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ELI5: Telemark tech underboot gap

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  • ELI5: Telemark tech underboot gap

    Explain it like I'm 5: What is the use of a close (but not too close) gap under the ball of the foot in a tech-toe-based telemark binding?


    I'm referring to a Telemark Tech System setup, but I suppose it might apply to a Telemark Tech Norm setup as well. Obviously, if there's no gap -- or there are parts that push the boot up so high that its heel won't touch down onto the binding heel pad -- that's bad. But I've read in other threads that several millimeters are ideal. But what is the negative consequence of a bigger gap? Or, of essentially none at all?

    I ask because I really like the way these G3 Ion-based TTS bindings ski. They're probably the best-skiing ones I've made, and there's plenty of refinement left to do. There is a 16mm gap between the sole rubber and the binding plastic, or essentially infinite. What am I missing? I can build in a "conventional" 2mm gap or whatever, but what is the reason to?



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    (The F1 Carbon boots I skied them with are on their last legs, as flexi as can be. So the answer is not "The boot sole will sag and get flexed too much when the heel is down." That simply didn't happen -- at least not enough to cause any problems -- and if this binding configuration were to cause that to happen, it definitely would've happened with the worn-out boots I used. And yes, it looks like there's a reverse delta angle going on; I don't know/care what the numbers say, it skied tremendously, so /shrug emoji.)

    **Special shout-out to tele-skier who, despite his stated distaste for cable-based bindings, generously dug out some long G3 cables for me to incorporate. One man's trash is another man's treasure!**

  • #2
    In the simplest analysis, when you drive the ski hard to flex it (bend the ski with your mass) why would you want the chain of force to be driven through the pins, while the boot sole is suspended? It would be better to drive the force through the sole of the boot while it's planted on the ski (or support block) which reduces the force on the pins of the binding. The pins should only control the lateral forces, not the vertical ones... Right??

    Also, with your ball of foot planted on the ski (support block...) you may get a more direct sensation of edging underfoot.

    *You're welcome, as much as I'm not a fan of heel cable bindings, I appreciate all of you creative people taking a crude design and making it into something much more elegant!
    Last edited by tele.skier; 17 January 2020, 08:08 AM.
    the fall line is your friend.... resistance is futile

    Comment


    • #3
      Nice looking binding!

      What tele.skier said makes sense, but if it skiing well, maybe double side tape some cutting boards in there to easily experiment and see if it feels better. Easy to do and to undo.

      It's possible the lack of underfoot support allows the boot to have a rounder flex underfoot.

      Depending on physiology some people have better balance with zero or negative delta. I'm one of them, even 5mm heel high puts me off balance.

      It's hard to know for sure, but I gather many on the World Cup ski zero delta. I saw a picture of Michaela S in a start gate and her binding looked toe high to me.

      Comment


      • #4
        i think maybe you are looking at it the wrong way. the gap is there to ensure that the bellows can drop under weight. if by weighting the ski, it allows the bellows to start compressing, you are less prone to tippy toeing. I don't think the gap can be too big, personally. but doensn't need to be bigger than your weight can droop the bellows.

        think about this like a wedge in other binding, which it seems like all non 2-pin binding use, toe area is higher than ball area of binding. this allows the boot to have some rocker, without cause rocker launch, and that pre curved bellows makes it easier to not go tippy toe. this is just that but better, since you can control it by how you weight the ski at the start of the turn.

        however, having contact at the ball of the foot can lead to a more connected stable sensation, so droop to contact when loaded isn't bad. nor is just unloaded contact. so its preference.

        But with no gap when unloaded, you will also be more prone to ice jacking, both because any build up with jack you, and because you will be able to compress the snow to ice better. and ice jacking bad.

        you need a better heel throw. that just looks wrong.

        Comment


        • #5
          Just looking at the picture, my first thought was instead of freeing your heel, just drop your bellow instead. In biomechanical perspective the result might be the same.

          How do they tour, collapsing over the bellow each step?

          Comment


          • #6
            Originally posted by tele.skier View Post
            why would you want the chain of force to be driven through the pins, while the boot sole is suspended? It would be better to drive the force through the sole of the boot while it's planted on the ski (or support block) which reduces the force on the pins of the binding. The pins should only control the lateral forces, not the vertical ones
            These are some good points. I guess part of it can be chalked up to the crazy unexplainable voodoo power of the tech toe system. The 2 pins don't *look* like they should work, or be durable, but somehow they are -- beyond expectation. Many many Alpine Touring bindings have the boot suspended in the air between the front pins and the rear pins; again, it *looks* crazy, but it works.

            That being said, maybe my setup would work even better with some ball-of-foot contact. Especially for the rear foot. But, is the sole ever really touching anyway once the heel lifts? Or is that just a phantom sensation? As Turnfarmer suggested, I can always attach some material there to see if it makes a difference.

