Tuning and fitting
The goal of footbed tuning is to remove any remaining materials that are not needed. The human body is extremely sensitive to the surface on which it stands, and any pressure points affecting the foot. Thousandths of an inch of material will make a difference, and so that is the precision that I am working with.
I almost always start with the right foot. I don’t know why exactly. I was told that it represents some sort of ‘professional courtesy’. Reminds me of that joke about why sharks refuse to attack lawyers…
With the client standing on your surface plate, which should be level to at least a tenth of a degree, set their right foot on the corresponding footbed. Ascertain that their foot is reasonably matched to the contour, front to back and side to side. Be aware that excess material in the arch area, as well as the heel cup, can push the foot slightly off the contour. Make a pen mark on the big toe and another on the foot bed, to ensure accuracy in successive foot placements. Grind away any obvious material around the periphery of the footbed, but don’t get too aggressive. Grind away any obvious hotspots under the foot, and note any areas where the edges of the footbed are ‘biting’ the foot.
Ideally, providing accurate posting under the foot will account for structural mobility. When the foot is weighted, it should not collapse inward nor outward, nor should there be any significant discrepancies in support.
I will not describe exactly how I know when I have properly tuned a footbed, as that is something of a trade secret and must remain proprietary.
When you are sure that you have properly tuned the footbeds to both feet, test fit to the liners. Make certain that the liner is not affecting the alignment of the foot to footbed. If so, trim the footbed accordingly, to move it forward, backward, or side-to-side in the liner. Work in very small increments. When you are satisfied that the footbed fits both the foot and the liner, test fit in the shell.
It is not unusual for the confines of the boot shell to illuminate hot spots. The most common areas are directly under the first metatarsal head, under the arch, and in front of the heel on the medial side. The first metatarsal head has beneath it a sesamoid bone that is like a small kneecap. Some feet have two in this location. The function of this bone is to increase mechanical advantage at that joint. Usually, the sesamoid is protected and cushioned by a fatty pad, but this pad can be displaced, making the joint sensitive to pressure. If you grind away posting foam directly under this hot spot, you allow the blank to deflect slightly, removing pressure from that spot. Remove material very carefully, as it does not take much to make a difference, or to make the hot spot worse.
Under the arch, there is a large tendon (or ligament, I’m not sure anymore) that causes the big toe to plantar-flex. On some feet, this tendon/ligament is prominent, and relief must be provided for it by grinding a channel into the posting foam under the arch. Otherwise, the foot will cramp painfully. This is especially important for telemark and Nordic(xc) boots, where the dorsiflexion of the forefoot serves to exacerbate the prominence of this tendon/ligament.
With the foot properly supported, it will take on a slightly or dramatically different posture in the boot. This can make the boot feel tighter or looser, depending on the original conformation of the foot and also how much the boots have been used. A secure foot will also make the geometry of the boot more apparent, as far as forward lean, internal ramp, and medial lateral cuff alignment. These are all part of the alignment picture, but it is important that the footbeds are comfortable and functional before proceeding with further adjustments.
I like the client to ski on the footbeds for at least one day, as it often takes a few runs to fully settle into the boot. I caution the client that they should take their first run on something easy, so that they can determine which movements to discard from their skiing, and which movements to tone down.