Ski boot modification posts

LINERS – HOW MUCH IS ENOUGH?

After you read my posts on foot and leg shape, ramp angle and what I look for in a ski boot you may have concluded that all you have to do is get the boot shell right, insert the liners and go skiing. Not quite. It is a little more complicated than that. In my experience, ski boot liners, especially custom-fit liners, can cause more problems than almost any other piece of ski equipment. “Seriously”, you say. “How is that possible? I thought boot liners were designed to help me ski better”. Maybe that was the intent. But I have yet to come across an explanation based on sound principles of science, let alone research that will withstand rigorous scrutiny, that supports the concept of attempting to immobilize the foot and leg within what amounts to an orthopaedic splint. If anyone knows of such an explanation and/or studies please let me know.

If you are like most skiers, you are probably reluctant to do anything significant to the liners of your boots, let alone do anything radical. It is reasonable to assume that if the manufacturer made the liner a certain it was probably for a good reason. There are several reasons I can think of that might explain why liners are made the way they are. But they have to do with manufacturing considerations, not skier performance.  The question is how much liner do I need to ski well? In Steve Podborski’s case, the question is how much liner did he need to ski not just well, but well enough to become the only non-European to win the World Cup Downhill title? The answer will probably surprise you. And let’s not forget that in the 1980-81 World Cup season where he almost won the downhill title he wasn’t even supposed to be skiing because he had torn his ACL 4 months before the start of the first race.

The photo below is of a stock soft-fabric Lange liner similar to the ones I built boots with in 1978-79.

Lange liner

The photo below is of the liner that Steve Podborski used in the ski boots that he wore when he almost won the World Cup Downhill title in 1980-81 and in the 1981-82 World Cup season when he won the the title. The liner is a little worse for wear because he skied in it from the start of the 1980-81 World Cup season until he retired.

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Two cap screws on the back of the moulded plastic spoiler of the liner secured it to the top of the boot shell cuff.

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The series of photos below are of the liner from the Head World Cup boot I am currently skiing in. The first photo is of the inner aspect of the right liner. The cutout below the cuff creates clearance for my inside ankle bone to move towards the shell wall as my foot pronates. The outer layer of the liner beside the ball of my foot has been cut away to allow the side of the ball of my foot to sit against the shell wall. The entire front portion of the liner has been removed to allow my foot to spread and elongate under load.

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This is the outer aspect of my right liner. The portion of the liner adjacent to my 5th metatarsal has been cut away to allow my foot to spread under load as it pronates.

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Top view of the right liner with no insole in place.

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Top view of the same liner with a Superfeet insole in place that I heated, put in a press and compressed it until it was dead flat.

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Bottom view of my liner. I intentionally purchased an insole that was too big then trimmed it to the exact length and shape of the base of my boot shell. Note how it slightly overhangs the front of the liner and especially how it overlaps the outer aspect of the sole of the liner.

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In my next post I will talk about how the tongue configuration I use makes a liner like this work.

PROBLEMATIC FEET AND LEGS

In my post, THE IDEAL SKIER’S FOOT AND LEG, I described the characteristics that I observed over the years that were consistently associated with the feet and legs of the best skiers and racers. When I first started to see this pattern I didn’t understand why these characteristics were associated with superior technical ability. What I did come to understand very quickly was that skiers with feet and leg shapes that were less than ideal had difficulty skiing without major modifications to their ski boots. The images below compare the ideal foot and leg shape to foot and leg shapes that are increasingly problematic. The dashed line indicates the top of the sides of the cuff of the ski boot shell. The vertical hash marks compare the width of the cross-sectional area of the ideal leg at the top of the sides of the cuff to foot and leg shapes that progressively less than ideal.

