Liner and shell modifications for ski boots. Title image.

Liner and shell modifications for ski boots

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We have described poorly fitting boots and lack of underfoot support, as the two main reasons causing boot fitting problems, in our previous articles on common boot fitting mistakes and custom footbeds. There are cases, however, when you can experience pain and discomfort even after a careful selection of boots and footbeds. The vast variety in anatomical shapes of human feet and ankles presents a problem for ski boot manufacturers. Namely, there is no ‘one-boot-fits-all’ solution. This is why boot fitters are manipulating factory boots in order to accommodate individual characteristics of different feet, including bony problems, such as exostosis (instep bumps, bunions, bone spurs, etc.), high or low volume feet, high or low arches, tight achilles tendons, large calf muscles, and more.

Ankle bone pain
There are two ways you can modify ski boots: shell modifications, liner modifications, or a combination of both.


When should you resort to shell or liner modifications?

In most cases, liner and shell modifications are the last resort of action for a boot fitter. After all, streching, cutting, and grinding boots, that cost as much as a new laptop, should be well thought out, the least. Here are the main reasons you should consider trusting your boot fitter whit such task:

Adding a U-shaped pad to the liner at the ankle bone can alleviate pain and keep the heel secured in its pocket
  • shell is too narrow, pressing against foot, causing pain
  • shell is too large, causing foot to slip and slide or heal to pop-out



Large boots are hard to work with. Boot shells simply can not be made smaller. This leaves boot fitters with the option to apply padding in certain areas, replace the liner with a thicker one, or insert heel or sole lifts to reduce space inside the shell. A replacement boot liner, can also be installed to fill the shell better.


Shell stretches and grinds, liner work

Narrow shells are easier to manipulate. Athletes are often looking for a performance fit and are opting for very narrow boots. These boots are then modified to accommodate the individual anatomy of the foot. Wherever pain or pressure is experienced by the athlete, the liner is modified (reduction of thickness, additional cushioning, etc.) or the shell is manipulated (stretching, grinding, heat moulding) by the boot fitter.

Shell stretch
Ankle bone stretch performed with the Sidas Croko clamp.

A shell stretch is performed by way of pre-heating the shell plastic (either with a heat gun, or infrared light). Then, mechanical force is applied to deform the shell in the desired new shape. Finally, the plastic is cooled to retain the new shape. One problem associated with shell stretches is related to the memory effect of many plastics. The stronger the memory effect, the more a plastic is returning to its original factory shape.

A shell grind is the action of driving an abrasive rotating head inside the shell to excavate plastic in order to accommodate a protruding bone for example. Shell grinds are preferred when the shell plastic is thick enough. Shell grinds are better on the overall appeal of the boot, since the result of the modification is not seen from the outside of the shell.


Common problems resolved with liner or shell modifications:

common pain points caused by ski boots

  • foot numbness
  • pain at ball of foot
  • pain at side of toes
  • top instep pain
  • arch cramps
  • ankle bone pain
  • bruised heel
  • shin pain



The problem triad

Remember that before you put your thrust in any boot fitter to slice and dice your precious ski boots, you should make sure the ski boot problem triad is resolved first:

  • boots are too big to hold the foot properly
  • foot is not supported by a proper footbed
  • limited dorsiflexion of foot is not remedied


How can Skisharki help you with your ski boot problems

Skisharki is offering complete range of boot fitting services, including selection of ski boots, moulding of custom footbeds, canting adjustments, liner and shell modifications, performed by certified boot fitters. We work with tools from established manufacturers, such as OrthoMove, Austria and Sidas, France.

Contact us for a free scheduled consultation.


Have more questions on boot fitting? Agree or disagree with our tips and advice? Leave us a comment bellow.

Skisharki is opening it’s first shop in Sofia in October. Read our location announcement post to find out where our shop will be housed.

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