Bootomania — Getting Thermo Liners to Fit for Backcountry Skiing

Post by blogger | December 28, 2006      

If your backcountry skiing boots fit out of the box, you are blessed. If they heat mold and fit good you’re okay — or? I’ve had quite a bit of trouble with heat mold liners over the years. They never get snug enough around my ankle and seem to shrink and become more roomy once they cool after molding.

Backcountry skiing boot liners.
Victims of cruel experimental exploitation.

A few months ago we got a convection oven specifically for boot molding. I cooked a few liners as test boots came in and was never totally happy with the results. So a few days ago I went crazy and molded five pairs of liners for the same pair of shells, and experimented with how to get the things snug.

Molding without socks was a no-brainer to get a tighter fit, but doing so didn’t totally solve the problem. Next step was to eliminate the toe cap that shims the liner out while molding so you get more toe room. Instead, I just taped a wad of duct tape on the end of my big toe, put a spacer between little toe and the one next to it, and called it good. Huge difference. Turned out even the standard toe cap was causing my boots to mold with way too much room in the front. (Proceed with care if you try this, as the toe area can end up too tight and you’ll get cold feet or bruised toenails. Mine are almost too tight, but are packing out with use.)

Next, how to get the overall fit tighter? My theory was that my liners were getting “over molded,” in effect being packed out before even skiing them. I did a couple of things to prevent this, and it all worked. First, I slowed down a bit when transferring the liner from the oven to the boot and getting my foot into the boot, on the notion that allowing the liner to cool off a bit would prevent it from getting so squished. No need to hurry as I’d been taught for years by boot fitters. Next, I only kept my bare foot in the boot and hot liner for two or three minutes, and after removing my foot I immediately yanked the liner from the shell so it wouldn’t sit there getting packed in by the shell as it cooled.

Tips: Wearing garden/work gloves (ones with the little grippy rubber buttons on the palm) helps you manipulate the hot liners with confidence, and prevents scrapes and cuts while arranging the liner in the boot so the overlap is correct. If fitting with bare feet, use foot powder or a nylon stocking foot on your feet so they slide into the heated liners without catching.

Prior to this, I’ve been snugging up my liners by spot blasting with a heat gun. I’ve had mixed results with this, and it’s bad for the liners because it uses up your heat/mold/cool cycles. I still ended up heat gunning the ankle area of my newly molded liners, but the need for this was minimal compared to past moldings.

In all, a fun rest day after three backcountry ski days in a row — and now my boots fit better!

Boot model note: I was fitting a pair of Scarpa Matrix. While molding I noticed my thicker left leg (it was broken, long story) ended up with more forward lean than my skinny right leg. I’d noticed this while skiing, and had thought about correcting with a shim behind my calf. The Matrix has adjustable forward lean. A few turns with a hex wrench, and my legs are in harmony. This fine tuned forward lean is a nicely executed and truly excellent feature of Scarpa AT backcountry skiing boots.


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39 Responses to “Bootomania — Getting Thermo Liners to Fit for Backcountry Skiing”

  1. Chase December 28th, 2006 6:58 am

    Hey Lou,
    I bought my Garmont Adrenalins last winter
    and heated up the liners many times.Could
    not get them to fit right. So I
    threw them away. Next I took my Nordica
    liners and did some surgury to them and
    put them in my alpine touring boots. Best
    fitting boot I have ever had. I have the stability
    of a true alpine boot but yet can tour in them
    very comfortably. Guess you just have to think
    out of the box.

  2. Wesley Bunch December 28th, 2006 8:05 am

    Hi Lou,

    Hey I think the best trick after years of tweaking is NOT to use the traditional convection oven! Instead one of the heaters that only blows hot air into the interior of the liner works best. It allows the interior of the liner to mold to the foot and the exterior of the liner to slowly change to the interior volume of the shell with use. I also recommend not using a toe cap and going barefoot. Remember these liners are not going to get tighter. They will “pack out ” after a dozen days or so of use. Also consider the thickness of the liners. The Garmont Omni seems to have a millimeter or so more foam, as does the Scarpa liners. These will work best for low volume feet. Garmont G-fit liners work best with people who have wide or high volume feet. Volume is the most overlooked fitting trait in my opinion.—-Wes

  3. Shane December 28th, 2006 8:47 am

    Do all liners take the same temp/time to heat properly? I have a pair of snowboard boots that I’d might like to cook myself. I do have a gas convenction oven but I’m not sure what temp or length of time to use.

