tireheight.com

235/40R18 in inches

A 235/40R18 tire is 25.4″ tall and 9.3″ wide, and fits a 18″ wheel. In inches it is written 25.4×9.3R18.

Diameter25.40″
Width9.25″
Sidewall3.70″
235/40R18 drawn to scale: 25.40 inch diameter, 3.70 inch sidewall, 18 inch wheel, 9.25 inch tread width18″ wheel3.70″25.40″ overall9.25″ wideSide view
Drawn to scale. Nominal dimensions calculated from the size code.
Manufacturer data

How tall 235/40R18 tires really are

Heights published by BFGoodrich, General, Michelin and Toyo for all 23 tires in this size. Their published revolutions per mile work out to 24.6–24.7″ under load (below).

Real 235/40R18 tires measure 25.39–25.50″, against 25.40″ from the size code. They run both taller and shorter than the size code.

Height under load24.6–24.7″

Published revs per mile (815–819) mean the tire rolls like a 24.6–24.7″ tire on the vehicle. Use this for speedometer calibration.

Weight spread21.4–26.6 lb

The lightest (General G-MAX RS, XL) is 5.2 lb lighter per corner than the heaviest (BFGoodrich g-Force COMP-2 A/S PLUS, XL).

23 tires in 235/40R18

Sort by the spec you care about.

LoadRevs/miSource
General G-MAX RSPerformanceXL · 95Y25.4021.410.01,521818Spec page
Michelin Pilot Sport Cup 2 ConnectPerformanceXL · 95(Y)25.4021.47.21,521819Spec page
Michelin Pilot Alpin 5WinterXL · 95V25.3921.79.51,521819Spec page
Michelin Pilot Sport 4PerformanceXL · 95(Y)25.4022.19.01,521819Spec page
Michelin X-Ice SnowWinterXL · 95H25.3922.310.51,521819Spec page
Michelin Pilot Sport PS2PerformanceXL · 95(Y)25.4022.48.51,521819Spec page
Michelin Pilot Sport 4PerformanceXL · 95(Y)25.4022.69.51,521819Spec page
Michelin Pilot Sport 5PerformanceXL · 95(Y)25.4022.69.01,521819Spec page
Toyo Proxes Sport A/SPerformanceXL · 95Y25.3922.89.31,521818Spec page
General G-MAX AS07PerformanceXL · 95W25.4022.810.01,521818Spec page
Toyo Proxes Sport 2PerformanceXL · 95(Y)25.4022.89.11,521818Spec page
Michelin Pilot Sport 4 SPerformanceXL · 95(Y)25.4022.99.51,521819Spec page
BFGoodrich Advantage ControlAll-seasonXL · 95W25.3923.810.51,521819Spec page
Toyo Extensa HP IIPerformanceXL · 95W25.3924.09.41,521818Spec page
Toyo Celsius IITouringXL · 95V25.3924.111.21,521818Spec page
General AltiMAX Arctic XWinterXL · 95T25.4024.212.01,521818Spec page
Michelin CrossClimate2All-seasonXL · 95V25.4024.910.01,521819Spec page
Toyo Celsius SportPerformanceXL · 95Y25.4024.99.31,521818Spec page
Michelin Pilot Sport All-Season 4PerformanceXL · 95Y25.5025.010.01,521815Spec page
Toyo Observe G3-IceWinterXL · 95T25.3925.111.31,521818Spec page
Toyo Proxes R888RPerformanceXL · 95Y25.3925.46.31,521818Spec page
BFGoodrich g-Force Phenom T/APerformanceXL · 95Y25.3925.49.01,521819Spec page
BFGoodrich g-Force COMP-2 A/S PLUSPerformanceXL · 95W25.3926.69.01,521819Spec page

Is 235/40R18 a 25-inch tire?

≈25″

Close. The size code works out to 25.40″, and the 23 tires here publish 25.39–25.50″, so people call it a 25.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

SizeDiameter ″vs 235/40R18Difference
295/30R1824.97-0.43″-1.7%
255/35R1825.03-0.37″-1.5%
225/40R1825.09-0.31″-1.2%
265/35R1825.30-0.10″-0.4%
315/30R1825.44+0.04″+0.2%
275/35R1825.58+0.18″+0.7%
215/45R1825.62+0.22″+0.9%
245/40R1825.72+0.31″+1.2%
285/35R1825.85+0.45″+1.8%
335/30R1825.91+0.51″+2.0%

How to read 235/40R18

How to read any tire size

235/40R18 95Y as printed on the tire sidewall, with each part numbered235/40R18 95Y123456
How 235/40R18 95Y is printed on the sidewall. It's the most common code among the 23 tires here (7 of them); tires in this size come in other load and speed ratings too.
1235Section width

235 mm across the widest point, or 9.25 inches. Every 235 size

240Aspect ratio

A percentage, not a measurement: the sidewall is 40% as tall as the tire is wide, which is 94.0 mm or 3.70 inches.

3RConstruction

Radial construction.

418Wheel diameter

Mounts on a 18-inch wheel. Approved wheel widths run 8.0″ to 9.5″.

595Load index

Each tire carries up to 1,521 lb (690 kg) at its maximum pressure.

6YSpeed rating

Rated for up to 186 mph sustained.

XLExtra load

Printed after the size.

SpecificationInchesMetric
Overall diameter25.40645 mm
Section width9.25235 mm
Sidewall height3.7094.0 mm
Circumference79.82,027 mm
Revolutions per mile (calculated, unloaded)794.0493 per km
Revolutions per mile (published by manufacturers)815–819506–509 per km
Approved wheel width8.0–9.5203–241 mm

Speedometer error after switching to 235/40R18

Your actual speed– mph

Questions about 235/40R18

What is 235/40R18 in inches?

25.40 inches tall, 9.25 inches wide, on a 18-inch wheel. Written in inches, that is roughly 25.4×9.3R18.

How much does a 235/40R18 tire weigh?

Between 21.4 lb and 26.6 lb for the 23 tires listed here. The lightest is the General G-MAX RS (XL); the heaviest is the BFGoodrich g-Force COMP-2 A/S PLUS (XL).

What wheel width do I need for 235/40R18?

Manufacturers approve 8.0–9.5″ wide wheels for this size.

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

Published figures run 815–819 revolutions per mile. The calculated figure is 794.0, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 235/40R18 than 265/35R18?

0.10 inches taller on paper (25.40″ vs 25.30″), which raises the axle about 0.05″. Your speedometer will read about 0.4% slow.