In skiing, a ski binding is an attachment which anchors the ski boot to the ski. There are different types of bindings for different types of skiing:
Bindings by type of skiing
The vast majority of bindings for Alpine skiing work by fixing the ski boot to the ski at the toe and heel. The binding attaches the boot to the ski, but to reduce injury also allows the boot to release in case of a fall. The boot is released by the binding if a certain amount of torque is applied (usually created by the weight of a falling skier). The amount of torque required to release the boot is adjusted by turning a screw on the toe and heel piece. This is called the DIN setting. The correct DIN setting is based on height, weight, ski boot sole length, the skiing style of the skier (cautious, average, or aggressive) and, age (if the skier is 50 years old or older). The DIN is usually set by a technician when skis are rented or bought. Adjusting a binding without the proper test equipment can cause problems with release and may be dangerous to the skier.
Bindings can be sold alone to be mounted to "flat" skis or can be integrated systems. While integrated systems generally provide a more natural flex, better power transmission, and a larger sweet spot, they also add more distance between the boot and the ski. While this is helpful in achieving higher edge angles, the high lift can strain the knees when skiing powder, and will make landings less stable. For this reason, most powder or freestyle skis are sold flat, while most carving and race skis come with an integrated binding system.
Alpine ski bindings employ the use of a snow brake to prevent the ski from moving whilst not attached to a boot. Snow brakes work by the use of a sprung square 'C' shape, typically made of metal, which makes contact with the snow. When a ski boot is put in the ski binding, the brake pivots under the downward pressure and runs parallel with the ski allowing free movement. When the boot comes out of the ski, the brakes spring out perpendicular to the ski and stop the ski from sliding.
There are three common Nordic binding systems:
- The NNN (New Nordic Norm), where a bar in the toe of the shoe is hooked into a catch in the binding. Also exists in the more rugged BC (Back Country) variant. Two small ridges run along the binding, corresponding with slits in the boot. It should be noted that there have been several versions of NNN as Rottefella have evolved the binding, and the first NNN version is not compatible with later (current) designs.
- SNS (Salomon Nordic System; marketed by Salomon) looks very similar to NNN binding, except it has one large ridge and the bar is narrower. Three variants exist: Profil, the standard model; Pilot, specific for either skate-style or classic-style cross-country skiing, and the "X-Adventure" variant for backcountry skiing. While Pilot skate boots can be used with a normal Profil binding, Profil boots cannot be used with Pilot skate setups. Because of its ease of use it is quite common, though in some places NNN equipment (broadly comparable in terms of cost and performance) is easier to come by and hence used more. Previous SNS systems exist with a loop protruding from the front of the boot rather than a bar flush with the front, and these are obsolete and no longer available.
- 75 mm (Rottefella, Nordic Norm, 3-pin) This is the original, classic system found on cross country skis, invented by Bror With. These bindings, once the standard, are no longer as popular as they were but still hold a significant share of the market for mid-weight touring setups with relatively heavy boots, as typically used for hut-to-hut touring in Norway. In this system the binding has three small pins that stick up. The toe of the boot and has three holes that line up with the pins. The boot is then clamped down by a bail. Despite the decreasing use of the 3 pin "rat trap" binding in lighter cross country, the characteristic "duckbill" toe it uses is still assumed in the design of heavier cable bindings, and 75 mm boots are still widely available, especially for telemark technique and more rugged touring. A similar system with a 50 mm "duckbill" once existed for lighter setups, but is obsolete and no longer available.
Like Nordic bindings, Telemark bindings fix only the toe leaving the heel free to move. The main difference is that Telemark bindings are more heavy-duty to withstand the increased forces encountered in high speed descents. The cable binding (aka Kandahar binding), where the toe section of the boot is anchored, and an adjustable cable around the heel (for which there is a groove in the heel of the shoe) secures the boot. Used for cross-country (to a certain extent), Telemark and ski jumping.
While binding designs vary, before 2007 almost all dedicated Telemark models had been designed to fit boots with 75mm Nordic Norm "duckbill" toes. However, in late 2007 Rottefella introduced the New Telemark Norm (NTN) binding which uses a different boot sole, co-developed with the Crispi and Scarpa boot companies.
Alpine ski touring
Also known as Randonee, an Alpine Touring ski is a special ski binding that allows the heel to be clipped down to the ski when skiing downhill, but which allows it to be released when climbing.
Skiboard and Snowblade Non-release binding
and Salomon's Snowblade have used non-release plate bindings. The reason being that skiboards and snowblades have traditionally been 100 cm in length or less, so the torque during a fall was assumed to be small enough that a releasable binding was not necessary. However, in recent years, as skiboarding has become a more established niche sport, releasable bindings have become a viable option to decrease the chances of injury. Spruce Ski
created a riser which adapts between the standard 4 cm by 4 cm four-hole skiboard binding and standard ski bindings; furthermore, Spruce began selling their 120cm skiboard in the 2005-06 season which are only available with their releasable setup. Additionally, Salomon now offers most of their Snowblades with releasable ski bindings as well. Many riders still prefer the plate-style bindings, and SnowJam and Bomber both make high quality plate bindings.
Modern ski bindings are based on the Fennoscandian model of the 19th century. The bindings of Telemark ski
skis were developed from the Ugro-Lapp type. See History of skiing