    Also, the boots fit nicely right now except for a little bit too much pressure on the outside bottom of my left foot – this has been the case with most of my boots. Do you think it’s worth taking the chance of making the fit worse just to fix that one area?

  4. Lou December 28th, 2006 9:01 am

    Shane, in my experience the temperature range that works for molding is pretty broad. During this last test I heated them all at 250 degrees for about 10 minutes. For time I go with clock but also visual, seeing when they’re puffed out. Use an oven thermometer in the convection oven to make sure you’ve got the temperature correct. If in doubt, get the specified molding temp from the maker before you start.

    As for your particular case, I’d not re-mold the entire liner. First work with your footbeds, and if necessary spot mold the liner with a boot press at a shop. In the case of pressure at the bottom of the foot, it’s usually cured by grinding away a bit of footbed material.

    ‘best, Lou

  5. wolfy December 28th, 2006 2:36 pm

    It looks like you’ve applied some material to the outside of one of your boots. What material might that be? I’m thinking of a way to use something to mellow out a hot spot on my non-moldable alpine boots the way you would use Mole-skin on a blister.


  6. Lou December 28th, 2006 8:19 pm

    Boot fitters use a variety of glue-on foam. It comes in various densities. I don’t know the source. I get it from the boot fitter. You just glue it on with Barge cement then grind it down to fit.

    If you’ve got a pressure spot in a non-mold alpine liner. Just grind away at the outside of the liner with a disk or drum sander, then cover the wound with duct tape. Works like a charm. Done it a hundred times.

  7. Lou December 28th, 2006 8:27 pm

    Nice mod Chase!

  8. Kevin December 28th, 2006 10:15 pm

    What liners take up the most volume. It seems to me the dynafit and scarpa liners puff up much more than a garmont? Have you tried intuition liners?

  9. Chris December 28th, 2006 10:18 pm


    Of all the liners you used which one gave you the fit you were most happy with – and why? Also, did any of them have any annoying characteristics – like drastic shrinkage. Just curious…


  10. Lou December 29th, 2006 6:25 am

    Kevin, the only liners I’ve found that really work for me in terms of stiffness, height and filling volume are the black Scarpa liners as found in the Spirit 3. I use this liner in all my backcountry skiing boots. Many if not most people do fine with the liners sold with their choice in AT boots, but I’ve got skinny sensitive feet, and spend many days in my boots over 6 or more months every ski season, so I’m super picky and really notice the difference between liners and different fits.

    Many of the thermo liners are too soft for me, and many of them are too low cut around the shin to make a smooth transition from the boot shell to my leg.

    The liners in the photo with the blue foam glued on are the Scarpas I like. The blue foam was something I tried for my skinny ankles before I figured out how to get more volume out of the mold by using the methods I wrote about in this blog post. The blue foam compressed and shrank when I re-molded, so it now does little but look ghastly.

  11. Lou December 29th, 2006 6:35 am

    Chris, I’m thinking that what I usually think of as liner shrinkage is actually the liner packing out when molded too aggressively (hot liner with foot inside for a long time). As for annoying, a couple of things keep bugging me. Many liners are so short they barely extend beyond the top of the boot shell. This can result in an uncomfortable transition from boot to shin and calf (but people with big calf muscles might feel the opposite). Some liners seem to be lower density foam and not offer support that help the boot feel more beefy. This makes the boot tour more comfortably and is thus probably a compromise and not something to pan a boot over. The Scarpa Matrix liner is soft and low cut.

    Personally I like the wrap-around liners much better than those with tongues. With my skinny legs, I end up with too much slack/space in the tongue area and have to fill it with a wedge shaped chunk of foam (known as a “duckbill” to some boot fitters). Just another hassle I prefer to eliminate.

    Biggest gripe with thermo liners is how hot and sweaty they are if you’ve got warm feet with good circulation. Someone needs to invent a liner that breaths better. My feet actually got so hot and sweaty they hurt on warm spring days. I’ve gotten so desperate I’ve poked a bunch of holes in the liner with a knife.

    All liners can be swapped around, and anyone with fit or performance problems should experiment.

