We’ve Gone Insane — Ski Boot Casting

Post by WildSnow.com blogger | November 24, 2008      

People sometimes say I’m nuts. This might be proof. Tired of guessing about how much “volume” ski boots have, or how suitable the fit is for a given type of foot? WildSnow intends to answer those questions once and for all. I spent some time last week figuring out a way of “casting” the interior of a ski boot, so I can basically make a copy of the boot last. The process uses all hardware store and grocery store materials (injection foam insulation), and results in an accurate mold. I’ll be charting this stuff over the next few weeks, and I’ll start a page just for the data. Any suggestions on what measurements you guys would like to have at your fingertips? I’m thinking things like width at ball of foot, height of built-in arch, height at instep and so forth.

Backcountry skiing boots

Dynafit ZZero at the casting call, some Scarpa casts to right.

We’ve got access to many brands and boot models. Challenge is normalizing size so comparison is meaningful. Since my size tends to be a 28 we’re sticking with that for most, but we’ll drop one shell size down on occasion. In our charts, we’ll make clear what sole length and mondo size the boot is.

You can also measure boot interiors using a molded thermoform liner, but doing so means making sure the liner fills all the voids and so forth. Plus our WildSnow method results in a cast we can store and refer back to when necessary.


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40 Responses to “We’ve Gone Insane — Ski Boot Casting”

  1. Sierra Journal November 24th, 2008 11:27 am

    Awesome! Can’t wait to see the results. Still trying to figure out which brand fits my ridiculously wide, high-volume hobbit feet.

  2. Dostie November 24th, 2008 11:29 am

    Awesome Lou! Been thinking about this for years. Psyched you’re taking the first step.

  3. Terry November 24th, 2008 11:44 am

    Additionally, seems like water displacement volumes at various benchmarks (top of ankle, front of foot, top height, etc) might be useful along with circumferences. Interesting (and tedious) project. Happy Thanksgiving….snow is on the way!

  4. Tom G November 24th, 2008 12:15 pm

    This is really cool, good job Lou! I think the critical measurments would be interior length, width at ball of foot, height at instep, circuference around heel/ankle (think of how the middle scarpa buckle wraps) and circumference around the lower leg just above the ankle. You’ll probably want to standardize how you buckle the boots as that obviously makes a difference. Maybe make the cast with all of the buckles at their mid-point. Also, it would be really useful to see the measurements for some common alpine boots like a Lange race boot and a maybe a Tecnica Icon. For each boot please report the cuff height measured inside the boot (front, back, both sides). A lot of people find AT boots to be too low in cuff height realtive to alpine boots, so it would be good to better understand the differences. Think about posting instructions for your casting method so that people to cast their own boots – you could build quite a data set with reader supplied data.

  5. Sam Reese November 24th, 2008 12:54 pm

    Finally, we can all know just how much beer it will take to fill a ski boot shell!

  6. tony November 24th, 2008 1:28 pm

    Great idea, lou! How do you get the casts out of the shell without deforming them?

  7. Lou November 24th, 2008 1:34 pm

    If I decide to measure volume with liquid displacement, I’ll use Tecate.

    Tony, the foam is quite resilient and they pull out easily. I spray pure silicone spray inside the boot before starting, as a release agent, and the foam is inside a plastic bag. The stuff is space age sticky and even sticks to Pebax!

  8. Nick November 24th, 2008 1:42 pm

    I would be interested in seeing photos or tracings of the toe area from above – to confirm my suspicion that Scarpas have a much more symmetrical toe box than other boots. That is what they look like from outside and what my long straight big toe feels.

  9. Troll2739 November 24th, 2008 1:50 pm

    Anthropologists have used rape seed (and others) for at least one hundred years to measure cranial capacity. To avoid leakage, the cranial sutures are usually filled with soft wax like beeswax. Might work here.

  10. Julie November 24th, 2008 2:21 pm

    This is an incredible idea! I’ve owned several pairs of skis over the years and rented on occasion, and this information would certainly make finding the perfect boots a lot easier. Some sort of diagram or photo showing exactly where you’re taking the measurements (so one can measure his or her feet/ankles/legs at the same place) might be useful.

