Originally Posted by elduderino
I understand that placing a socked foot in the unlined shell, the expectation is 5-15mm space behind the heel.
What I don't really understand is how that measurement trumps everything else as an initial indicator. It would also appear to me that when the liner is correctly placed in the boot, it would be against the back/heel portion and the excess would then be in the toe box area.
It is true that if you pull the foot to the rear of any shell the excess will end up at the toes---the problem is, in a larger shell the foot will not end up in the center of the boot---the boot is centered over the ski but the foot is loading the heel of the boot shell more(it's in the back end of the boot). this will cause problems with fore/aft balance and back seat sking---not to mention that most often people don't tighten the ankle enough to hold the heel back, oddly they tighten up on the foot with the 2 lower buckles, the result is cold, numb feet. This will still allow the foot and liner to move fore/aft in the shell, changing the balance point over and over again. In a 5 to 15mm shell fit the foot center will end up pretty close to the shell center and if the ankle is pulled back by the second strap from the top you won't bump your toes.
We have noted that folks with large calves will buy boots 2 sizes larger which will allow them to seem to stand up at the knee---in this scenario the heel will be pushed forward by calf loading at the top of the shell and lint will gather behind the heel in the foot bed. There toes will be pushed forward into the narrow portion of the shell and they often get the shell widened to accommodate this issue,
not a good solution, now there foot is forward of the boot sole center and their hips are hanging out behind there heels. They will bend over at the waist to try to get forward and burn up there quads and core muscles.
Getting started with the right length shell will support better skiing comfort, balance and control, it is a starting point which can not be ignored if you are looking for CONTROL with comfort. A big shell fit ends up with neither.