Short answer
Look for the three-peak mountain snowflake symbol. Under the U.S. Tire Manufacturers Association definition, it marks tires that meet a severe-snow traction test, not just the M+S marking.
Match the size and load rating to your vehicle's placard, especially on trucks, and book before the first snow.
The symbol that matters
USTMA's definition requires a tested snow grip index of at least 1.10 (14-inch reference tire) or 1.12 (16-inch reference) using ASTM F1805 on medium-packed snow, plus the M+S marking and the mountain/snowflake pictograph.
Size and load
Use the tire sizes on the door-jamb placard. Trucks that tow or plow need the right load range. Ask us to look it up by VIN.
Winter vs. all-season vs. all-weather
| All-season (M+S only) | Winter / all-weather with 3PMSF | |
|---|---|---|
| Severe-snow tested | No | Yes, meets USTMA severe-snow threshold |
| Marking | M+S | M+S plus three-peak mountain snowflake |
| Year-round use | Yes | Winter tires: seasonal. All-weather 3PMSF: year-round |
When to book
Book before the first real snow. Plan where your off-season set will live.
Before you start
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A local next step
Swant Graber Motors (Chevrolet, Ram, Dodge) is at 1690 E Division Ave, 715-537-5657. Swant Graber Ford is across Highway 8 at 1697 E Division Ave, 715-537-9500. Barron, WI 54812. Send your question or the vehicle details before you visit and the right person will be ready. Shop new and used inventory.
Questions
What does the mountain snowflake on a tire mean?
It marks a tire that meets the USTMA severe-snow traction definition, tested on medium-packed snow against a reference tire. M+S alone does not require that test.