    I’m wondering what you’re going to do with all of these casts when you’ve gotten all your measurements. I’m envisioning an art exhibit…

  11. Lou November 24th, 2008 2:21 pm

    I’ve got a nice caliper set coming, and I’ll measure the cuff by simply taking a few interior measurements, no need for the casting in that case. Where the casting is essential is for the ankle area and foot, as it’s really tough to get good measurements for that area without cutting the boot in half.

    Everyone, remember that immense differences in fit can be made by how much volume the liner takes up. To that end, I might even mold the inside of some lasted liners if I have time. Would be cool to compare that to a mold of the shell the liner came out of.

    Some of the boot makers will also supply interior measurements, but I wonder at how accurate those are as who knows what generation of last design they’re taken from. Besides, to be consistent I should do all the measurements with the same method, that way if the foam expands a tiny bit after the cast is removed, or something like that, all the measurements will still work for comparison between boots.

  12. Hamish November 24th, 2008 1:52 pm

    I sometimes find that a boot that fits my calf is voluminous around my foot so perhaps a measurement of just the lower mold? Just to determine relative volume in the below-the-ankle section?

  13. Lou November 24th, 2008 3:25 pm

    Anyone from the 60s remember the infamous plaster casters? This is the boot maker’s version of that. Google it, and no overt discussion here please, but you’ll get a laugh out of it.

  14. North.Bend November 24th, 2008 3:54 pm

    Lou, great idea. Question: Will you be providing the thickness of each respective liner as well? The shell fit, while important, doesn”t always tell the whole story…a fat liner can hide alot of volume, as you know.

    Width across forefoot, depth of boot at high arch, lenth from heel to toe, total height from bootboard to top of cuff and width at heel are all numbers that I feel would be relevant. As well as the liner thickness in all of those various spots.

    Good luck with your project, look forward to the results.

  15. Lou November 24th, 2008 4:31 pm

    North.Bend, I’ll try to do something with liners, but my opinion is that liners are easy to fit and mod, what’s 100 times as important is the difference in the shells. Also, tons of people use custom thermo liners, so knowing different shell sizes is key for them, as the liner is a constant. My calipers can do some liner measuring, so perhaps I’ll chart some of that as well.

  16. Marc November 24th, 2008 5:30 pm

    Here’s another vote for measuring the width at the ankle. maybe I’m partial because of my skinny little ankles and this is a big deal for me.

    And it better start really snowing soon before you go completely nuts. Proof of total insanity would be if you started slicing the casts every cm or so (in all 3 planes) and posted the profiles.

  17. Lou November 24th, 2008 5:36 pm

    LOL, maniacally.

  18. Casagrande November 24th, 2008 8:45 pm

    Uh, certifiable comes to mind. What does your wife think of this project?!

  19. John Gloor November 24th, 2008 9:04 pm

    Lou, now that you will have all the boot measurements, is there anyway to see how much liner is required on average to avoid pressure points like the sixth toe area or the big toe bunion? Maybe ask for foot widths from readers here and correlate them to boot reviews and happy/unhappy feet.

  20. stephen November 24th, 2008 9:53 pm

    I’d also like to see ankle width, plus a tracing of the forefoot to get an idea of how pointed the toe box is. The more information the better though. Great idea!

  21. sock_monkey November 24th, 2008 11:30 pm

    Fantastic, Lou.

    Here’s my wish list for measurements:

    -width and length at ankle and top of cuff (or horizontal cross section)
    -cuff height.
    -width at ball, instep, heel
    -height at ball, instep

    —-less important —-

    -arch height, length, centre location (relative to heel or toe)
    -distance between max width (ball of foot) and front/back of boot (or simply an horizontal outline of this section to give an idea of shape)
    -vertical cross section of the boot at instep/arch centre, ball of foot

    —- really cool —-

    -provide pictures of the molds front, sides and top so we can try to build a 3d model from the pictures

  22. Lou November 25th, 2008 7:24 am

    Thanks for the great ideas everyone! I’ll hit everything I can!

  23. Dave Cramer November 25th, 2008 9:52 am

    i have an unusual approach to this subject. I go to a shop, and actually put the boot on my foot. I find I can learn a lot about how the boot fits using this method.

  24. RobinB November 25th, 2008 1:13 pm

    Producing 3D digital files from these is not that far of a stretch…

  25. Lou November 25th, 2008 3:36 pm

    Dave, why didn’t _I_ think of that!

