Snow chains

Snow chains, or tire chains, are devices fitted to the tires of vehicles to provide maximum traction when driving through snow and ice.

Snow chains attach to the drive wheels of a vehicle or special systems deploy chains which swing under the tires automatically. Although named after steel chain, snow chains may be made of other materials and in a variety of patterns and strengths. Chains are usually sold in pairs and often must be purchased to match a particular tire size (tire diameter and tread width), although some designs can be adjusted to fit various sizes of tire. Driving with chains reduces fuel efficiency, and can reduce the allowable speed of the automobile to approximately 50 km/h (30 mph), but increase traction and braking on snowy or icy surfaces. Some regions require chains to be used under some weather conditions but some areas prohibit the use of chains which can deteriorate road surfaces.

Snow chains were invented in 1904 by Harry D. Weed in Canastota, New York. Weed received U.S. Patent Number 768495 for his "Grip-Tread for Pneumatic Tires" on August 23, 1904. Weed's great-grandson, James Weed, said that Harry got the idea of creating chains for tires when he saw drivers wrap rope, or even vines, around their tires to increase traction on muddy or snowy roads, which were very common at the turn of the 20th century (although at this time, most people in rural Northern regions wouldn't bother driving automobiles in the winter at all, since roads were usually rolled for use with horse-drawn sleighs, rather than plowed, so automobiles were generally not winter vehicles, for a variety of reasons; this was true until the 1930s or 40s in some areas. Only in urban areas was it feasible to remove snow from streets.). He sought to make a traction device that was more durable and would work with snow as well as mud.

In July 1935, the Canadian Auguste Trudeau obtained a patent for his tread and anti-skidding chain.

In snowy conditions, transportation authorities may require that snow chains or other traction aids be installed on vehicles, or at least supplied for them. This can apply to all vehicles, or only those without other traction aids, such as four-wheel drive or special tires. Local requirements may be enforced at checkpoints or by other type of inspection. Snow chains should be installed on one or more drive axles of the vehicle, with requirements varying for dual-tire or multi-driven-axle vehicles that range from 'one pair of tires on a driven axle' to 'all tires on all driven axles', possibly also one or both steering (front) wheels, requiring snow chains whenever required by signage or conditions.

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