Foot and leg types

 

As the cross-sectional area of the legs becomes increasingly larger, it becomes increasingly difficult to accommodate the leg within the confines of a boot cuff. In some cases, leg shapes make it difficult to even close the cuff buckles without extending the bales or re-locating the buckles. These types of fleshy legs are mostly associated with females although some males have the extreme shape depicted in the righthand image.  Females with wide hips tend to have tibias that are either straight or angle inward as shown in the sketch below. This can be a big problem if the cant angle of a boot cuff cannot be adjusted sufficiently to obtain a neutral cuff alignment with legs. Boots with no cuff adjustment, like the old Lange XLR, had cuffs that were canted outward 3 degrees. This meant that female racers with tibias that were straight or angled inward would be hard on their inside edges in events like downhill if they tried to relax and let their skis glide.

Female with wide hipsSome females have tibias that angle inward and fleshy legs. Since the rear spoiler of the boot cuff determines the angle of (dorsi) flexion of the ankle joint, skiers with large calves and tibias that are straight or angle inward have too much forward lean and the wrong cuff cant. When I worked with female racers in the late ’70s and early ’80s it typically took a lot of ingenuity and a lot of work to come up with a solution.

The problem with ski boots is that the shape of the lower part of the shell and the shape of the cuff are usually designed to interface with each other in a specific configuration. This limits the ability to align the cuff in a different position with the lower shell. It was Alan Trimble, the boot tech for Lange USA, who taught me how to make cuts in the shell bottom where it interfaced with cuff, position the cuff in the desired orientation then rivet the two pieces together. Lange was one of the few boots that allowed for this kind of modification.

When I worked with Langes I had a supply of boot parts with no holes drilled in the cuffs. This made it easier to assemble boots in non-stock configurations. The soft Lange fabric liners with fit pockets made it easy to remove padding that was interfering with ankle-leg movements. A common complaint was pressure on the inside ankle bone and even along the inner aspect of the foot below and in front of the ankle. I got very good at stretching the shell wall in this area. I even had special tools made for this purpose. From feedback from racers, I came to know that it was important to not have any pressure on the inner aspect of the ankle and the area around it. But it took me years to understand why. Here is a short video clip that shows the movement of the ankle and leg that is fundamental to the technique racers such as Ligety and Shiffrin use. In a future post I will explain why and how this works.

 

 

THE IDEAL SKIER’S FOOT AND LEG

Do you have the ideal shape foot and leg for ski boots? Let’s find out.

Not long after I starting working on ski boots, I began to notice that the best skiers, those who made high performance skiing look easy, seemed to be able to ski in boots right out of the box that usually required major modifications for most skiers just to get their feet into. This small group of elite skiers consistently had very specific foot characteristics, especially the shape of their feet and legs. Although there were some exceptions, the feet of elite male skiers tended to be US size 8 or 9. Podborksi’s foot was a US men’s size 6. The feet of elite female skiers tended to be the equivalent of US men’s size 5 or 6 with some feet as small as size 4. As I worked on the boots of more National Ski Team racers I soon developed a reputation for being able to describe how a racer skied by studying their feet. On one occasion I was with a group of racers in the waiting area of a steak house. Unseen by me, Dave Murray came into the room. He snuck up on me while I was on my knees on the floor studying a racer’s foot. Dave put his bare foot in my face so to speak. Without looking up and without missing a beat I said, “What are you doing here Dave?”

The image below shows the characteristics I have identified as common to racers like Ligety, Shiffrin, Vonn and other World Cup racers. The characteristics of their feet and legs enables them to create the mechanics and biomechanics within the ski boot necessary for them to engage the external forces to drive their outside ski into a turn. Depending on a number of factors, including luck, racer’s with these foot characteristics can often ski in a boot right out of the box with minimal or no modifications. Modifications take their skiing to another whole level.  I believe that young racers such as Shiffrin make the connection with the right feel early in their career. Once a racer, or any sensitive skier, connects with the right feel, especially at an early age, they know as soon as they take a run in a new ski boot whether it will work for them. This group of skiers has the ‘magic touch’.

 

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Here’s what the right shape of leg looks like in the cuff of a ski boot. I align the cuff so the leg is centred in the cuff when the skier is standing on two feet in the boot shells with the feet hip width under the pelvis. Note the amount of space on either side of the shin. This is critical for reasons I will explain in a future post.

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In my next post I will show what problematic foot and leg shapes look like and the challenges presented in creating a functional environment in a ski boot.