10 mm59.3 mph
245/40R18+1.2%+0.31 in+10 mm60.7 mph
255/35R18−1.5%−0.37 in+20 mm59.1 mph
225/45R18+2.2%+0.57 in−10 mm61.3 mph
215/40R18−2.5%−0.63 in−20 mm58.5 mph
255/40R18+2.5%+0.63 in+20 mm61.5 mph
245/35R18−2.6%−0.65 in+10 mm58.5 mph

Plus and minus sizes

Changing rim size means changing the sidewall to keep the same overall height. On 16-inch or 17-inch or 19-inch or 20-inch rims, these are the closest matches to a 235/40R18.

SizeHeightWidthAt 60 mph
265/45R16−0.0%−0.01 in+30 mm60.0 mph
265/40R17−0.2%−0.06 in+30 mm59.9 mph
205/40R19+0.2%+0.06 in−30 mm60.1 mph
205/35R20+1.0%+0.25 in−30 mm60.6 mph

Other 18-inch sizes near 235/40R18

235 mm wide, other sidewalls

40 series, other widths

See the other sizes for this rim on 18-inch tire sizes.

Shop 235/40R18 tires

These open each store's own list of 235/40R18 tires, where you can filter by type, load and speed rating.

235/40R18 questions

How tall is a 235/40R18 tire?

About 25.4 inches (645 mm) from the ground to the top of the tread, unloaded. On the vehicle, carrying weight, it sits a little lower.

What does 235/40R18 mean?

235 is the section width in millimetres (9.3 in). 40 means the sidewall is 40% of that width: 94 mm, or 3.7 in. R means radial construction, and 18 is the rim diameter in inches.

Can I use 215/45R18 instead of 235/40R18?

215/45R18 is 0.9% taller (0.22 in) and 20 mm narrower, which is inside the usual 3% rule. With it fitted, the speedometer shows 60 mph when you are doing 60.5 mph.

What is 235/40R18 in inches?

In inch terms it is 25.4x9.3R18: 25.4 inches tall, 9.3 inches wide, for an 18-inch rim.

How many revolutions per mile does a 235/40R18 make?

About 794 turns per mile, worked out from its unloaded circumference of 79.8 inches. Makers list slightly higher numbers for their own tires, because a loaded tire rolls on a smaller radius.