  12. justin December 29th, 2006 8:32 am

    In response to someones question about taking up volume, Intuitions take up as much (if not more) volume than Scarpas, but seem to be harder to mold well in my opinion. They also make the stiffest thermo liners out there (as well as some softer ones), which some people find too stiff for touring. Has everyone had the best luck with standing while molding? I have stood and sat during molding, standing obviously recreates the shape of your foot while skinning/skiing better, but I think it might allow the liners to puff up more.

  13. Lou December 29th, 2006 8:46 am

    Thanks for the input Justin.

    I’ve found I have to stand while molding, otherwise my footbed just doesn’t feel right. But I try to stand STILL so I don’t wriggle my foot around and pack out the liner. Other than whacking my boot heel on the floor a few times to seat my heel.

  14. Jan Wellford December 29th, 2006 7:36 pm

    Lou, this is a great post, and awesome comments from everyone else too. Time to start experimenting. One question Lou: by “slowed down a bit” when removing the liner from the oven, do you mean just a few second, or more like a minute, or even more? I’ve noticed that even 10 or 15 extra seconds seems to make the liner stiffer before shoving it in the boot, but was wondering how long you were waiting in your successful trials?

    Also, I’ll second Justin’s experience with Intuitions. We used to use Intuitions in mountaineering boots, and they were definitely stiffer and harder to mold properly than the Scarpa low liners we use now.

  15. Lou December 29th, 2006 7:44 pm

    Hi Jan,
    I mean a few seconds. Just staying on the good side of panic mode (grin).

  16. Darin January 4th, 2007 10:24 pm

    Hi Lou. First, I think you’re site is awesome. Lots of good info for newbies. Just wanted to say that I followed your molding instructions and it worked out great, and I’ll be the first to tell you that I’m not the smartest guy around. I don’t know how it could have been easier. Without your instructions, I would have been lost. Newbies should be comfortable following your instructions. By the way, I used a standard cooking oven with the wood and tinfoil with no issues.

  17. Luc Bernier February 12th, 2007 9:11 am

    Hello Lou, thanks for the help you give to backcountry skiers.
    I had to order boots by mail. 26.5 Scarpa spirit. I’m used to thight fitting alpine boots size 26 . I feel my new boots not to be thight enough. I’m affraid they even get loose after they pack out. I’ve not molded the boots yet. What shoul I do ;return the boots or thermo-form them.
    Thanks !

  18. Lou February 12th, 2007 11:13 am

    Hi Luc, first, I’d call customer service where you bought the boots, and see if the Scarpa shell for 26.5 is the same as 26. If that’s the case, go ahead and mold the liners. Most people do better if they get their touring boots a half size or so larger than their alpine boots, and mold with room in front of the toes, but snug around ankle and forefoot.

    If the Scarpa shell break means your size 26.5 is next shell size up from 26, then you may need to return the boots and mold a 26 for a snug fit.

    If you need boots that keep your toes warm, such as for touring in Colorado, Montana, Wyoming, etc. you need to be careful not to mold the toe area too small.

  19. Luc Bernier February 13th, 2007 11:39 am

    Thanks Lou, I ordered a 26 which is a smaller shell. I’ll see.
    Can I get a more snug fit after thermo-molding (using your method )or will it make the boot necessarily bigger ?
    Since I’m in Canada, I have to be carefull about the cold.
    I use to have Garmont Dynamite 26.5 wich were too thight.
    Thanks !

  20. Ken Gross May 9th, 2007 1:49 pm

    Hey Lou,

    Couple quick questions for you: When you pull the liner out of the oven, do you first put your footbed into it and then your foot in the liner, and then foot+Liner into Shell? Could you elaborate on your toe cap? In your post it sounds like you are just wrapping a little bit of duct tape around your toes. Thanks!

  21. Lou May 9th, 2007 2:02 pm

    Hi Ken, yeah, you put the footbed in the liner, then your foot in the liner, then foot/liner into shell. Use some talc powder to help it slip in. Another method is to put your foot and footbed inside a woman’s stocking before insertion into liner. Experiment.

    For toes we’re using duct tape, then a couple of toe sections we cut out of old socks.

    ‘best, Lou

  22. Ken Gross May 10th, 2007 2:25 pm

    Hi Lou,
    Thanks for the clarification! I’ll give it a go! Got some funny looks at the Target in Silverthorne when I bought a pair of pantyhose! 🙂 I am going to Janets tommorow for a couple nights, and I’ll be skining up in my newly molded thermoliners!! Have a great weekend!

