Ski Boot - Alpine

Alpine

Modern 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 Mondopoint system, which is based on the metric system. There are several basic types of ski boot in use which vary in the way the boot closes around the lower leg: front-entry, rear-entry and open-throat ski boots. Several other designs have fallen from favour over time, or have been niche players throughout: side-entry, mid-entry and external frame designs.

Common designs

Front-entry

Front-entry (or "top-entry", rarely "overlap") boots have been the primary boot design for most of the history of downhill skiing. The design evolved from existing leather boot though several steps.

In 1956, the Swiss factory Henke introduced the buckle boot, using over-center levered latches patented by Hans Martin to replace laces. Laces spread the load across a number of eyelets in the leather, whereas the buckles concentrated the load at only a few points. To spread it back out again, the boots featured C-shaped flaps that stretched over the opening where the laces would be, to the side where the buckles were located. These had the added advantage of also helping block snow from entering the front of the boot.

Beginning around 1960 Bob Lange experimented with ways to replace leather with plastic. Early examples used a lace-up design, but in 1964 he combined a new, more flexible polyurethane plastic with the overlapping flap and buckle system from Henke to produce the first recognizably modern ski boot. Production examples appeared in 1966, and when Nancy Greene started winning races on them, the plastic boot became a must-have item. Replacing leather with plastic dramatically improved stiffness and control, along with durability and warmth (leather boots had a way of soaking through, which led to wet, frozen feet). Over time the cuff around the leg evolved upward, starting just over the ankle like leather boots, but rising to a point about half way to the knee by the 1980s. Only minor changes have occurred to this basic design since then.

Almost all modern front-entry boots consist of two sections, one around the foot, and another around the lower leg. These are joined by rivets/rotating joints near the ankle that allows the leg to pivot forward, but not to the sides. This allows excellent control by transmitting even the smallest lateral movements of the leg to the ski. However, the rigid cuff also makes them very difficult to put on and take off. Additionally, because the boot clamps across the foot, pulling the sides inward, it is difficult to produce a single design that fits a range of foot shapes and sizes. This leads to shell modification services, when the boot is stretched to fit the skier's foot, typically by heating the plastic and pressing it into place. This is also known as "blowing" ("punching", "pushing"). Sometimes material will be ground off the boot to provide more room. This is normally used only with front-entry designs, other designs normally include much more room in the foot area as they do not clamp down the same way.

Rear-entry

Rear-entry boots were brought to market in the early 1970s by the Hanson brothers to address the issue of getting conventional boots on and off, while also providing a generally better fit. Rear-entry designs were very popular in the 1980s, notably Salomon designs like the racing-oriented SX 91 Equipe.

In the rear-entry design, the entire foot area and sole are a single unit similar to a slipper. The leg cuff is split in two, with front and rear sections that meet at the hinge point at the ankle. The rear half of the cuff can pivot far to the rear, opening wide for easy entry. Closing a cable locks the moving rear portion forward onto the front half, forming the stiff cuff that pivots around rivets 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 various systems of cables, plates or foam-filled bladders were used to address this. The upside of this approach is that the foot area can be made larger, fitting almost any foot.

The rear entry design fell from popularity in the 1990s due to their shunning by racers in search of a closer fit. Recent improvements to front-entry and mid-entry boots, primarily in the areas of comfort and ease of entry/exit, have diminished the popularity of rear-entry designs even in recreational roles, though mid-range models remain common as rental boots.

Three-piece

Three-piece (or "open-throat") boots were first developed by Mel Dalebout (around 1969), who introduced a rigid magnesium boot shell in that year (Brixia did the same thing with their aluminum shell at around the same time). The big advantage was that the main shell was a single piece that was convex at all points, meaning it could be easily produced using a plug mould. Conventional boots with overlapping flaps required more complex moulding processes. Engineers at Henke, Heierling, Sanmarco and Caber saw the advantage for high-speed moulding, and plastic three-piece boots were on the market by 1972, when Roland Collombin won the Olympic downhill in the Henke Strato.

