Bootfitting for Backcountry Ski Touring

Post by blogger | December 26, 2005      

Spent more quality time backcountry skiing and lift skiing with my latest test boots. The stock liner is a robust inner boot that works for most people, but in my case, no joy. I’ve got narrow feet, and want room for my toes in a backcountry skiing and ski alpinism boot, so I went with a shell size larger than I’d have picked for alpine skiing. Even after careful molding of the G-Fit, with no sock and a thick custom footbed, I ended up with a hair too much room. Solution: grab a pair of thermal molded liners I had kicking around from another boot, and bingo, perfect fit.

Baking backcountry skiing boot liners
My Thermoflex liners being baked at Sportfeet in Aspen.

As it nearly always does, a boot fitting problem yields to innovation and experimentation. Here are a few tips I’ve learned from this and dozens of other such incidents:

Pick the correct shell size for backcountry skiing by placing bare foot in shell, touching end with toes, then seeing how many stacked fingers you can fit behind your heel. Any more than a 2 finger stack and the backcountry skiing boot shell is too big. Less than one-and-one-half fingers and it’s probably too small. In some cases (as in mine) you’ll be between shell sizes. If that happens try fitting the smaller shell first, but remember it’ll probably be colder and you may have problems with getting enough length for your toes. The larger shell will be warmer and easier to get comfortable for touring, but you may have problems getting the fit tight enough for downhill skiing.

Be willing to experiment. Try different liners and play around with custom footbeds. Different brands have VERY different fits, so don’t get stuck on one brand/model.

When molding thermo liners for backcountry skiing (or alpine skiing) use a nylon stocking instead of a sock. When doing so, mold with the usual toe cap (under the stocking), but add a small wad of duct tap to any toe areas that tend to need more room (cover with tape so the spacer doesn’t stick to the inside of the toe cap). Liners molded this way may feel slightly tight for a few days, but after a few days use they’ll usually pack out to perfection. If not, re-mold with a thin sock.

You can mold thermo liners at home, but doing so can be a real freak show the first time you try it. Best is to do it at a shop with expert help, then mold at home after you’ve seen how the pros do it.

Here are thermo boot liner baking instructions gleaned from my own experience and various sources on web:

Put the liners in a convection oven at 210 – 250º F (depending on brand) for 12-13 minutes, or use regular oven with plank of wood on aluminum foil to keep radiant heat from scorching the liners. If you use a regular oven, pre-heat then turn off soon after placing the liner in the oven, to prevent scorching. With nearly all ovens, use an accurate oven thermometer to check temperature.

Most liners use similar temperatures, yet care is required. Sometimes you can find the correct temperature in the pamphlet sold with the boot. Other times, the information will be arcane and difficult to acquire. Examples:

Scarpa’s heat blower system is set at 246°F, this is an Intuition liner so their excellent home molding process applies. If using an oven I’d tend to go a little cooler, try 240°F.

Atomic Memory Fit oven operates at 117°C – 242.6°F. This would probably work for using an oven at home, provided your thermometer was accurate.

When the liners are “baked” in an oven they will look big and puffy. It’s better to heat them in the boot as you won’t have to struggle with placing the wormy puffed liner into the boot before you put your foot in.

If you have any sensitive areas on your foot that could result in rubbing/pressure problems, duct tape foam spacers on such areas to create extra room in the liner. Ditto for ends of toes that may not have enough room. If you use thick spacers, bevel the edges.

Put your footbeds on the bottom of your feet, and a toe cap over your toes. If you don’t have a toe cap, use tips from 2-pair of socks. Place a women’s stocking foot over everything to hold the parts together. Don’t wear any sort of sock, as the liners will pack out and compress quite a bit as you use them, and fitting them without a sock will make them tight enought fit perfectly with a sock after just a few days of use.

The toe cap should cover your toes and come down to the ball of your foot.

Prepare backcountry skiing boot shells by making sure buckles are easily worked and power strap is out of the way. Switch boots to walk mode. Sprinkle some talc powder in shells to ease entry of puffy baked liner — or better, heat liner while it’s in the shell (see Intuition method linked above). Make sure there is nothing inside the boot that will catch the liner and tear it, or keep it from going in smoothly. If such things exist, cover with some duct tape or something so the liner can go in easily. Many ski touring boots have a vertical tongue of plastic in inside the shell in the rear, take care this doesn’t get folded down while you’re molding.

