Tire Sidewall Markings: M+S, Snowflake, Max Press and More

The sidewall is a label the law writes

The big numbers on a tire, like 225/45R17 94V, get most of the attention. Around them is a ring of smaller print, and most of it is there because a federal rule requires it.

FMVSS No. 139, the federal standard for passenger and light truck radial tires, splits the markings in two:

The rule also requires the maker's name or brand, and the tire identification number (TIN). For tires made from September 1, 2009, the full TIN goes on the intended outboard sidewall.

This guide covers the markings that other guides don't. For the main line, start with how to read tire size, or type a size into the decoder:

MAX PRESS and MAX LOAD

Near the bead you'll find something like MAX PRESS 51 PSI and MAX LOAD 1477 LBS.

• MAX PRESS is the maximum cold inflation pressure to which a tire may be inflated, in the federal standard's words. It's a ceiling, not a target. The pressure to run is on your door placard and in the owner's manual. Our blog post on why not to inflate to the max PSI explains why.
• MAX LOAD is the tire's maximum load rating, the most weight it's rated to carry. It corresponds to the load index in the size line. Our load index guide turns the number into pounds.

The federal rule also requires passenger tires at certain standard pressures to show the psi in parentheses after the kilopascal figure, and the pounds in parentheses after the kilograms, so both units appear.

The ply and cord line

Somewhere on the sidewall is a short line that lists what the tire is made of: how many plies sit under the tread and in the sidewall, and the cord material of each, such as polyester or steel. It's required by FMVSS 139, and it's the tire's construction in a single line. Our guide to the parts of a tire explains what each layer does.

TUBELESS and RADIAL

Both are required words. TUBELESS means the tire seals against the wheel and needs no inner tube. Michelin defines it simply: the tire does not require an inner tube. RADIAL confirms the construction the R in the size already tells you.

Load markings: XL, HL and Reinforced

Michelin lists XL / HL / Reinforced as tires designed to carry higher loads than standard tires of the same size. The federal standard defines an extra load tire as one designed to operate at higher loads and higher inflation pressure than the standard tire.

Michelin's advice for replacements: tires with reinforced or special load markings should always be replaced with an equivalent specification. If your placard calls for XL, the replacement needs to be XL too. Our guide to XL vs SL tires covers what that means for pressure.

On light truck tires, the load range letter (C, D, E and so on) does the same job. The federal rule requires it on each sidewall.

Size prefixes: P, LT, T and C

A letter can come before the size. Michelin lists them:

• P: passenger car
• LT: light truck
• T: temporary spare
• C: commercial van tire

Plenty of sizes have no prefix at all. The prefix matters when you replace a tire, because LT and passenger tires use different load tables and pressures.

M+S and the snowflake

Two winter-related marks look similar on a listing but mean different things. Michelin explains:

• M+S (mud and snow): designed for mud and snow conditions based on the manufacturer's criteria. No standardized snow test is behind it.
• 3PMSF, the three-peak mountain snowflake: the tire has met standardized testing requirements for verified winter performance.

In South Florida neither is likely to be the deciding factor, but they tell you how a tire was designed. The federal rule also sets out where the snowflake goes when a maker uses it.

Direction and side: arrows and OUTSIDE

Two markings tell the installer how to mount the tire:

• A rotation arrow marks a directional tire. Continental describes it as designed to roll forward in one direction only, with the arrow indicator printed on the sidewall. It must turn the way the arrow points.
• OUTSIDE (and sometimes INSIDE) marks an asymmetric tire, which Continental says has two separate tread designs, one on the inner half and another on the outer half. The OUTSIDE face goes out.

Both affect rotation. A directional tire stays on its side of the car unless it's remounted on the wheel. The rotation pattern tool shows which patterns your setup allows.

Run-flat marks

Run-flat tires carry their maker's own abbreviation, such as RFT, ZP, SSR or ROF, or simply "Run Flat". If a car came on run-flats and has no spare, the replacement plan matters. See our run-flat tires guide.

Checking a tire against your car

Read the size, load index, speed rating and any XL marking off your door placard, then compare with the sidewall. The Tire Size Finder helps read the placard, and the load and speed rating check compares two tires. When you're ready, shop by size. Tires ship free to the 48 contiguous states and DC, and Extreme Tires installs them at its Sunrise shop or by mobile van in Miami-Dade, Broward and Palm Beach.