  23. Jason Hendrickson December 12th, 2007 3:47 pm

    Let’s see if I can breathe some more life into this old posting and keep it going for a bit. 🙂 I have a pair of new Spirit 4’s with the Intuition liners. I want to try molding them like you’ve suggested, but I’ll have to use my regular kitchen oven. My biggest concern is whether I would need to hang them in the oven somehow, or if I could just set them in there. Would I melt them if they touched the sides or the rack, since the metal is bound to be hotter than the air?

  24. Lou December 12th, 2007 4:46 pm

    Jason, people recommend that what you do is pre-heat the oven just to the required temp, then turn it off just after you put the boots in. The metal in the oven should be the same temp as the air inside, if your pre-heat for a nice long time. Set the liners on a sheet of aluminum foil as well. When I use a regular oven I actually do not worry about turning off the oven, I just use an insulated two layer cookie sheet under the liners, so any problems with radiant heat scorching are blocked by that. Main thing is to use a good thermometer, as over-heating can ruin the liners real fast.

  25. Gunnar Vangberg December 18th, 2007 12:44 pm

    HEllo, Great site!
    I just got a pair of Dynafit Zzero4 cf size 27. Before heat molding I can feel my toes barely touching the front. If I do the molding properly by taping my toes and adding the toe of a sock, will this make the liners fit, or should I go for 27,5? They are the same size shell.

  26. Lou December 18th, 2007 2:30 pm

    Gunnar, I’d go for the 27.5 if possible, that way you’ll get a better mold in terms of length for mountaineering (room for toes.)

  27. Dimitar January 31st, 2008 4:38 am

    Hi Lou,
    first thanks for the great site and the posts – I visit almost daily.
    I am having an issue with fitting my Dynafit Zzero’s (carbon version). I got 28, maybe it was a bit bigger, but usually I don’t fit in 27/27.5 and here (I live in Bulgaria) I had the chance only to pre-order them without trying.
    So, 28 was my only changes, I got them, molded as per your instructions here. Everything is fine, feel, fit in the toe area, ankle, skiing, skinning, stiffness, etc.
    The only issue I have is the heel area – when skiing and all buckles really closed tight, I can still lift my heel, if I try, may be up to 5mm. May be it is not that big deal, but it brings the over feeling of the boots as being not tight and insecure.
    When skinning it is a lot more, and my heels start to feel bad due to the friction.
    As I have started using the boots only several weeks ago, now I am afraid that it gets worse and worse.
    Unfortunately, here boot fitting is not very popular at all and I don’t think I can find a boot fitter to help me.
    Any advice, how I can solve this heel issue?
    Thanks a lot in advance!

  28. Lou January 31st, 2008 9:21 am

    Dimitar, sounds like you might have gotten too large a shell. Solutions? Return the boots and order the smaller shell. If that doesn’t work, return again, get larger shell, then build up volume on liner with glue-on foam. Or change boot brands. Without time consuming and professional boot fitting, not every person can get a perfect fit in one brand.

  29. Mike April 23rd, 2008 1:50 pm

    Hi Lou –

    I just wanted to pass along my thanks. I purchased my first pair of AT boots (Garmont Mega Rides) this week and used your instructions to heat them at home. Everything worked great. Thanks as well for for all of the other helpful info on your site.

  30. Alex October 19th, 2008 1:17 pm

    Lou, Greetings and salutations, how does one measure volume what determines higk volume or low volume? Is this measured during shell fit? Also I have currntly a pair of Garmont Adrenilines 3 seasons old and getting packed out I have also added a PowerBooster strap for increased stiffness in the boot to counter a fairly light flex in Alpine mode. My interest is in Black Diamonds new A.T. line Factor or Method. However I think the 130 Flex of the Factor may be to great vs. the 110 of the Method. My question concerns the BOA system in the B.D. liner how does this effect liner fitting is this liner still heat moldable? If so would you leave the BOA system loose and simply heatmold fit and fine tune with the BOA system after ski days to counter pack out? Also is this a stiffer skiing boot than the Adrenaline? thanks in advance aloha. Alex

  31. Sawyer December 6th, 2008 2:04 pm

    i just got a pair of Spirit 4’s, did the molding last night. we took them out of the oven and immediately through my feet into them and then into the shells. after about 10 minutes of cooling i began to walk around. the left boot was great, but in the right i found there to be a pressure point the size of a silver dollar pressing into my right shin muscle. i am debating a swift return and getting something different. the thought of recooking them has also been tossed around. the intuition liner seem pretty thing to me, having never owner the wrap-around before. i want these to work, but can’t bear the thought of calling my season of the count of skin-bang!

