Ski boot

Ski boots are specialized footwear that are used in skiing to provide a way to attach the skier to skis using ski bindings. This ski-boot-binding combination is used to effectively transmit control inputs from the skier to the snow.

Ski boots were originally made of leather and resembled standard winter boots. As skiing became more specialized as a form of recreation, so too did ski boots, leading to the splitting of designs between those for alpine skiing (downhill) and cross-country skiing. The later remain similar to standard footwear, but include an attachment point for the bindings. The former have become much more specialized, rising up the leg in order to transmit sideways rotations of the legs through the bindings and into the skis, a process known as "edging". A variety of techniques combine features of cross-country and downhill, notably Randoneé, and Telemark, and have led to further customization of boot styles to fill these niches.

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Alpine

Alpine ski boots have rigid soles and attach to the ski at both toe and heel using a spring-loaded binding. The interface between boot and binding is standardized by ISO 5355, which defines the size and shape of the hard plastic flanges on the toe and heel of the boot. Ski boots use the Mondo Point Sizing system, which is based on the metric system. There are four basic types of ski boot which vary in the way the ski boot closes around the lower leg: front-entry, rear-entry, mid-entry and open-throat ski boots.

Leather boots
Early ski boots were essentially winter boots with extensions on the front and rear of the heel to allow them to be clamped down with a cable binding. With the introduction of ski lifts, the need for cross-country skiing to get to the top of the hill was eliminated, and a much stiffer design was preferred. New boots that had been boiled in oil or soaked in glue were introduced to stiffen the upper cuff and allow more control over the sidewise motion of the ski. These were universally uncomfortable, especially during the break-in period when then were new, and also wore out very quickly as they softened up. Racers typically had only weeks to wear a particular pair before it was no longer useful.
Front-entry
"Front-entry" (or "top-entry", rarely "overlap") boots are the primary boot design for most of the history of downhill skiing. Developed by Bob Lange during the 1960s, these designs initially replaced the leather with new plastics to produce otherwise similar designs but with much longer lifetimes. However, these evolved rapidly so the flaps overlapped to provide a stiff cylindrical form when closed, dramatically improving control. The cuff around the leg also evolved over time, starting just over the ankle as in the leather designs, but rising to a point about half way to the knee by the 1970s. Only minor changes have occurred to this basic design since that period. Almost all modern front-entry boots consist of two sections, one around the foot and toe, and another around the lower leg. These are joined with a rivet that allows the left to pivot forward, but not to the sides, allowing tight control over the flex of the design. The overlapping flaps and four buckles that close them are almost universal on modern designs. When closed, the leg and cuff forms a single unit that is very stiff, allowing excellent control over the ski by transmitting even the smallest lateral movements of the leg to the ski. However, the rigid cuff that provides excellent control also makes them very difficult to put on and take off. They require the wearer to point their foot downward, slide it through the leg cuff, then rotate it forward into the toe area.
Side-entry
Introduced by Rosemont in the 1960s, side-entry boots consisted of an almost complete shell with a cut-out section on one side that hinged at the rear of the leg and swung to the side. Stepping in was very easy once the flap was opened, as the majority of the boot was open. After closing the flap, buckles locked the flap in place. The drawback to this design was that the fixed portion of the boot needed to support the majority of the loads, and had to be very strong, and early examples were made of fibreglass. Controlling forward flex in this design was difficult, as the two sides of the boot offered different amounts of mechanical support at the ankle. This design fell from use in the 1970s as front-entry boots became largely universal.
Rear-entry
Rear-entry boots were introduced in the 1980s to address the issue of getting conventional boots on and off, while also providing a generally better fit. In the rear-entry design, the entire foot area and sole are a single slipper-like unit, lacking the flaps on top of the forward foot area. The leg cuff is split in two, with front and rear sections that meet at the hinge point at the ankle. When a cable is released, the rear half of the cuff can pivot far to the rear, allowing the foot to be slid almost straight forward into the toe area. Closing the cable locks the moving rear portion forward onto the front half, forming the stiff cuff that pivots at the ankle like a conventional front-entry design. As the toe area is a single piece and lacks buckles for adjustment, rear-entry boots may have considerable "slop", and numerous systems of cables and plates were used on high-end models to address this problem. Rear-entry designs were very popular in the 1980s, notably Salomon designs like the SX91 Equipe, but they became increasingly unpopular in the 1990s due to their shunning by racers in search of a tighter fit. The join between the front and rear sections allowed the cuff to twist and reduced stiffness. Recent improvements to front-entry and mid-entry boots, primarily in the areas of comfort and ease of entry/exit, have diminished their popularity, though the mid-range models remain common as rental boots.
Mid-entry
These combine many of the strengths of both rear-entry and front-entry ski boots. Like the front-entry design, the mid-entry boot has a toe area with split flaps and conventional buckles. While still adjusting via buckles across the shin, the rear cuff of the boot is allowed to hinge back slightly to allow for a larger opening and thus an easier entry to the boot. In this way it provides the convenience of wearing of rear-entry ski boots, while at the same time offering much of the performance of front-entry ski boots. Introduced by Lange in the 1980s when rear-entry designs were popular, the mid-entry design has since become rare.
Open-throat
open-throat (or "three-piece") boots attempt to address the cuff firmness concerns of the rear- and mid-entry designs. Open-throat designs use a foot piece with no overlap on the top of the foot - there is a gap between the two halves. The foot plate rises above the ankle area, extending along the front of the leg. Like the rear-entry design, a separate section of the leg cuff can be rotated to the rear for entry. The key improvement is a third piece, an external tongue, that extends down the front of the left and over the toe. Buckles passing over the tongue clamp the entire assembly together, offering the stiffness of the front-entry design with the ease-of-entry of the rear-entry.
Shell modification
When the boot is physically stretched to allow for specific feet, typically by heating the plastic and pressing it into place. This is sometimes known as "blowing", as the shaping is sometimes accomplished by inflating balloon-like bags inside the shell.

