Anatomy of a Ski Boot

Whether you're in the market for new ski boots, or just want to get learned, we help you know your boot from liner to last.
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Whether you're in the market for new ski boots, or just want to get learned, we help you know your boot from liner to last.

Common Terms Defined:

anatomy: boots

>> Last: The shape of the interior cavity of a boot. For a given size, some boots are designed to be wide and roomy, some sculpted to be snug and tight. “Last” is the cobbler’s term for the wooden, foot-shaped blank around which shoes of a particular size were built.

>> Lugs (toe and heel): Lugs are the portions of the shell's sole that interface with a ski binding. They must meet industry standards for quality and dimensions. On some boots they’re replaceable in the event of wear.

>> Liner: The liner is the removable inner boot, usually made of foams, leather, textiles and injected plastic components. It provides padding for the foot to protect it from the rigid plastic of the shell. Race boots have minimal padding, using firm materials such as cork, in order to give the athlete instantaneous “on/off” connection to the boot shell and thus the ski. At the other end of the spectrum, comfort/“sport” level boots have deeply cushioned liners; they feel great, but offer almost no communication between foot and shell.

>> Footbed: The footbed is the removable platform inside the liner. It’s the platform on which the foot rests, and as such is the all important interface between the sole of a skier’s foot and his or her ski. Stock footbeds vary widely in quality, but are generally flimsy, poorly articulated to fit individual feet, and lacking in support, especially of the arch and heel.  Custom footbeds, molded to the foot of the skier by a bootfitter, are a great first step in boot customization. The personalized interface between skier and boot improves the quickness and sensitivity of the boot. Cost: typically about $150

What You Should Know:

Boots basically come in three varieties, defined mostly by their widths. The three categories are race, all-mountain high-performance, and sport/recreation. Last widths range from about 95 mm in the tightest race boots to 105 mm in the sloppiest sport/rec boots. Race boots are not only the narrowest, but have the thinnest, firmest liners (often using only cork for padding), since racers are willing to sacrifice comfort for ultimate performance. All-mountain boots are medium-snug, with moderately padded liners, in order to combine all-day comfort with sufficient performance. Sport/recreation boots are excessively wide and are designed to feel good, even at the expense of performance. Be aware that what feels good in the shop might turn out to be too loose on the hill. In a too-loose boot, the skier doesn’t have the fit-tension necessary to control a ski. Furthermore, a sloppy fit allows the foot to slide around inside the boot, often leading to greater discomfort in the long run. Remember also that thickly padded liners will pack out extensively, with a resulting loss of both performance and comfort. A general rule: snug is good. If you have problems with tight spots, a bootfitter can always help. If a boot’s too big, there’s relatively little he or she can do to help.

Flex ratings, or indexes, indicate how stiff a boot is. There is no quantitatively standardized scale for indexing flex. Manufacturers have informally developed one, but the ratings of one company can differ from those of another. Flex ratings may at one time have been tied to measurements of plastic hardness (durometer), but there’s much more than that to the stiffness of a boot: wall thicknesses, hinge points, spine rivets, height of cuff attachment, etc. European engineers are said to be at work on a standardized rating system. Meanwhile, the flex ratings that exist today do give a skier an idea of how soft or stiff a boot’s flex is, especially in relation to other models in a line. Most rating scales go from about 60 for a junior boot to 150 for a World Cup race boot.

Boots can be tilted—or “canted”—inward or outward in relation to the ski to accommodate the biomechanics of the skier. Cant is often confused with shaft-alignment, which merely refers to the inward or outward angling of the cuff. Boots are usually canted by grinding the sole at an angle or by inserting wedges (if the toe and heel plates are removable) to give a skier better access to all four ski edges.

Boot Constructions:

Three-piece overlap: The traditional boot design has a lower shell and an upper cuff, attached and hinged on either side of the ankle, with plastic wings that overlap each other over the foot and in front of the shin, drawn together by a traditional buckling system.

Cabrio/mid-entry/shell-tongue: In a cabrio design, the shell has a tongue, which opens forward like a convertible (hence “cabrio”). It’s easy to get into and out of, and proponents love the quality of the flex that the shell-tongue provides. Originally popularized as the Flexon Comp—which is still fondly cherished by many—this design has more recently been revived by two brands, Dalbello, with its Krypton line, and Full Tilt, which has revived the Flexon design, using the same molds and closure systems.

Alpine/AT Hybrids: The hottest new category in boots blends the tourability of an alpine touring (AT) boot with the power and quickness of a traditional alpine boot. It’s favored by experts who demand better downhill performance than traditional AT boots provide and are willing to put up with increased weight during moderate hikes or climbing-skin ascents, often aided by resort lifts. They typical incorporate rubber along the soles, for better traction on rocks and ice (or icy parking lots), and a ski-walk device on the spine that lets the boot cuff release to upright and beyond, for improved hiking functionality (or improved après comfort while standing at the bar).

Want more definitions?

>> Shell: The plastic exterior components of the boot, usually comprising two components: the cuff and the lower.

>> Cuff: The cuff is the removable upper portion of the shell, attached at hinge points on either side of the ankle.

>> Shaft/cuff alignment: Shaft or cuff alignment, not to be confused with true canting, refers to the inward or outward tilt of the cuff in relation to the lower shell. It’s usually adjustable on at least one side of the cuff—typically by merely loosening a screw—so that the cuff can be angled to match the angle of the skier's lower leg in relation to his or her foot.

>> Bootboard: The bootboard is the removable floor of the boot shell—the platform on which the liner rests. It’s also sometimes referred to by its Italian name, "zeppa." Bootboards exist for two reasons: because it’s difficult to inject plastic of sufficient thickness without warping, and because the bootboard allows for customization and improves insulation.

>> Buckles: You don’t think about buckles until you have a problem with one. But a lot of thought goes into them. There are basically three components to most buckles: the catch (or ladder), the bail, and the lever. Buckles are an expensive component, so you’ll see cheaper buckles on less expensive boots. Ideally, all buckles are metal (usually aluminum). At lower prices, manufacturers replace metal with plastic, all or in part, with a resulting decline in durability. On high-performance models, manufacturers also take great pains to make the buckles sleek and thin, so they won’t cause “boot-out,” which occurs when a steeply angulated boot makes contact with the snow, causing the ski edge to lose contact with the snow.


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