Any modern, well-tuned, shaped ski will carve a beautiful arc if tipped on edge and pressured just right.

Ski boots are how skis are tipped and pressured. They are the direct link between thought and execution.

It’s ironic, then, that the most crucial piece of ski equipment – one that can be used for years – is often a hurried, uninformed, almost afterthought purchase.

Jeff Bergeron, owner of Boot Fixation in Breckenridge (and Denver) and one of the few premier boot-fitters in the country, sees the results: tingling toes, aching arches, blisters and painful pressure points, sore knees, burning thighs and aching backs.

Beyond the pain, ill-fitting boots cause problems with technique. They are a barrier to harnessing the inherent turning power of shaped skis, Bergeron said. Skiers might skid, not carve their turns. They may be able to turn left but not right, or vice versa. Skiers might be pitched forward or pushed into the back seat. To compensate, skiers with ill-fitting boots twist and rotate their upper bodies.

They push and twist their poor knees in an attempt to make their skis react. They never have a sure sense of their balance point. They feel bad. They ski badly.

“Eighty percent of bad technique is the body’s attempt to make up for poor power transmission,” Bergeron said.

“The boot is your lever to your ski, transmitting foot and leg motion.

“It is the critical link, and it is where the biggest gains (in performance) can be made.”

Bergeron’s advice: Do your homework or seek the advice of an experienced boot-fitter to find the boot that best matches the shape of your foot and your physiology.

This is particularly critical for women, because they need a shell that accommodates their hips and stance (usually knock-kneed).

Choose the right size

Boots should fit more snugly than most skiers imagine. A good boot-fitter can relieve hot spots and pressure points in a tight-fitting boot, but it’s difficult to make a sloppy boot fit well.

Once those basics are taken care of, an experienced boot-fitter then has a variety of ways to tweak a boot to compensate for bowed or knock-kneed legs, feet that roll in or out, or body posture that interferes with finding balance on a ski.

A correctly fit boot will allow a skier to transmit power directly from his or her big muscles – the abdomen and thighs – directly through the knee and ankle, down to the midfoot and on to the ski.

Bergeron said a boot adjusted to the peculiarities of a skier’s body is much like the taut suspension of a Porsche.

When the wheel is turned, the motion is transmitted directly to the wheels.

A poor-fitting boot, he said, is like the mushy, wallowing suspension of a 1970s Cadillac.

“You want as direct, easy and powerful a connection as possible,” Bergeron said.

“Everybody has an athletic position that works best. The idea of high-performance boot-fitting is to find that position.

“When boots are set up properly, a skier should be able to change edges easily and evenly as well as feel relaxed yet powerful in every ski turn.”

Stance and knee tracking

A correctly fit boot will center the mass of the knee directly over the midpoint of the boot’s toe, allowing a skier to transmit power from his or her body core to the ski’s edge. A knock-kneed or bowlegged stance dissipates that power, preventing a skier from turning his or her skis in a consistent, dynamic way.

Custom foot beds

Custom foot beds are the foundation of a skier’s stance, said Bergeron. Foot beds correct feet that roll in or out and put the ankle in the proper position. Bergeron makes foot beds that adjust the position of the forefoot, arch and heel. Foot beds can be transferred to new boots, sometimes with minor modifications, and can last up to 10 years.

Canting

Canting is often used to align body parts – feet, ankles, calves and knees – so they work together to apply pressure to a ski quickly and easily. Canting can mean planing the sole of a boot, modifying the internal parts of the boot, or adding shims under the liner, either at the heel, arch or forefoot. The cuff of the boot also can be adjusted.

118-point check

Bergeron said he can make up to 118 checks and changes to a boot. He said most skiers have three to eight significant issues that when corrected make boots more comfortable and skiing more relaxing.

Body alignment

The holy grail of boot-fitting is to align the body so a skier can transmit power from the big muscles in his or her abdomen and thighs down through the knee, directly to the ankle and foot. That creates a long, strong outside leg, a hallmark of modern ski technique.

Achieving balance

A correctly fit boot will allow a skier at rest to stand in balance without using muscular effort and allow him or her to make subtle, quick changes in body position while skiing. Boots properly aligned with a skier’s body will allow equal edging of both skis, another characteristic of a modern ski turn.

Boot-fitting aids

A balanced fore-aft stance on skis can be achieved with rubber spacers screwed into the sole of a boot, either at the heel or toe. The “ramp angle” of a boot can also be changed by grinding the boot board, the plastic insert in the interior of the boot shell beneath the inner boot. Spacers can even be installed under the toe or heel of a binding to correct stance issues.