Sven Coomer, Founder of Zipfit Ski Boot Liners (Ep.35)

What is the least understood but arguably most important piece of ski equipment?

Ski boot liners.

While ski boots — that is, ski boot shells — get a ton of attention, liners get almost none, and many, many skiers who are having issues with their boots, are actually having issues that could be solved with the right liner.

This past week I was in Aspen Colorado at the World Cup Finals of ski racing, and that presented the perfect opportunity to visit the home and the workshop of Sven Coomer, the founder of Zipfit ski boot liners — or “Inner Boots,” as Sven prefers to call them.

When it comes to skiing, Sven has seen it all, and he has personally played a significant role in a lot of it.

Sven Coomer, Zipfit Boot Liners on the Blister Podcast
Sven Coomer in his workshop in Aspen, Colorado. (photo by Jonathan Ellsworth)

Sven began designing ski boots for Nordica in 1969, and he worked on one of the last leather ski boots (the Nordica Sapporo — which I saw in his workshop, and it is gorgeous – we’ll include photos in the show notes to this episode). After the Sapporo, Sven then designed Nordica’s first plastic boot, the “Olympic.”

Sven was born in Sydney, Australia, and he competed for Australia in the Modern Pentathlon at the 1956 Melbourne Olympics. Truth is, there’s so much to Sven’s history that I’m just going to refer you to his bio at, where it will then become clearer to you how significant of a role he has played in the history of ski boots and ski boot liners.

Today, there are many skiers who wouldn’t think of skiing in anything other than one of Sven’s Zipfits, so we’re going to try to get a clearer sense of why that is the case, what makes Zipfits different, why boot liners don’t receive the attention they deserve, and why Sven believes that liners are the single most important piece of ski equipment.


  • Why “Liners” should be called “Inner Boots,” and what a good inner boot should do (0:00)
  • Why Sven thinks that liners are the most important piece of equipment (5:00)
  • What is someone failing to understand if they are failing to consider the inner boot? (13:00)
  • Why liners and boots are more complex than skis
  • Why Zipfit liners don’t pack out (22:50)
  • What is it about the construction of a Zipfit liner that’s different? (24:45)
  • What are the top issues / problems that a Zipfit liner might solve? (29:00)
  • Alpine-Touring boots & liners — and the touring inner boot that Sven is working on (39:20)
  • Final thoughts on the difference that the right liner can make (49:30)


  • The Nordica Sapporo, Nordica’s last leather boot:
Sven Coomer, Zipfit Boot Liners on the Blister Podcast
Nordica Sapporo

17 comments on “Sven Coomer, Founder of Zipfit Ski Boot Liners (Ep.35)”

  1. I’ve skied the zipfit for years. My bootfitter, a collaborator of Sven’s, always looks at me like I’m crazy when I say my feet get cold. I don’t get cold in my AT set up with an intuition liner and it isn’t a circulation issue.

    any thoughts?

    • I moved to zipfits this season. Toes were always warm with intuition, never with stock. They are not warm at all with zipfits. I have hot tronics and they are a pain in the butt. Next season I’ll try the Lenz heated socks

    • It would be nice to have easy access the the cork. I can say without a doubt this liner has let me ski with the most heel hold I’ve ever had. In saying that, I’ve used 2 tubes already in my World Cup liners and have two more I will inject soon. I have a friend with the Grand Prix who’s put 4 tubes in his pair.

      Perhaps we both poorly fit out shells? Or perhaps our shells have large pockets of free space.

      While the material doesn’t “pack out” it certainly does move. So while I don’t believe my pair has packed out in the least bit, the cork material has moved to fill the voids, leaving more room than I want. Quick fix to add more cork and have it right once again.

  2. My zipfits are warm and have improved the comfort and performance of my lange rs 130’s considerably. Highly recommended, especially for hard to fit feet.

  3. 1500 days in one pair of these?, did I hear that correctly? I’ve got to listen to this again. Your on the mountain in them Jonathan, how about a little quick post-podcast feedback?

  4. Great podcast! Jonathan – do you think that these could add enough stiffness to bring a pair of Salomon Quest Max 130s up to the stiffness of a more typical 130? I’m a bigger guy (6’5, 205 lb), and I’m beating the hell out of my ankles (outer, front portion/talus) every time I over-flex these boots.

    • Hmmm, I haven’t skied the Quest Max 130s, so I don’t know how far off from a “more typical 130” it currently is.

      But in Marshal Olson’s Zipfit review, he said that he felt the Zipfits made his boots about 10% stiffer … and that seems roughly correct to me. I’d say there is a touch of additional stiffness … but the biggest thing to me so far is the very snug, precision fit, and the zero — zero — heel movement…

      • Thanks for answering the question I should’ve asked: “Do you agree with Marshal’s opinion on added stiffness?” I see Zipfits in my future.

        • Hi, David – apologies that I missed your follow up question. But I believe I answered it in my original response? So again, “I’d say there is a touch of additional stiffness,” but I don’t know if I personally found it to represent a jump up from 130 to 140. Rather, what I found to be the case is that, particularly in very warm weather, the Zipfits kept my HEAD Raptors feeling like a true 130, and not (in warm temps) having them feel way too soft & collapsible, as if I was in a 110 or something.

  5. Zero heel movement – that’s enough for me. Sorry Lange, no new boots this time, sorry intuition, no new liners.

    Jonathan, are you finding that it may be possible that while running stiffer with the liner you could indeed run a softer shell for increased range of motion? Sven talks about this, That would be a dream without boot transition turning to mush.

  6. Hi Blister, I’ve a pair of Salomon S-lab mtns that I really like but after a season and a half in them I’m thinking of swapping out the stock liners for a little more support and heel hold. I’ve been waiting to hear the exciting news that you teased to come from zip-fit. Is it still on the way? Should I hold on or just get the existing tour liners?
    I’m still happy with the mtns and am happy to wait until next season if the upgrade is worth it.
    Great work as always guys and girls.

    • Hi, Matthew – we haven’t received any updates, so I think you should go ahead with the current tour liners. I just checked those out again last week, and I really very badly want to get in a pair. They are gorgeous and substantial, which probably won’t be of interest for those who tend to complain about walkability / ROM (which isn’t me), but for those of us looking for good (not best-in-class) walkability and outstanding downhill performance … well, as I said, seeing this liner again last weekend has me very eager.

  7. Is there no anyone around with experience from (well made) Strolz inner boots and Zipfit?
    I’m a full time patroller since 18yers. Strolz is currently the only solution that have worked for me. Including srveral efforts of foam injection liners from Surefoot (gass pockets) and Sidas (to spongy) and even a few failed attempts with Strolz. Stock Intuitions have not been close to be even skiable for my somehow strong but bony feet and instep with a left foot that tends to probate so much so it’s ~8mm longer due to the lower arch.
    I more have a pair of Zipfit Sidewinder World cup wich I have had fired in heated up plug shells and tried on a coupe of times. To painful to ski in due to pressure points. I have concluded I need to fill them up to have a chance to have the contours around my knuckles.
    Even my now worn out Strolz are far more comfortable and supportive even they now have lost the vice like heel grip they given the first ~200-300 days or so until they now are cause aching pressure on my knuckles and needs to be buckle very tight to be any good to ski in, wich causes my feet by to go numb.
    Can I count on the Zipfit to become as supportive as fresh Strolz? Or should I expect less close perfect mold and evenly pressure and heel grip?

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