Snow chains
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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. Snow chains are usually attached to the drive wheels of a vehicle (e.g. the front wheels on a front-wheel drive car), though all four wheels should be chained to provide extra stability. Some owner's manuals for four-wheel drive cars specify that two specific wheels can be chained, leaving the other two unchained if necessary.
Snow chains are sold as paired sets of two. You should buy chains that match your tire size (tire width and radius numbers can be found printed on the tire).
A set of chains are placed on the wheels that are connected to the drive train in order to gain traction in icey, snowy or muddy conditions.
Front Wheel Drive Vehicles: Most passenger cars are front wheel powered vehicles, so the snow chains would be placed on the two front tires. (Though all four wheels should be chained to provide extra stability as long as the vehicle's owner's manual does not indicate chains cannot be used on all four wheels.)
Rear Wheel Drive Vehicles: Pickup trucks, older cars, sporty cars and most German cars are usually rear wheeled drive so the chains are placed on the rear tires. (Though all four wheels should be chained to provide extra stability as long as the vehicle's owner's manual does not indicate chains cannot be used on all four wheels.)
Four Wheel Drive Vehicles: Four wheel vehicles can use two pairs of chains to cover all four wheels. With only one pair of chains they are often put on the rear wheels, but can be placed on the front wheels instead for the added steering and braking benefit. (All four wheels should be chained to provide extra stability as long as the vehicle's owner's manual does not indicate chains cannot be used on all four wheels.)
In snowy conditions, transportation authorities often require snow chains to be fitted on vehicles that lack four-wheel drive and proper tires. These requirements are usually enforced by checkpoints, before which eligible drivers must have snow-chains fitted on their cars. Near such checkpoints, chains can often be fitted professionally for a fee. Snow chains limit the speed of the automobile to approximately 30 mph (50 km/h), and reduce fuel efficiency.
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[edit] Tire Chain Sizing
U.S. tires have standardized sizing information. This information can be found on the sidewalls of the tires. The first letter(s) is for the vehicle type, P for passenger, LT for light truck. The next 3 digit number gives the tire's width in millimeters. The next 2 digit number gives the tire's height to width ratio. The next letter is R, which stands for radial ply tires (not radius) followed by the last 2 digit number, which is the rim diameter for the vehicle's wheels.
Additionally, the correct SAE class of snow chains must be installed, based on the wheel clearance of the vehicle.
| SAE Traction Device Class | Minimum Tread-Face Clearance (A) | Minimum Side-Wall Clearance (B) |
|---|---|---|
| Class S | 1.46” | .59” |
| Class U | 1.97” | .91” |
| Class W | 2.50” | 1.50” |
The SAE Class "S" well clearance is most popular in today's smaller, front wheel vehicles.
The classes are defined as follows:
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.
Please refer to your vehicle owner's manual for correct SAE class.
[edit] Common chain failures
- Driving too fast with chains. Maximum speed 20 to 30 mph (per the chain's owner's manual)
- Driving on dry roads with chains for extended periods of time.
- Not securing the chains tightly enough. You should tighten the chains a second time after driving for a little bit. Chains that come loose should be refastened or removed before they wrap around your vehicle's drive axle (which can cause expensive damage).
- Tensioners or adjusters may be required. (Some tire chains do not require tensioners and may be damaged if tensioners are used, see your chain's owner's manual.)
[edit] Other names for traction devices placed on wheels of cars and trucks
- Diamond Chains
- Link Chains - Same as Tire Chains or Snow Chains
- Traction Cables - 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 Spikes" occasionally seen on Saturns or other vehicles, a device roughly similar to the shape of a spider which is mounted onto the tires from the side, easier to mount than traditional chains, but there has been a little controversy over potential failure of these.
[edit] Other uses
- Snow chains are sometimes used as a percussion insturment the song Nowhere To Run is a well-known example of where this was used.
