Two winter markings show up on truck tire sidewalls, and they are not the same thing. One describes a tread shape. The other is a test result.
M+S is a shape, not a score
M+S (mud and snow) describes tread geometry — groove width, void area, block edges. The manufacturer self-certifies it against a dimensional definition; no tire is driven on snow to earn it. Most highway drive tires carry M+S, which is why the marking on its own tells you very little about how a tire behaves on a packed grade.
The snowflake is earned on snow
The Three-Peak Mountain Snowflake (3PMSF) is awarded only after a tire clears a standardized snow-traction test against a reference tire on packed snow. It is a measured threshold, not a marketing badge. A tire carrying the snowflake also carries M+S; the reverse is not true.
Two severe-snow rated products sit in our drive tires: the Firestone FD692 and the Yokohama 715R. Both are drive-position tires, and that is not an accident.
Why a fleet specs a severe-snow drive
Traction lives on the drive axle. Steer and trailer positions are built for even wear, rolling resistance and casing life — put aggressive snow tread there and you pay for it every mile of the year. Spec'ing severe-snow on the drives is the targeted move: more bite pulling a grade, more margin on the mornings before the plows catch up, and no penalty on positions where it would not have helped anyway. Mixed fleets commonly run severe-snow drives only on the trucks assigned to northern or mountain lanes.
What chain laws do and do not accept
This is the part that costs people money. US chain laws are written around chains. When a state puts a pass under chain control, a snowflake-rated drive tire does not exempt a commercial vehicle — the snow-tire allowances in the lower control levels are written for light vehicles, not trucks. Several western states also require commercial vehicles to carry chains through the winter months whether or not conditions call for hanging them.
The snowflake buys you traction in the conditions before chain control. It does not buy you a pass through the control point.
Reading it on a product page
Our spec tables show axle position, ply and load range, service description, max load single and dual, max pressure and tread depth. There is no season row on a truck tire page. Severe-snow rating is called out on the product itself, and if you are not sure which drive tire fits your lanes, tell us where you run and we will quote accordingly.