Following must be done quickly:

(Assuming you’re using the oven method), take the liner out of the oven and wrap it around your foot, making sure the overlap or tongue is configured correctly. Have an assistant shift the liner around so that the seam on the bottom of the liner sole goes exactly down the center of your foot. Having help from an assistant is important.

Stand in the liner and pull up on the cuff to make sure your foot is all the way in. Then put your foot (with the liner) into the shell. This method prevents wrinkles from forming in the liner due to compression, and it also prevents the footbed from getting warped. When placing foot in shell, have your assistant hold the shell open and help the liner slide in.

To further make sure that your foot is all the way in the liner, have your assistant hold down the shell of the liner, and lift your heel and the liner up about 2 inches. Then while pulling up on the liner, push the liner back down into the shell with your foot. Do this procedure twice, but don’t over-stretch the liner by pulling it up too much towards your knee. Too much stretching and pulling will result in the liner being too thin and high. The foam inside the liner, when heated, is easily damaged.

Tighten the boot buckles half-tight, so that the liner just molds to your foot. Do not tighten the buckles any further while the liner cools.

Hit your heel on the floor several times, and flex a few times, to get your foot into the heel pocket of the boot. Do the process with the other foot. Then wait 10 minutes while standing with your toes up on a book or some kind of spacer that’s an inch or two high, so your heels are low. Try to maintain a static stance that’s similar to your downhill skiing stance. If you require cuff alignment (canting) be aware of which way to bias the mold. For example, if you are knock kneed use a slightly bowlegged stance while you wait for the liner to cool. Stay in the boots until the liner cools completely.

To fine tune, you can reheat parts of the liner with a heat gun to puff it out a bit, or compress on a boot press if it’s too tight in spot areas. Most liners also “ski in” a bit, so slight imperfections in the molding process can be remedied by just going out and using.

You can re-bake liners a number of times, but each time they will puff slightly less.


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14 Responses to “Bootfitting for Backcountry Ski Touring”

  1. Geewilligers November 30th, 2016 9:07 am


    I’m working my way uphill with a pair of Scarpa Freedom SLs with a pair of surefoot orthotics made for them. After the fitter put the orthotics in the liner he indicated that heat molding the liner would be a “waste of time” due to the fact that they will get packed out faster and that the liner will conform to my feet after 20 or so days on the hill. Is there any merit to this line of argument, or was the gentleman shirking his duties as a duly sworn bootfitter?

    As you may be able to tell, this reasoning was suspect to me at the time, but, as the easy going guy I am, I capitulated. I’m relatively happy with the fit, but do feel there is more heel lift than I’d like. Is this something heat molding the liner would address?

    Thanks for your time and insight.


  2. Lou Dawson 2 November 30th, 2016 9:17 am

    If it takes twenty days of skiing to fit a boot, rather than a boot fitter knowing what they are doing taking an hour, need I really come up with an adjective? I’m afraid o the words I might come up with (smile).

    As for your heel lift, indeed, find another boot fitter who will mold and fit boots rather than lecturing you.


  3. Geewilligers November 30th, 2016 9:44 am

    So, my intuition on these intuitions was correct.

    Can the heel lift be addressed with this liner, or do I need to mentally prepare to get another? There are about 15 days on these boots now (so close to optimal fitting days!).


  4. Lou Dawson 2 November 30th, 2016 10:09 am

    Next time, ask the “boot fitter” if he’s sure it’s 20 days, and not 22.5?

    Heel lift is caused by a combination of factors, sometimes having to do with the shell, not the liner. Only way to tell if you can improve by molding is by doing a mold.

    By the way, if the molding is done with no socks (just thin “stocking” sheath), and you then wear socks for skiing, issues with “packing out” are pretty much taken care of.

    As for the heel lift specifically, in fairness to your boot fitter, I’ve indeed found that sometimes the heat molding process makes it worse, due I believe to the foot moving around and enlarging that area during the heat molding process.

    Biggest thing in evaluating heel lift is try to evaluate while you’re actually skiing, carpet testing can make it feel worse than it is.