            Thanks for the input, dudes.

            Comment


            • #7
              Originally posted by jasonq View Post
              the gap is there to ensure that the bellows can drop under weight. if by weighting the ski, it allows the bellows to start compressing, you are less prone to tippy toeing. I don't think the gap can be too big, personally. but doensn't need to be bigger than your weight can droop the bellows.
              I agree with all this. I'm very very anti-tippytoe. Whatever can be done to combat it, must be done. That said, I didn't incorporate a large gap by design; it's just a function of the plastic part's minimalist form factor (and the Ions' ridiculous 40mm pin height). After testing, I could always design-in a higher rear platform if it ends up improving the skiing.


              Originally posted by jasonq View Post
              think about this like a wedge in other binding, which it seems like all non 2-pin binding use, toe area is higher than ball area of binding. this allows the boot to have some rocker, without cause rocker launch, and that pre curved bellows makes it easier to not go tippy toe. this is just that but better, since you can control it by how you weight the ski at the start of the turn. however, having contact at the ball of the foot can lead to a more connected stable sensation, so droop to contact when loaded isn't bad. nor is just unloaded contact. so its preference.
              This makes a lot of sense. Perhaps it is simply about personal preference. Though maybe one can sort of get best of both worlds. Perhaps the G3 Ion toes are so stout that they really compensate for the lack of ball-of-foot contact, and I can get that good pre-lift curve while also having good control. Perhaps I'd feel a lot less control if I had used wimpier toepieces.


              Originally posted by jasonq View Post
              you need a better heel throw. that just looks wrong.
              Haha, it does look horrible. It's the stock OMG one. But as horrible as it looks, I don't think I've ever had one pop off unintentionally, and I've probably skied 1000 laps with F1's and those heel throws. I've started in on designing my own, just so I can print them whenever I want, but until then I'll keep rocking the OMG's.
              Last edited by bobbytooslow; 17 January 2020, 06:41 PM.

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              • #8
                Originally posted by iBjorn View Post
                Just looking at the picture, my first thought was instead of freeing your heel, just drop your bellow instead. In biomechanical perspective the result might be the same.
                I think this probably does happen to some extent. As jasonq said, it gets the bellows already flexing before your heel leaves the pad, setting you up to be very not tippy-toed.


                Originally posted by iBjorn View Post
                How do they tour, collapsing over the bellow each step?
                They're certainly not floppy like leather boots. The somewhat-flexed bellows is nothing new for me, as I skin with a low heel riser up for pretty much everything but long flats (boots with big rearward ROM allow this; it's how skimo racers do it). So I get that same sag when touring on all my other TTS rigs too. My feet curve like that when I'm climbing a hill in running shoes, so it feels natural and efficient to me to do it in ski boots. Other folks' biomechanics may vary.

                Comment


                • #9
                  Originally posted by bobbytooslow View Post

                  These are some good points. I guess part of it can be chalked up to the crazy unexplainable voodoo power of the tech toe system. The 2 pins don't *look* like they should work, or be durable, but somehow they are -- beyond expectation. Many many Alpine Touring bindings have the boot suspended in the air between the front pins and the rear pins; again, it *looks* crazy, but it works.
                  Right, but the fixed heel of an AT binding limits the boot's ability to work as a lever on the front pins because the heel doesn't allow the length of the boot to work like a breaker bar on the pins, so there's only point loading on the front pins, not a "boot's length lever" induced multiplication of force...

                  Originally posted by bobbytooslow View Post
                  That being said, maybe my setup would work even better with some ball-of-foot contact. Especially for the rear foot. But, is the sole ever really touching anyway once the heel lifts? Or is that just a phantom sensation? As Turnfarmer suggested, I can always attach some material there to see if it makes a difference.

                  Thanks for the input, dudes.
                  To be honest, I have to play this card again... Technique has a lot to do with what forces you want your binding to generate and why a person prefers a certain "feel" to their binding. I still ski freerides without much spring tension on them. I don't crank my boot over to load pressure into my uphill ski. I stand on it firmly... and the bellows bends from my weight, not from lifting my heel against some heavily sprung heel cable.

                  Bobby, You should ski it that way and see if you like it... I'm interested to hear your impressions.
                  the fall line is your friend.... resistance is futile

                  Comment


                  • #10
                    Sorry Bobby, I was up to waist (and chest) in the white stuff today and didn't see this till now. Could have given you the 5 year old explain:

                    It's most comfortable (after much trial and error) to have about a 2mm gap under the bellow. Now, as you say, your boot may be different than the super soft bellowed TXPro I did all my experimenting with, but that is what I found. Flush with the bottom of the boot and it feels like there is a ball under your foot (uncomfortable), too much gap and the bellows sag too much and toes get crunched (uncomfortable). I also think you get more power to the edges with that spacer there (also trial and error).