  26. Lou November 25th, 2008 3:37 pm

    And too bad all shops don’t have all boots, and are not located in all places (grin). That’s where WildSnow comes in?

  27. simon November 26th, 2008 1:12 pm

    sounds like a great idea,

    perhaps some stripes draw around the casts, or better still a use a projector to illuminate the casts with a striped pattern, a few photos and a 3d profile should be quite reasonable to create.

    remeber to comment if the shells have been modified prior to making the casts.

    Good luck!!

    look foward to the results

  28. Michael November 27th, 2008 8:13 am

    Thank you! Thank you! Thank you!
    I’ve been looking for this info for years.
    I have very low volume/narrow feet and have never been able to try all the different AT boots to find the best fit.

    Have a great Thanksgiving.


  29. Evan November 27th, 2008 1:16 pm

    I think it may be interesting to compare foward lean angles with those listed by the mfg. May be fun to know how that angle is measured and how it translates to reality and skeletons and skiing techniques.

  30. Lou November 27th, 2008 3:02 pm

    Evan, the problem with that is knowing exactly how the mfg. measures the angle… I’ll do my best.

  31. Funhog November 29th, 2008 9:28 am

    Funny, I was just looking at new AT boots yesterday, and today I go to your site, and voila, you are doing a volume test!! I am a person who needs your findings more than most, as I have bunions (ouch). People with normal feet should rejoice, cause these bunions seriously mess with your footwear choices. I was unable to ski for more than one hour or so, before the foot pain drove me off the hill. I did not find relief until I found a shop with the skill to punch out my Technica HVs (high volume) bunion area almost 1 inch! People on the lift would look at my boots and think I was from the planet Mars! Anyway, it looks like a great project, and I will be monitoring your progress. Please contact me or leave a blog, an I will be glad to offer any bunion related help that I can.

  32. joey west December 1st, 2008 7:03 am

    I hope you have a pair of Crispi Diablos you can cast!

    I am sure you have thought of this but…buckle settings have an impact on volume and fit.. how are you going to standardize how tight the buckles are across different brands and models when you make the molds? Molding at the tightest buckle setting would give minimum volume… Molding without anything buckled would give an idea of the boots ‘natural’ or open volume… …

    Thanks for taking on this project! it will be helpful.

  33. Lou December 1st, 2008 7:47 am

    Joey, what we can’t standardize we can’t, but we’ll provide a height at midfoot as well as a volume rating (low, medium, high). I’m still having trouble with wrinkles in the plastic bags I use to line the boots, as well as getting the foam to fill the toe area with resistance from the plastic bag. I’m getting enough measurements to start a chart, but have to refine the process.

    What’s been interesting is how similar the shell lasts are between brands.

    In terms of liners, they’re so flexible they’d be tough to mold with my system. But they’re so easily customized I’ve never felt liner fit was a big deal. What’s critical is how the shell relates to your foot, the liner can be molded etc. to just about any foot shape. More, many people use after market liners or 100% heat molded liners, and in those cases giving liner dimensions would be moot.

  34. Zelda December 26th, 2008 3:01 pm

    Thank you so much! I have a wide foot and my current ski boots cause me a great deal of pain. I’ve been trying to find more information on the width of ski boots or see if they come in different widths, but it’s almost impossible to find this information. It’s like the ski industry has never even considered this issue. I’m looking forward to reading your findings!

  35. Rene Paup January 13th, 2009 5:49 pm

    Glad someone is doing something about this. My needs are width across the forefoot,i.e. across the big ball, the height of the arch, (I have high arches) and the width of the heel, (I have narrow heels). Lang changed their last and they no longer can be fit to my foot.

  36. Mark Rogers November 14th, 2010 10:28 pm

    Bump…How’s this project coming along? I have feet like Rene Paup’s so I have a lot of trouble finding boots that fit too.

  37. Lou November 15th, 2010 7:57 am

    Mark, apologies, but that project has been going slower than I like. I seem to have overextended myself over the past year, and had to put some things off. I do enjoy doing it, however, so I’ll pick it up as soon as possible. One thing to note is that my impression was that most boots are quite similar, and that much of what people experience in fit variations is caused by the liner, thickness of footbed, etc. Lesson is to, yes, find the best shell. But work that liner and footbed!

