WildSnow Dynafit Lab — Homework Handed In

Post by WildSnow.com blogger | March 29, 2010      

All this talk of Dynafit toes opening while skiing got me curious. After seeing the way ATK provides configurable tension in their toe unit by inserting small disk shaped springs, I got to thinking, could a similar mod be done to a Dynafit binding? And just how much could the binding to closing force be increased? (Disclaimer: This is only an instructive experiment, not a recommended modification due to unknown wear and the increased and possibly dangerous release tension this mod would create.)

Dynafit binding toe modification

Experimental Dynafit binding toe modification, arrows point to added washers that nearly doubled the closing force of the toe wings. Click image to enlarge.

So, at least sometimes, after fantasy comes action. My feet seemed to have a mind of their own as they walked me out to the mod shop. My hands seemed to instinctually find the pin punch to remove the touring lock on an old pair of classic TLT toes I had laying around. Somehow, washers of nearly the right size were found in my parts bin, though the side of one in each pair had to be clearanced so they’d fit side-by-side. I was rewarded by a nice adrenaline rush when my first experiment flew apart and went ballistic, nearly taking out the snowmobile headlight behind me. And finally, with a modified and functional toe assembled, it was amazing how after using a pair of vice grips as a lever arm I was able to compare the spring force of the modified and un-modified toe, using a luggage scale max weight memory as a dynamometer. Result: sticking the washers in there nearly doubled the amount of force it took to open the toe.

Dynafit toe modifications

Dynafit toe modifications

Dynafit backcountry skiing.

Using a luggage scale as a dynamometer, key is I added a long lever arm to the binding using a pair of vice grip pliers.

Okay, if anything this little exercise might give all of you a better idea of what keeps that binding closed on your foot, and how those forces could vary. As for increasing this force in the binding retail version, like any machinery design change this would involved consequences. For starters I’d imagine more closing force would cause more wear on the boot toe fittings and the binding pins. It would also require re-calibrating all the lateral release tension numbers and perhaps even changing the lateral release mechanicals in the heel unit of the binding. Expensive stuff for the manufacturer. But you never know, we’ll see what happens over the next few years.

Note: One valuable thing I learned from this experiment is that the small green (other colors on other models) plastic parts do show some wear after lots of binding use. Wear or manufacturing size variations in these parts could reduce the amount of toe wing tension. Prior to recently, I’ve concentrated most of my seat-of-pants engineering on the Dynafit heel unit, fun to shift the microscope over the the toe.


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31 Responses to “WildSnow Dynafit Lab — Homework Handed In”

  1. Jordan March 29th, 2010 9:52 am

    Good that you provide the disclaimer of not recommended, as this seems like a potentially useful mod for us heavy guys.

  2. Lou March 29th, 2010 10:35 am

    Someone will be out skiing with this mod, I have a strange feeling.

  3. Bill March 29th, 2010 10:52 am

    One of the issues you have to look at is overstressing the springs. They are designed to work in a certain range. Compressing them more can reduce the life of the spring significantly, not to mension mating components.
    I wish Dynafit would make models designed to work in specific Din ranges to help cover lighter and heavier individuals better. This would include different toes. With such a large distrubution this does not seem a difficult task.

  4. Lou March 29th, 2010 11:45 am

    Bill, exactly, that’s why this was an experiment not something I’d ever recommend. Besides, it’s not exactly easy taking the binding toe apart and re riveting the touring lock, etc. And like I said in post, I’m not even sure the binding is strong enough to take the added pressure.

  5. Knappen March 29th, 2010 11:56 am

    Nice test! Your concern of added wear of the inserts and pins is probably not an issue though. The locking lever in touring mode probably exerts more force than the spring modification does. As for your other concerns, I can only agree.

  6. Randonnee March 29th, 2010 11:56 am

    New toe pieces eg FT, ST, compared to older may offer some clues as well.. It seems to me that spring strength is just part of the total picture.

    Ski width is another consideration. My new ST Pro (unlocked toe) on Seven Summit Superlight holds my 100+ kg in on high speed carve on firm and hard snow, in chutes, small air etc. My FT12 on Manaslu unlocked toe holds while skiing soft snow.With the FT12 or ST Pro fully-locked when I traverse while skinning onto hard wind crust or hard refrozen while touring I get instant toe release sometimes.

    My observation and practice also shows that the skier technique will cause Dynafit toe release. I developed a style to stay in the toes on hard steep snow, and I have observed guys of normal weight ski out of their toes while skiing beside me on chattery-snow, when I did not.

    Lou could start another website dedicated to Dynafit toes! 🙂

  7. gonzoskijohnny March 29th, 2010 2:02 pm

    I commonly ski with toes one click up, maybe a poor man’s version of your toe spring pre-load shim mod. I can still lateral twist out readily in carpet testing (and snow proven in late PM breakable ice over slush with a tree avoidance hockey stop at vail pass recently :w00t: ), so lateral release must not be changed much, Vert release upward from heel is obviously unchanged (i ski DIN 5.5-6, 160 lbs + pack). When the occasional pure vertical heel release does happen in nasty breakable crust, my toe will stay in at one click, and I can step back into the binding while skiing. Maybe complications from forward twisting falls?
    BTW- way cool neon pink toe lock lever- where can i find some? Any particular vintage?

