My Tire Guide

255/40R18 tire size

A 255/40R18 tire stands 26.0 inches tall and 10.0 inches wide, with a 4.0-inch sidewall on an 18-inch rim.

26.0″OVERALL 26.0 IN · RIM 18 IN10.0″4.0″WIDTH · SIDEWALL
Overall height
26.0 in661 mm
Section width
10.0 in255 mm
Sidewall height
4.0 in102 mm
Rim diameter
18 in457 mm
Circumference
81.8 in2077 mm
Revolutions per mile
775481 per km
Inch size
26.0x10.0R18

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 255/40R18's overall height, the usual limit before the speedometer, ABS and transmission notice. The closest is 235/45R18, 1.1% taller (0.30 in). Wider sizes also need room in the wheel well and a rim width that suits them.

SizeHeightWidthAt 60 mph
235/45R18+1.1%+0.30 in−20 mm60.7 mph
265/40R18+1.2%+0.31 in+10 mm60.7 mph
245/40R18−1.2%−0.31 in−10 mm59.3 mph
275/35R18−1.7%−0.45 in+20 mm59.0 mph
235/40R18−2.4%−0.63 in−20 mm58.5 mph
275/40R18+2.4%+0.63 in+20 mm61.5 mph
245/45R18+2.5%+0.65 in−10 mm61.5 mph
265/35R18−2.8%−0.73 in+10 mm58.3 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 255/40R18.

SizeHeightWidthAt 60 mph
255/50R16+0.0%+0.01 in±0 mm60.0 mph
255/45R17+0.0%+0.00 in±0 mm60.0 mph
255/35R19−0.0%−0.00 in±0 mm60.0 mph
225/35R20+0.7%+0.17 in−30 mm60.4 mph

Other 18-inch sizes near 255/40R18

255 mm wide, other sidewalls

40 series, other widths

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

Shop 255/40R18 tires

These open each store's own list of 255/40R18 tires, where you can filter by type, load and speed rating.

255/40R18 questions

How tall is a 255/40R18 tire?

About 26.0 inches (661 mm) from the ground to the top of the tread, unloaded. On the vehicle, carrying weight, it sits a little lower.

What does 255/40R18 mean?

255 is the section width in millimetres (10.0 in). 40 means the sidewall is 40% of that width: 102 mm, or 4.0 in. R means radial construction, and 18 is the rim diameter in inches.

Can I use 235/45R18 instead of 255/40R18?

235/45R18 is 1.1% taller (0.30 in) and 20 mm narrower, which is inside the usual 3% rule. With it fitted, the speedometer shows 60 mph when you are doing 60.7 mph.

What is 255/40R18 in inches?

In inch terms it is 26.0x10.0R18: 26.0 inches tall, 10.0 inches wide, for an 18-inch rim.

How many revolutions per mile does a 255/40R18 make?

About 775 turns per mile, worked out from its unloaded circumference of 81.8 inches. Makers list slightly higher numbers for their own tires, because a loaded tire rolls on a smaller radius.