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345/35R18 in inches

A 345/35R18 tire is 27.5″ tall and 13.6″ wide, and fits a 18″ wheel. In inches it is written 27.5×13.6R18.

Diameter27.51″
Width13.58″
Sidewall4.75″
345/35R18 drawn to scale: 27.51 inch diameter, 4.75 inch sidewall, 18 inch wheel, 13.58 inch tread width18″ wheel4.75″27.51″ overall13.58″ wideSide view
Drawn to scale. Nominal dimensions calculated from the size code.
Manufacturer data

How tall 345/35R18 tires really are

Heights published by Toyo for all 2 tires in this size. Their published revolutions per mile work out to 26.7″ under load (below).

Real 345/35R18 tires measure 27.52–27.52″, against 27.51″ from the size code. They run both taller and shorter than the size code.

Height under load26.7″

Published revs per mile (755) mean the tire rolls like a 26.7″ tire on the vehicle. Use this for speedometer calibration.

Weight spread31.6–35.1 lb

The lightest (Toyo Proxes R, SL) is 3.5 lb lighter per corner than the heaviest (Toyo Proxes RR, SL).

2 tires in 345/35R18

Sort by the spec you care about.

LoadRevs/miSource
Toyo Proxes RPerformanceSL · 109W27.5231.63.62,271755Spec page
Toyo Proxes RRPerformanceSL27.5235.13.62,271755Spec page

Is 345/35R18 a 28-inch tire?

≈28″

Close. The size code works out to 27.51″, and the 2 tires here publish 27.52″, so people call it a 28.

All 28-inch tire sizes, on every wheel size.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

SizeDiameter ″vs 345/35R18Difference
245/45R1826.68-0.83″-3.0%
225/50R1826.86-0.65″-2.4%
285/40R1826.98-0.53″-1.9%
255/45R1827.04-0.47″-1.7%
235/50R1827.25-0.26″-0.9%
215/55R1827.31-0.20″-0.7%
265/45R1827.39-0.12″-0.4%
245/50R1827.65+0.14″+0.5%
225/55R1827.74+0.24″+0.9%
235/55R1828.18+0.67″+2.4%

How to read 345/35R18

How to read any tire size

345/35R18 109W as printed on the tire sidewall, with each part numbered345/35R18 109W123456
How 345/35R18 109W is printed on the sidewall. It's the most common code among the 2 tires here (1 of them); tires in this size come in other load and speed ratings too.
1345Section width

345 mm across the widest point, or 13.58 inches. Every 345 size

235Aspect ratio

A percentage, not a measurement: the sidewall is 35% as tall as the tire is wide, which is 120.8 mm or 4.75 inches.

3RConstruction

Radial construction.

418Wheel diameter

Mounts on a 18-inch wheel. Approved wheel widths run 11.5″ to 13.5″.

5109Load index

Each tire carries up to 2,271 lb (1,030 kg) at its maximum pressure.

6WSpeed rating

Rated for up to 168 mph sustained.

SpecificationInchesMetric
Overall diameter27.51699 mm
Section width13.58345 mm
Sidewall height4.75120.8 mm
Circumference86.42,195 mm
Revolutions per mile (calculated, unloaded)733.2456 per km
Revolutions per mile (published by manufacturers)755469 per km
Approved wheel width11.5–13.5292–343 mm

Speedometer error after switching to 345/35R18

Your actual speed– mph

Questions about 345/35R18

What is 345/35R18 in inches?

27.51 inches tall, 13.58 inches wide, on a 18-inch wheel. Written in inches, that is roughly 27.5×13.6R18.

How much does a 345/35R18 tire weigh?

Between 31.6 lb and 35.1 lb for the 2 tires listed here. The lightest is the Toyo Proxes R (SL); the heaviest is the Toyo Proxes RR (SL).

What wheel width do I need for 345/35R18?

Manufacturers approve 11.5–13.5″ wide wheels for this size.

How many revolutions per mile does a 345/35R18 make?

Published figures run 755 revolutions per mile. The calculated figure is 733.2, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 345/35R18 than 265/45R18?

0.12 inches taller on paper (27.51″ vs 27.39″), which raises the axle about 0.06″. Your speedometer will read about 0.4% slow.