Snow chains

This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (February 2009)

Snow chains on a front-wheel drive automobile.

Snow chains, or tire chains, are devices which are affixed to the tires of vehicles to provide superior traction when driving through snow and ice^{[citation needed]}.

Snow chains are attached to the drive wheels of a vehicle. Chains are usually sold in pairs and must be purchased to match a particular tire size (tire diameter and tread width). Driving with chains will reduce fuel efficiency and can limit the speed of the automobile to approximately 50 km/h (30 mph).

Deployment

In snowy conditions, transportation authorities may require snow chains to be fitted on vehicles. This can apply to all vehicles, or those that lack certain motive combinations such as four-wheel drive and/or specific classifications of tires. Local requirements may be enforced at checkpoints. Snow chains should always be fitted to one or more drive axles of a vehicle, with varying requirements 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' being required to have snow chains fitted when conditions and/or signage require it.

United States

Tires come with standardized tire code sizing information, found on the sidewalls of the tires. The first letter, or letters, give the vehicle type (P for passenger, LT for light truck). The next three digits gives the tire's width in millimeters. The middle two digit number gives the tire's height-to-width ratio. The next character is a letter 'R' which stands for radial ply tires (rather than radius). followed by a final two digit number giving the rim diameter for the vehicle's wheels.

Additionally, the correct Society of Automotive Engineers (SAE) class of snow chains must be installed, based on the wheel clearance of the vehicle.

The SAE Class "S" well clearance is a common requirement on newer cars, especially if aftermarket wider, low-profile, or larger tires and/or wheels are fitted.

The classes are defined as follows:^{[citation needed]}

• SAE Class S - Regular (non-reinforced) passenger tire traction devices for vehicles with restricted wheel well clearance.
• SAE Class U - Regular (non-reinforced) and lug-reinforced passenger tire traction devices for vehicles with regular (non-restricted) wheel well clearances.
• SAE Class W - Passenger tire traction devices that use light truck components, as well as some light truck traction devices.

Common chain failures

• Driving too fast with chains. Maximum speed recommended in the chain's owner's manual - generally 30 to 50 km/h (20-30 mph).
• Driving on dry roads with chains for extended periods of time.
• Not securing the chains tightly enough. Chains should be tightened a second time after driving a short distance. Chains that come loose should be refastened or removed before they wrap around the vehicle's drive axle.
• Tensioners or adjusters may be required. (Some tire chains do not require tensioners and may be damaged if tensioners are used)

Alternatives

• Diamond chains - diamond pattern car or truck chains
• Link chains - same as tire chains or snow chains
• Traction cables - formed from cable wire instead of chain links
• Cable chains - Same as traction cables
• Snow cables - Same as traction cables
• Snow tires, tires with deep grooves to grab snow to aid traction.
• Studded tires - snow tires with metal studs used in icy conditions.
• Spider shaped chain mounted onto the tires from the side.
• Sock - fabric rather than chain or cable.
• Polyurethane or rubber instead of chain.

Legality of use

Laws vary considerably concerning the legality of the use of snow chains. Some jurisdictions may require their use in certain weather conditions or during certain months of the year, whilst other states or jurisdictions may ban their use altogether to preserve the surface of the roads.^{[citation needed]}

See also

• Automatic snow chains

External links

• Tire Rack article: Tire Chains for Winter Use
• Comparision of United States' snow chain legal status per state, published by the Wisconsin Motor Carriers Association

• Yosemite National Park Tire Chains Page
• Snow chains for trucks, cars and tractors in Russia