  8. Njord March 29th, 2010 2:42 pm

    Is the tape on the fingers from the first failed experiment?


  9. Lou March 29th, 2010 5:01 pm

    A different failed experiment (grin).

  10. Mark W March 29th, 2010 6:58 pm

    I broke a binding once and was loaned a pair of skis with Salomon race bindings that had half a roll of pennies in each toepiece to increase DIN. Can you say DIN 40? Scary indeed.

  11. Sean Lohr March 29th, 2010 7:37 pm

    I bet the TGR crowd is really gonna like this one.

  12. Lou March 29th, 2010 7:37 pm

    Indeed, and did anyone notice the washer in the spring barrel of the FT12? Shimming springs with washers is not exactly a new thing…

  13. SteveG March 29th, 2010 8:01 pm

    With my relatively limited time on the Comforts, I’ve only come out of the toe once and that was inbounds on frozen corduroy at minus 10 deg. Like skiing on a quonset hut. A fluke? The real proof would be for someone with a chronic problem to try some shims and see if it helps. Perhaps the proper sized “C” clips could be inserted for testing as disassembly would not be required.

  14. Lou March 29th, 2010 8:10 pm

    Steve, interesting point on the C-clips, I’ll try that!

  15. SteveG March 29th, 2010 8:42 pm

    Just an untested thought. Would have tried it myself but don’t have and C clips lying around. You may or may not have to clip off the center “pip” to get a fit. As I don’t get to ski as much as I would like I fill the void with Dynafiddling. Hence the 20 spring cup removals in 12 months that I mentioned earlier.

  16. Jack March 29th, 2010 9:02 pm

    Lou, thanks for the thoughtful testing of the Dynafit toe binding. Well done! Does the dimension between the pins change with the increased spring compression via the washers?

  17. Walt March 29th, 2010 10:34 pm

    Yeah, Lou… you are like a genius when it comes to all this mechanical tinkering stuff. But what is to keep the washers from falling off? That would be a really fine, small weld that is beyond the capability of a lot of welders.

  18. Lou March 30th, 2010 7:24 am

    Walt, as shown in the photo there is a nib/pin inside the springs, the washer is on that, it can’t come off just like the springs can’t come off. Remember this is an experiment not something people should be doing to their bindings.

  19. Lou March 30th, 2010 10:22 am

    Jack, no, the dimension is set by how the mechanicals work together when opening and closing the binding.

  20. Jonathan Shefftz March 30th, 2010 2:06 pm

    “Vert release upward from heel is obviously unchanged (i ski DIN 5.5-6, 160 lbs + pack).”
    — I’m amazed that anyone of that weight can stay in any binding (alpine downhill or AT) at those settings (unless the bsl is really long), since up to a 310mm bsl for a Type 3 skier is 8.

  21. Tony March 30th, 2010 4:53 pm

    Dynafit related thread drift : anyone know why the manaslu & stoke inserts are warrantied only for vertical/comfort & not the speed? Mounting pattern is the same, so why the specific exclusion? Not enough fore-aft adjustment range in the speeds, thus making the inserts a little less useful? Still don’t see why that would compromise warranty.

  22. Jonathan Shefftz March 30th, 2010 4:55 pm

    “Not enough fore-aft adjustment range in the speeds, thus making the inserts a little less useful?”
    — I have two friends who got lucky with their BSL & ski length combo for mounting Speeds on Manaslu, but won’t work for many (most?) combos, thereby necessitating mounting a Speed binding outside the inserts.

  23. Craig March 30th, 2010 6:43 pm

    Interesting info about the Manaslu and Stoke. I am agonizing over which pair to get. The one thing that was mentioned to me by a retail shop was the fit issue. I wonder if they knew about the warranty exclusion. Manaslus seem to be a better ski for all around – but the early rise in the Stokes and a little wider under foot has my attention – especially today with the late year powder blast of 16″ here in Washington. Hmmmm….

  24. Rob M March 30th, 2010 8:11 pm


    The Manaslu has been my soft snow ski for two seasons. I would not call it all-around by any stretch. Manaslu is way fun, mine feel very soft and I thread trees easily on them in powder. I think Manaslu feels pretty insecure on hard slick Cascade snow. I am happy to be back on my Seven Summit Superlight lately for hard snow and corn. Here is my discussion of Manaslu http://www.wildsnow.com/1733/robs-dynafit-manaslu-guest-blog/

    Stoke may be better for a big guy like me so I am anxious to try them. I have some Stoke in a box but cannot ski until May due to an injury and MD orders.

    I still do not get how wide skis work well on hard snow, but I am over 50 and have skied a lot on skinny skis.

  25. John March 30th, 2010 8:48 pm

    I have to admit I am kind of gear-head, but have a designer of high performance products in a number of sports, and a life long skier.

    I have a pair of both the Manaslu 187 and Stoke 182. The Manaslu is really light and versatile, great for long tours, but not what I consider to be a “high performance” fun ski.

