Mud and Snow Tire Marking: What M+S Really Means

M+S stands for mud and snow

The letters M+S, sometimes styled M&S, are molded into the sidewall of countless tires. They stand for Mud and Snow, and they tell you the manufacturer designed the tire with some consideration for loose surfaces and cold weather. That sounds useful, but the marking has a catch.

M+S is a self-declared marking. No federal standard defines what a tire must do to earn it, and no independent test verifies it. A tire maker can put M+S on a tire simply because the tread pattern has larger voids or extra sipes. As a result, the marking appears on all-season tires, all-terrain tires, mud-terrain tires, and even some summer-biased designs. It tells you more about the tire's category than its actual snow performance.

If you are comparing tires for winter use, treat M+S as a weak signal. It is better than nothing, but it does not compare to the 3PMSF symbol. For a deeper look at how tread patterns relate to weather, see our guide to tire tread versus weather.

M+S has no standardized performance test

The absence of a test requirement is the key difference between M+S and the 3PMSF symbol. Federal Motor Vehicle Safety Standard No. 139 (FMVSS 571.139) defines a snow tire as one that attains a traction index equal to or greater than 112 compared to the ASTM F2493 standard reference test tire, when tested on medium packed snow as described in ASTM F1805-20, and that is marked with the Alpine Symbol on at least one sidewall.

That definition is precise. It names the test surface, the reference tire, and a numeric threshold. A tire that does not reach a traction index of 112 cannot legally be called a snow tire under FMVSS 571.139, and it cannot wear the 3PMSF symbol. M+S has no equivalent requirement. Any tire can carry the letters M+S without ever touching a snow test course.

What does that mean for you? When you see M+S on a tire, you know the maker positioned it for mixed conditions, but you do not know how it performs on snow. When you see 3PMSF, you know the tire passed a defined test. For more on the symbol itself, read our article on the snow tire 3PMSF symbol.

The 3PMSF symbol has a real test behind it

The 3PMSF symbol, formally called the Alpine Symbol, is a pictogram of a mountain with a snowflake. Under FMVSS 571.139, it is reserved for tires that meet the snow traction index threshold of 112 or greater. The test uses the ASTM F2493 standard reference tire as a baseline, so the result is relative to a known reference, not an absolute number.

The test procedure, ASTM F1805-20, runs on medium packed snow. That is a specific condition, and it means the 3PMSF symbol certifies performance on packed snow, not on ice or deep powder. A tire with 3PMSF may still struggle on ice, and it may not have the tread depth for deep snow. The symbol is a meaningful piece of information, but it is not a guarantee of grip in every winter scenario.

FMVSS 571.139 applies to new pneumatic radial tires for vehicles with a gross vehicle weight rating of 10,000 pounds or less, excluding motorcycles and low speed vehicles. It does not apply to special trailer (ST) tires, farm implement (FI) tires, tires with rim diameters of 12 inches and below, T-type temporary spare tires, or light truck tires with a tread depth of 18/32 inch or greater. Those categories fall under other standards, which matters if you shop for a light truck tire with deep tread.

M+S versus 3PMSF at a glance

The table below summarizes the differences between the two markings. Use it as a quick reference when you read sidewalls.

The practical takeaway: 3PMSF is the only one of the two that carries a legal definition of snow performance under FMVSS 571.139. If you drive in snow, prioritize tires with the Alpine Symbol. If you only see M+S, you are looking at a general-purpose or all-terrain tire that may or may not handle snow well.

Related rules for light trucks and retreads

Light truck tires with a tread depth of 18/32 inch or greater are not covered by FMVSS 571.139. Instead, they fall under FMVSS 571.119, which applies to new pneumatic tires for vehicles with a GVWR above 10,000 pounds, and to light truck tires with deep tread for vehicles at or below that weight. Many mud-terrain tires for pickups and SUVs fit this category, and they often carry M+S markings as well. The 3PMSF symbol is less common on these deep-tread tires, so read the sidewall carefully before assuming a tire has been snow tested.

Retreaded passenger tires also get attention from the regulations. Under FMVSS 571.117, retreaded tires must meet several of the same requirements as new tires, including size, construction, bead unseating resistance, and strength. A retreader cannot mark a retreaded tire with a size designation, maximum load rating, or maximum inflation pressure greater than what the casing originally specified. When you buy a retreaded tire that claims M+S, the casing itself likely carried that marking from its original manufacture.

These rules matter because they change which markings you can trust on different tire classes. On a standard passenger tire, the 3PMSF symbol has real meaning. On a deep-tread light truck tire, you may need to rely on the brand's own specifications and tread design rather than a symbol. See our best light truck tires guide for models that balance off-road tread with on-road behavior.

What to pick for your driving

Your choice should start with your climate and road conditions, not with the letters on the sidewall. If you rarely see snow and want one set of tires year round, a good all-season tire with M+S is a reasonable fit. Look for a tire from a reputable brand and check its own snow performance claims, since M+S itself does not certify anything.

If you face snow and ice regularly, buy a tire with the 3PMSF symbol. Dedicated winter tires use compounds and tread patterns designed for cold weather, and the 3PMSF marking confirms they passed the packed snow test. All-weather tires are a middle ground: they carry 3PMSF in many cases, and they stay mounted year round, which suits drivers who want winter capability without a seasonal swap.

For off-road driving in mud and loose soil, M+S appears on most mud-terrain tires, but that is not the marking you should shop by. Look for a mud-terrain tread pattern with the right load rating for your truck. M+S on a mud-terrain tire tells you little beyond the tire's intended category. See our mud terrain tires guide for options that suit serious off-road use.

Always check the full sidewall for other markings before you decide. The load index, speed rating, and DOT date code all matter. Read our tire sidewall markings article to learn what every symbol means, and our tire load index rating guide to avoid overloading your vehicle.

If you drive a passenger car or SUV and want one set of tires that handles snow without a winter changeover, the all weather tires guide is a strong starting point. For dedicated snow season grip, the winter tires guide covers the current field.

What to pick for your use

Questions

What does M+S stand for?

M+S stands for Mud and Snow. It is a self-declared marking that indicates a tire is designed for some mud and light snow conditions, but it carries no standardized performance requirement.

Is an M+S tire a winter tire?

Not necessarily. M+S has no test requirement behind it, so a tire with M+S may not perform well on packed snow. A winter tire under FMVSS 571.139 must reach a traction index of at least 112 and display the 3PMSF Alpine Symbol.

Do all winter tires carry the 3PMSF symbol?

Tires that meet the FMVSS 571.139 definition of a snow tire must be marked with the Alpine Symbol on at least one sidewall. If you buy a tire marketed for winter use, check for the 3PMSF mark to confirm it passed the packed snow test.

Can I use M+S tires year round?

Yes, in most cases. M+S appears on many all-season and all-terrain tires that are designed for year round use. The marking itself does not limit the tire to winter, but you should check the speed rating and tread design for your needs.

What is the Alpine Symbol?

The Alpine Symbol, widely known as 3PMSF, is the three peaked mountain with a snowflake pictogram. Federal Motor Vehicle Safety Standard No. 139 requires it on tires that achieve a traction index of 112 or greater on packed snow per ASTM F1805-20.

Does M+S guarantee mud performance?

No. M+S is not backed by a mud performance test. A mud terrain tire with aggressive tread blocks is designed for mud, but the M+S marking alone does not verify it. Look at the tread pattern and the tire's intended use.