M+S, or M&S: Mud and Snow; A tire that meets the Rubber Manufacturers Association (RMA) and Rubber Association of Canada (RAC) all-season tire definition.[20] These are all-weather tires, with self-cleaning tread and above-average traction in muddy or very light snowy conditions, and for low ambient temperatures. Spike tires have an additional letter, "E" (M+SE).