    The Stoke performs well in powder and has amazing edge hold on melt/freeze snow. It even carves well on corduroy! The Stoke has more durable edges/sidewalls as well. An extremely versatile ski!

    Been on the rocks with both. Stokes win in the durability category.

    So, to me it comes down to the choice of terrain, steep narrow couloirs, or long tours in more open terrain.

    A couple of other skis in the fun but in the smidge heavier category are the G3 Zen Oxide and the 2011 Kastle FX 94.

    Saturday I did a long approach on my 188 DPS 105s, and Sunday a long steep couloir (crushed a sidewall on a Manaslu in the same couloir last month, found a replacement) plus a short but steep ascent and moderate open descent on the FX 94s, the most enegetic AT ski I have skied.

    Different skis for different terrain

  26. gonzoskijohnny March 31st, 2010 12:40 pm

    Jonathon, your DIN comment :
    “anyone of that weight can stay in any binding (alpine downhill or AT) at those settings”
    is confusing- my DIN 5.5-6 is straight out the chart for 300mm boot (megaride) at my 160 lbs and age (>50) and medium to aggressive level (2-3). I’m also not a weakling, as an ex-bike racer still squatting 350+lbs. But then again I DO NOT straight line coliours at 40+ MPH, and like making lots of turns.
    Kudos to Lou on tinkering with the Dynafits to help us all out, but i gotta think some of you guys must be ex-racers carving on salted snow in stiff downhill boots and stiff Atomics to need DIN 10+ to stay in!
    Maybe i’m really smooth or something (doubtful), but resort skiing double Ds and bumps in Colorado, and 50 days of moderate to steep BC pow (with the occasional minor air and cornice drop) never gives me release problems with Dynafit at 5.5-6. I do work hard at staying centered and skiing with subtle forward and edge pressure to get the skiis to turn for me (178 Manaslu in Pow and 170 Baron in spring mtnring). Only major goof-ups (bouncing out of the bumps, tip breaking through a really hard crust) will force a release. Maybe 2 or 3 times a 60+ day season.
    I do have problems falling out the the Dynafit stock toes pieces when tour mode breaking trail in deep snow, but ONLY if i fail to lock the toe FULLY, usually on step 2 or 3….
    From what I see (and all my ski buds), the stock dynafit (well maintained) set up is pretty dang solid for 99% of good skiers with nil pre-release issues, only blowing out on truly major wrecks. But isn’t that how a releaseable binding is SUPPOSED to work?

  27. Jonathan Shefftz March 31st, 2010 12:48 pm

    Well, I suppose this is getting more into the arbitrary sharp cut-offs in the chart, but seven seasons from now, when I turn from 49 to 50, have no intention of turning back my release settings if my skiing style is still the same.
    Furthermore, I have a hard time imagining any guy coping with variable backcountry terrain and conditions yet staying in at anything less than skier type 2 settings. So that would put a 160 lb 300mm bsl at a min of 6.5 — if you’re able to stay in at less then that, great, but still surprising.

  28. Tony April 1st, 2010 6:56 pm

    Jonathan thanks for the response. Your friends’ situation highlights my question : granted, many boots’ bsl will not let them work with a speed binding and manaslu inserts. Drilling outside the inserts to make them fit would reasonably affect warranty. BUT, when you’re one of the lucky ones and everything lines up just so, why would mounting your speeds then void your warranty?

    Is there something else to it aside from a desire to discourage people from thinking that if they buy a speed it will always work on a manaslu, no matter what your boot size?

    Surely there are better ways to do this than to punish people like your friends that happen to be able to get a useful mount with their boots, the speed & manaslu inserts.

  29. Robie April 1st, 2010 10:24 pm

    Nice fiddling Lou ,
    I’m of the opinion that shim washers would increase pressure but not wear on boot holes because of the fixed stop. Of course as noted a better solution is stronger compression springs.
    One last item (perhaps a old one) for anyone with these older toe pieces a upgrade to TLT speed touring locks (about $24) with the molded in stop prevents touring lock over rotation. And boy trying to peen that pin is a devil ! the hardest part is figuring a way of holding the the toe piece frame.

  30. Hallvard January 27th, 2011 3:38 am

    I ‘m wondering if there exists a totally different way of designing the toe piece to prevent the roll out release. With the short distance needed to get the tech pins out of the holes there is very little elasticity in this release function. And hard to dial in the right release setting.

    Don’t know how to best explain this, but I was thinking if it’s possible (and smart) to make a toe unit where the pins are always closed and that the release function is an extra part holding and moving both pins. This could be something holding the plate with the screw holes. For alpine bindings, when sideways pressure make the boot move it is still held vertically so it’s easier to design some elasticity in the toe.

    What do you think?

    And please don’t patent the solution, don’t want another 20years of relying on only one company… 😉

  31. Christian January 27th, 2011 4:20 am

    As a kid I had a plate binding, where the release mechanism was in the plate, and the boot was fixed to the plate. I had this because it gave a true 360 release, but I am sure it had its share of problems too.

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