  32. Lou December 7th, 2008 4:12 pm

    Sawyer, you can mold those a number of times. Re-mold. If you have a pressure spot, build a spacer on your foot in that place before you mold, I usually do that by cutting some cardboard or foam I have laying around and taping to my foot with some duct tape during the molding.

  33. Adam December 23rd, 2008 11:20 am

    Hey Lou,
    what temp do I set my oven at for the Garmont Endorphins?

  34. BigD October 25th, 2009 7:52 pm


    After cooking, I feel like I need a skoosh more room in length in my liner toe box. They are fine while in motion – the up and down – but while standing, my toes are tight against the end of liner. Afraid of losing a toe nail if I have to hike for an extended period. Granted, I have only used them on a couple short trips so far.

    Should I tinker with the fit, or see if they will pack out some? If you recommend adjustment, what are your suggestions? I seem to have plenty of room in the shell and don’t want to re-cook the entire liner if I can avoid it.

    Thanks ahead.

  35. Lou October 25th, 2009 8:11 pm

    BigD, what I do in that situation is try using a boot press rather then re-molding. Sometimes I just work on the liner out of the boot. Sometimes I leave it in the boot… Sometimes it just takes a tiny bit more space to make it perfect. Also remember that all liners pack out, so if you can use them for a few days without wrecking your toenails, it’s worth trying to just wear ’em in.

  36. Christine Byl November 10th, 2009 3:48 pm

    Very helpful stuff as I’m reading, thanks. Sorry to duplicate a little, but I want to be sure I get this right. I bought a pair of used Scarpa T2Xs at a ski swap, in great shape, $150 bucks. The liner fit is not great, with someone else’s heel imprint, and tight toes, but the shell size seems perfect, and I tried another pair of used Scarpas, same size liner (25,5), that had clearly been on a much bigger foot, and it was roomy on me, so I know the right fit is possible for me somewhere between these two. The trouble is, getting it!

    I want to try it at home, since I live far from a shop and it’s $60. So, I’ll try the pre-heat and turn off method (no convection stove). My main concern is getting enough toe room without sacrificing performance. I live in Alaska and ski in brutally cold temps a lot. One reason I got new boots was because my old T3s were too tight and I have constant frost nip, especially on overnight trips. I have another pair of old Garmont Liberos that I use for really cold (20 below or less) so I can get extra socks in, but they are really too big and quite sloppy. So, these T2Xs are supposed to replace both–good enough for cranking on area once in a while, but mostly, warm enough and comfy enough for the bulk of my skiing which is cold and backcountry. Any tips for a roomy toe box but not too loose an overall fit would be appreciated!

    Hope this all makes sense, sorry so long.

    AK Tele Girl

  37. Christine November 11th, 2009 2:00 pm

    Just checking in on my previous comment, posted yesterday about boot liner fitting. Any input?

  38. Lee November 11th, 2009 3:00 pm

    I’m no expert but I suffer from cold feet a lot. With thermo fit inner boots I used to put a bit of thin foam between each of my toes and then put the cut of end of a thick sock on over my regular ski socks for forming…I still got cold feet. Read about someone taping the veins on their foot as well…tried this and it seems to help a bit (or maybe it wasn’t such a cold winter that year?).

    Anyhow eventually I ditched thermo fit inners and got a pair of regular inners (dynafits) which fit better, are beautifully made, much more robust and a damned sight warmer! Problem solved – for me anyway.

  39. Lou November 11th, 2009 4:44 pm

    I’ve never felt like room around the toes was much of a detriment to performance, but then, I’m not talking about telemark fitting… I do know that key is to indeed use toe caps but to also taper the larger box back to your performance fit in the instep and ankle area. It’s also super important to have a long enough boot, so you end up with full thickness of thermo foam in front of your toes, and your toes are not pressing against the end.

    As for molding yourself, I’d do it with the help of a bootfitter the first time if you’ve never had it done before, just so you know what to expect if the process is done correctly.

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