Boot designer Sven Coomer later improved the design with a corrugated tongue, and this technique was commercialized by Comfort Products, an Aspen, Colo. company owned by the ex-ski racer Erik Giese. Giese licensed Coomer's concept to the Swiss company Raichle-Molitor; the company introduced it in 1979 as the Flexon, which became very popular among downhill racers and mogul skiers. The Flexon was extremely popular among professional skiers, especially for moguls and freestyle, but a series of business blunders put Raichle out of business in the late 1990s. Several companies produce three-piece designs today, and they are once again becoming popular models.

The design closely resembles a conventional front-entry design, with separate foot and leg sections riveted at the ankle. However, the overlapping flaps of these designs are cut away, leaving a slot-like opening running down the front of the leg and over the foot. A separate plastic tongue is positioned over this opening on the front of the boot, and buckled down to close it. The open cuff (the "throat") makes the boots easy to get on and off, and the shaping of the tongue allows complete control over the forward flex. A single shell can be used with different tongues to provide any needed flex pattern from racing-stiff to freestyle-soft.

Other designs

Hybrid leather

The introduction of plastic boots in the 1960s led a number of companies to introduce "hybrid" boots with plastic inserts for additional lateral strength. These were widespread in the late 1960s, especially from the large collection of Italian bookmakers in Montebelluna, before they started introducing all-plastic designs of their own. Typical designs used a plastic insert wrapping around the heel area and extending up to just below the ankle, allowing the skier to force their foot sideways and offering some edging control. Others, notably 1968's Raichle Fibre Jet, wrapped a soft leather boot in an external fibreglass shell, producing a side-entry design that was not particularly successful. Hybrid designs often incorporated elements of the side-entry or three-piece designs. The Fibre Jet shared much in common with the Rosemount design, for instance.

Side-entry

Introduced by Rosemount in 1965, side-entry design consisted of an almost completely enclosed shell with a cut-out section on one side. The cut-out was covered by a flap that hinged along the back of the boot, swinging to the rear to open. Stepping in was very easy, simply sliding the foot sideways in through the opening, then swinging the flap closed and stretching a fabric cover over it to seal it. As the upper and lower sections both opened, metal plates were needed on the sides to connect the two mechanically. A problem was that the boot did not meet perfectly along the join, allowing snow to force its way into the boot, although improvements were continuous. This design fell from use in the 1970s as higher-cuff front-entry boots became largely universal.

Mid-entry

These designs combine elements of both rear-entry and front-entry ski boots. Like the front-entry design, the mid-entry boot has a toe area with flaps over the top closed with conventional buckles. The foot part of the boot rises higher than conventional designs, mounting a rivet system similar to the one at the ankle. Two plates, front and back, are mounted to this rivet, allowing them to open wide for easy entry. Once they are buckled shut, they form a leg cuff like that of a conventional front-entry design. Introduced by Lange in the 1980s when rear-entry designs were popular, the mid-entry design has since become rare. They are mostly widely seen in rental shops and intended for beginner skiers.

External frames

The ski boot provides three functions; protecting the foot from the elements, providing a mounting point for the binding, and transmitting forces between the leg and the ski. In theory, there's no reason these have to be combined in a single unit, and several designs have split these functions up. One example is the Nava System from the 1980s, which used a soft boot that clipped into custom bindings, and an arm that extended up from the rear binding to wrap around the leg and provide lateral control. Several newer designs have been attempted over time, notably the Apex Ski Boot that uses a relatively small carbon fibre framework that clips into conventional bindings and provides lateral control, and a semi-soft boot for comfort and protection. The Apex design is similar to some inline skates that feature step-out shoes, and has a strong resemblance to snowboard binding systems.

Knee-highs

In 1980 four designs were introduced that all rose to a point just under the knee. They were normal ski boots below, but used an extended tongue that fastened around the upper leg using a variety of methods. They offered much greater edging control, and were quickly copied by many other companies. They all disappeared by 1983, a victim largely of fashion - ski pants wouldn't fit over them. None are produced today.