  38. Dan November 17th, 2010 6:31 pm

    Hi Lou and company, This is an outstanding effort! Been using your site for all sorts of invaluable info, including this. I’ve been holding out on AT boots for awhile now. I’ve had a discount pair of Alpine boots that work fine in my Duke bindings on my 09/10 BD Zealots. The extra weight and hiking discomfort hasn’t yet been enough for me to spend $700 on boots I haven’t been wowed by yet, or am not sure of what will happen when they break in, and not sure how they’ll perform on the hill. I’ve read the stereotypes of all the brands, tried on models available from many of the brands. REI folks werent’ much help on characterizing my foot. I think I have a foot that runs narrow, low volume, and has a moderate arch. Whether that’s correct or not remains to be verified. I do know in my track and field days (10 years ago), several miles on Nike running shoes always resulted in burning arches, but Adidas felt amazing when I switched over. Anyways, comparing stereotypes, I figured Garmonts would fit best, and Scarpa the worst. I tried both (Adrenaline, Megaride, Spirit 3, 4, plus Dynafit Zzero 4 U TF, Black Diamond Factor and Megaride). Surprisingly, I thought the Scarpas felt better out of the box (tied with Dynafits), the BD’s both seemed to feel the best, with the Garmonts taking last. Being confused, plus overwhelmed with advertised performance levels (flex index) of all, I gave up, and resorted back to hiking in my Alpine boots for last year. It’s been mostly extended side country, but now I’m looking into Avy classes, and giving up lifts altogether. Boot deals on last years models sparked interest on them agian, but now the boot companies are all coming out with lighter but stiffer versions (ultimate boots). With what you’ve seen so far does that mean brands like Scarpa are changing their lasts to smaller volume? Rather than trying to guess, I really just need to find a high quality boot fitter who can steer me in the right direction for starting off. I’d love to drive the 5 hours out to Aspen to visit the fitters you speak of out there, but can you recommend any high quality boot fitters in around Denver, or along front range?

    After I get the fit/brand figured out, I’ll need to choose the proper flex for my Duke/Zealot setup. I’ve always thought stiffer = better (therefore Factor, Titan, and Mobe/Hurricane), but some speak of progressive flex, and using softer boots to lever the skis in steep chutes, deep snow, etc. Can you explain this?

    Also, as a side note, can you recommend first rate sources for Avy I within CO and/or WY? What credentials should they have?

    Thanks for your time!

  39. Lou November 18th, 2010 7:25 am

    Dan, all the AT boots are more similar than they are different.

    The manufacturers blow in the wind of what they think the latest trends are. For a few years there, they went all-out competing to see who could make the alpine boot that toured. That was good, as certain folks need that (those who ski hard, or just are not good enough skiers to use a softer boot and still enjoy it).

    Now the pendulum of marketing and design has swung to the lightweight side. The easiest way to make a lighter boot is to, yes, make it lower volume and eliminate things like buckles and cuff canting rivets. So you’ll see more of that. But to the boot maker’s credit they are innovating like crazy to see who can come up with light boots that still ski and have the features we need.

    I think Black Diamond really stirred things up when they created a whole boot line practically out of thin air, and had them made in the far east, as compared to companies that have been trudging along with incremental innovation for decades and sometimes seemed to be stuck in the same design paradigm. That has definitely changed! So good on ALL the boot makers now for getting on the case (though the plastic ski boot is still basically the same thing it was more than 40 years ago, and that’s getting a bit tiresome.)

    At any rate, now is the best time in history for AT boot shoppers to find the exact boot for their needs, so don’t despair!

    Instead, yes, go to a boot fitter and get clear on all your doubts. Try Larry:

  40. Val September 27th, 2012 1:07 pm

    Dear Lou,

    I know you posted the idea of boot casting some years ago but I found your post only now. What a great idea!
    I essentially would like to replicate what you did for ski boot for another type of boots and I was wondering if you could send me the details of your casting process:
    1) Which type of injection foam you used?
    2) How did you injected it?
    3) Does the silicone spray you applied before ruin the inside of the boot?
    4) How long do you have to wait before the foam get stiff?

    Thank you!

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