                    I really like your binding. Looks super simple. I don't think I'd like being that high off the ski. The Ion toe is about as high as I like. But as you said, you really like the way they ski, so aside from safety/annoyance (that heel throw looks like it might not hold) you shouldn't listen to us!

                    Comment


                    • #11
                      That's very sleek and solves the spring bottom out problem (for some of us, anyway) - right?

                      Why not try a lower heel and tech toe with a lower pin height to compare?

                      Comment


                      • #12
                        Originally posted by dschane View Post
                        That's very sleek and solves the spring bottom out problem (for some of us, anyway) - right?

                        Why not try a lower heel and tech toe with a lower pin height to compare?
                        I don't believe the bottoming-out problem will ever be solved, unless I incorporate that giant spring running across the top of my garage door. These are Meidjo springs. They don't bottom out with my F1 Carbons, but as I've written as nauseum, their flexi boot soles make even Voile X2 springs not bottom out. We'll see what happens with big-boy boots.

                        So the reason I used the Ion toe is because it has a 40mm wide mounting pattern, necessary to fit 2 springs in between. Dynafit and most others are 30mm wide. The only others at 40mm are the Atomic Backland/Salomon MTN bindings, but no one sells just the toes.They have a 30mm pin height as well, so yeah they'd be my preference. If anyone wants to split a set, let me know!

                        Why not just use one spring, Pitbull-style? Stay tuned...

                        Comment


                        • #13
                          The other aspect that I forgot to mention is boot delta. I had an issue with the rottefella freedom binding's boot delta (low heel) Basically the combination of boot delta and boot's cuff lock angle give you a resulting fixed "shin angle" when your heels are both down. This determines where your center of mass is in relation to your feet. In my case, It put me in the back seat, so I just added a shim under the heel block since there was no option of a "riser" to mill down to lower the binding's toe piece. That taller heel worked for me, and allowed me to keep the more efficient, tall, well centered stance that I prefer.

                          If your cuffs are unlocked, then you can lean forward to adjust your center of mass to be properly over your feet. People who ski with unlocked cuffs do this automatically to be well centered. The only issue boot delta has on them is whether or not they are comfortable skiing with the angle their foot is flexed at to compensate for the boot delta.

                          If your boot's cuff lock is nearly vertical and your boot delta has a low heel, then your center mass can be too far rearward with both heels down. The effect of this is that it takes longer to get tip pressure to your skis because you have to overcome your rearward position by bending your knee and lifting one, or both, heel/s. There are alpine skiers who ski like this. I've heard them referred to as "tail gunners" because they actually lean back on their boots and steer from the back seat... I don't think I've ever seen a tele skier do that.

                          If you lock your cuff lock in the forward position to compensate for the low heel boot delta, then you ski with a more flexed knee and your resting position is with a more flexed knee, which is muscularly less efficient than adjusting the combination of boot cuff lock angle and boot delta to give you a well centered postion at near full knee extension simultaneously. So dialing in these variables becomes a way to be muscularly efficient and save energy at full extension.

                          I always post this image as a visual aid to make my comment easier to understand...

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                          Last edited by tele.skier; 18 January 2020, 08:14 AM.
                          the fall line is your friend.... resistance is futile

                          Comment


                          • #14
                            Very nice looking binding BTS! You even have a color correct front riser, impressive.

                            Regarding the gap under the ball of foot; I experimented with this and concur with Jim and Jason (to some extent) that you need a gap for the bellows to droop. But I also feel that you need that platform for the ball of foot at the boot sole to be supported. Think of it as a fulcrum with the boot pivoting underfoot (if you’re geometry is good)against the cables and the pins holding the boot toe in the vertical plane. If you have excessive gap here the connection becomes vague with no grounding of the sole on the ski. I personally want to feel the ball of my foot on the ski as my skiing is very upright and rear ski biased in turn initiation. Two years ago I added a 1/8” shin under the mid block on my main TTS binding time close the gap to around 2mm. The shim also allows me to vary that pivot height by wher I position the shim.
                            Last edited by Allan Fici; 18 January 2020, 08:25 AM.
                            Function in disaster, finish in style.

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                            • #15
                              I agree with teleskier on the biomechanics regarding the boot/ binding interface in relation to your own natural posture. You also have to consider the boots geometry in regards to drop from heel to ball of foot. They’re not all the same and if you customize your boot fit with insoles, footbeds, shims and such you can have a big effect on the drop. As an example with the way that I fit my own boots, I then strive for a more neutral ramp angle on my bindings. This just works well for me and gives me a better connection to the ski.
                              Function in disaster, finish in style.

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