  5. Majki December 15th, 2016 3:20 am

    Hi, doeas someone know what should be temperature and heating time for scott PWR lite liners forming? SCOTT doesn’t provide such information and I can’t find it anywhere

  6. Lou Dawson 2 December 15th, 2016 8:28 am

    Hi Majki, I’ve always used my Scarpa blower stack for those, 246 degrees F for 12 minutes. If you’re using a convection oven, probably 240 or even less as the blowers tend to be hot due to external cooling of the bit as it sits there on the stack. Be conservative, you can mold more than once. Or are you using a regular kitchen oven? If so, be super careful with temperature as oven thermometers are sometimes off by quite a bit. Lou

  7. Majki December 16th, 2016 1:20 am

    Thanks Lou. I’m using kitchen oven (but I have one with convection). I successfully molded 2 pairs in the past with it but I didn’t remember what should temperature be and Scott doesn’t provide such info.

  8. Lou Dawson 2 December 16th, 2016 7:15 am

    You might try 230 degrees F at first. 240 F is pretty hot, it’s the molding temperature for Grilamid plastic. I think they use the hotter temps in the blowers, as mentioned above, to compensate for cooling and mixing with ambient air. Lou

  9. majki December 16th, 2016 1:36 pm

    Baked already and it feels good.thanx Lou.
    Best ski site 🙂

  10. Lou Dawson 2 December 16th, 2016 1:42 pm


  11. Dan March 19th, 2018 9:22 pm

    Heya Lou, what are your thoughts (or experience) with baking Atomic Backland shells in a traditional oven? The end goal is to punch out the area around the boney part of the inside of the ankle (medial malleolus) and boney area by the pinky toe. I’ve been searching for info, but all I find is for liners.

    I’m researched enough to know to tape pads to feet in areas to ‘punch’ out, use a liner stocking for a sock, heat oven to 235’ish, use an accurate thermometer in the oven, put the boots on wood covered in foil, preheat the oven for awhile, turn it off after putting them in, and wait 12 minutes with them in there. When taking them out, I’d try to gently manipulate the liners into the shells, put feet in, buckle to normal tightness, stand still 5 minutes, and then put cold packs or freezer bags full of ice water around the boots that cool them.

    That’s my inexperienced understanding of the process. Do you have any insight on whether I’m going to wreck my boots or whether I should do anything differently? My end goal is to heat mold Atomic Backland shells to remove pressure points.

    Thanks, and I really appreciate all the work you put into Wildsnow!

  12. Lou Dawson 2 March 20th, 2018 8:19 am

    Hi Dan, I experimented quite a bit with Backland shell molding, found that at least for me it was way better to selectively punch necessary areas, molding the entire shell is time consuming and I never saw results that were any match for a ring press or boot expander. Doing it yourself in a baking oven sounds risky. I admire and encourage the DIY ethic, but in the case of boot shell modding, it could be better to just acquire the services of a boot fitter. That said, the Backland shell plastic is indeed very heat sensitive, in some cases you can rig up something that presses from the inside, like squeezing in a billiard ball, then hit the punch area with a heat gun. But without prior experience, heat gun can = boot destruction. Lou

  13. Pablo March 20th, 2018 9:41 am

    Lou, What about boiling water methods?
    Maybe Dan can put their backlands on a pot with boiling water.

    As I Know Backlands Memory Fit system needs to heat the shell to 117ºC during 12 min.

    So, I think boiling water could be a safer way to heat shell than a heat gun.

    What do you think about it?

    maybe it worth a try?

  14. Dan April 1st, 2018 10:53 am

    Just a follow up with results related to my comment above. I went to the local ski shop and tried baking the shells without the liners. The shop person padded the dickens out of my hot spots. There was about 1cm+ of firm padding taped to my medial malleulos and fifth metatarsal. The guy added toe caps as well. We used a sock as thin as a stalking. He baked the shells, installed the liner, and I stood in them for what seemed like eternity (30+ minutes). We baked the tongue with the boot, and had the tongue in when I was standing in them for molding. We buckled the boots as I normally would. After standing in them for 20 minutes or so, I asked if they had ice packs to cool them down with. The guy produced some Fischer branded ice packs that are shaped for the boots. We cooled the boots for even longer with those on, and then I finally took them off. After removing the firm foam padding taped to my feet, I put the boots back on and walked around in them. There was noticeable relief!

    I’ve spent the prior 5 days touring in the boots and am happy to report a significant improvement in comfort. The boots no longer hurt at all in uphill mode, and there is only mild discomfort in downhill mode.

    It seems baking the shells+tongues and using a ton of firm foam padding solved my fit problems with the Atomic Backland!

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