Snow chains, or
tire chains, are devices fitted to the
tires
of
vehicles
to provide increased
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 other areas prohibit the use of chains, as they can deteriorate road surfaces.
Legality of use
Laws vary considerably regarding the legality of snow chain use. Some countries require them in certain snowy conditions or during certain months of the year, while other countries prohibit their use altogether to preserve road surfaces.