Nordic

Cross Country
Cross country boots, like all Nordic equipment, attach to the ski usually only at the toe of the boot and are allowed to flex at the ball of the foot similarly to a normal shoe or boot. Cross Country boots generally use one of four attachment systems; NNN (New Nordic Norm), 75mm Nordic Norm ("three-pin" binding), d-ring, or SNS (Salomon Nordic System). A new Salomon Pilot binding is now widely used for racing because it uses two connection points so that the skier has more stability and control over the ski. As these boots are intended for travel over generally flat terrain, they are optimized for light weight and efficiency of motion.
Telemark
Telemark refers to a specific technique for making downhill turns on Nordic equipment. This has resulted in highly specialized equipment designed for better performance in a downhill setting. Until 1992 Telemark boots were basically heavy leather boots with the front of the sole adapted to the 75mm Nordic Norm. Since then plastic boots have become more and more common and now make up almost all Telemark boots. Plastic allows for a laterally stiffer boot while still allowing freedom of flex at the ball of the foot through the use of bellows. Boots intended for more cross country travel generally have a lower cuff, softer flex and lighter weight. Boots specialized for downhill use have higher cuffs, stiffer flex and heavier weight. Telemark boots are almost always equipped with a rubber sole.

Alpine Touring / Randonée

Alpine Touring boots are intended to allow both cross-country travel and downhill skiing using Alpine technique. Different models trade off light weight against downhill performance. They have a rockered, rubber sole to allow for easier walking. This means that they will not fit in ordinary alpine bindings. Instead, the interface between Alpine Touring boots and bindings is defined by ISO 9523. Other attachment methods exist and prominent amongst these are the Tech bindings and fittings that were first commercialized by Dynafit. As yet, these are not covered by an international standard.

See also

References

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