NERDING OUT- Mount Position, Cuff Angle, Binding Delta, and the like

This conversation has sprung up in conversations in buried in other threads, and based on folks posting, thought it deserved its own. Maybe it already exists, and if so, happy to move these thoughts to the right place. Mainly, just wanted to share the results of my own experimentations over the years and hear what other folks are experiencing too, as it really helps get folks mounted mounted in the right place the first time you drill a pair of skis.

None of these thoughts are intended to be presented "right" or dogma, just some observations. Hopefully folks with REAL biomechaincal insights can correct any of my purely anecdotal observations with real facts - I know on the race side, there is alot of hard science here that I am not across. Ideally others can share their experiences too.

A little background
- grew up skiing 20*+ forward lean boots from as long as I can remember, going back to the orange Tecnica TNT boots. More often than not with spoilers in the cuff to take up space and jack the boots forward more
- Started skiing "more modern" lean angle boots about 12 years ago with the Tecnica R9.8 (I believe it was still 16* cuff angle, with a 2.5* spoiler).
- Switched to Dobermann 98mm last and ~14* cuff angle, still with a 2.5* spoiler 3-4 years ago and pulled the spoiler mid season this year. It was a noticeable performance gain for my far less athletic mid 40's dad-bod self compared to a setup my far more fit early 30's self could easily ski hard all day with.
- Have some 12.5* boots enroute to experiment with.

How ski shape relates to mount
- Firstly, fore-aft balance is really important, and obviously imbalance gets exacerbated in variable/punchy/grabby snow.
- For hardpack-based skis, I like to generally be mounted near the center of the sidecut to balance the turnshape on firm snow, but interesting behaviour does existing when you are not super close to the ski's waist.
- Pintails (ie sidecut much further back than the mount) really like to carve DOWN the fall lineopposed to coming accross the fall line. For those on the FL113, this is where that behaviour comes from (the mount is ~12cm in front of the center of sidecut), so it is important to use the correct amount of taper and large turn radii to match the ski's behaviour.
- I find <5cm variance of mount to ski waist to be subtle on snow for skis with a decent amount of taper/rocker. For more conventionally shaped skis with less taper, the smaller the sweet spot since the tips/tails hook up more aggressively.

How my mount positions started to evolve.
- OG skis paired with 20*+ boots generally corresponded to -15 to -17 mounts (!!!) and even "progressive" skis the the 1st gen Gotamas had -13cm lines.
- About 10-12 years ago, coinciding with the R9.8 boots and probably my first <20* boots, my preferred mounts all of a sudden became came to the -10.5 to -12.5 to maintain balance in punchy snow.
- Most recently, with the move to the 14* (no spoiler) setup, I am all of a sudden moving mount points (that I know and loved) 1 to 1.5cm forward.

Observations from playing with it this season so far
- Been skiing with and without spoiler in my cuff and various demo bindings with different deltas this season
- I loosely correlate ~2-3* cuff angle change to ~1cm to 1.5cm of mount correction to maintain balance
- I find ~5mm binding delta changes to feel similar to a ~5mm of mount correction - ie higher toe effectively reduces your cuff angle and a lower toe effectively increases your cuff angle.

A Few Early Conclusions
- its alot easier to add spoilers than make a boot more upright
- I hate skiing in demo bindings, haha
- I am really digging more neutral boots and incrementally more forward mounts than I ever could have imagined, but at least for me, they needed to go hand in hand.
- Binding delta may not be obvious, and plenty of folks are nervous to pull toes and remount, but if you feel like you missed your ideal mount point by a little bit too far forward, adding a 5mm shim could help. Shims/screws are available at many shops for many toes.

Very curious if others have noticed and experimented with this is any meaningful way in a freeride setting.

**Note - there is not a real defined WAY to measure cuff angle, since it is a complex shape, not a straight cylinder. Therefore, finding cuff angles can be hard and the numbers out there are approximations. So everything mentioned above carries the "YMMV" and all of that.

nice info, and good to see it all written down

other points:

boot ramp angle can also effect this, AND changes based on size. IE: a 22 boot has a steeper angle then a 29 boot. The toe and heel are the same height and differance, but this is spread over a shorter lenght of foot so more angle in smaller boots


A boots F lean might be the same, but a person with a bigger calf will be more forward in that same boot then someone with chicken legs as less calf to be pushed forward


A person with a greater ankle range of motion, can often use a further back mounting point, as they can flex farther, so move their own balance point a greater range from upright/neutral to the max forward possition.


Binding ramp angle is also anoher variable that plays into the skis mounting point. (I've skied the same ski, but changed the ramp angle and it skied VERY differently)

Hugely important topic but IMO it's hard to get past subtleties of anatomy to discuss hard numbers.

My little mantra for the past few years when pondering these things:

"How does factor x affect where my center of gravity is projected onto the ski?"

Great post, Marshal !

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Originally Posted by mntlion

Binding ramp angle is also anoher variable that plays into the skis mounting point. (I've skied the same ski, but changed the ramp angle and it skied VERY differently)

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This is my current dilemma, I'm used to the STH2 WTR which has a delta of 5mm, and considering a CAST setup but the delta is 0mm and I'm pretty sensitive to that, though choice !

Btw I've always wondered what's the equivalence between alpine binding deltas and touring binding deltas.
I guess it depends of the boots you're using.
For me it feels like a 5mm alpine delta is more or less equivalent to a 12mm touring delta, something like that.
It would not be very complicated to measure I guess.

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Originally Posted by stuntmanbo

Great post, Marshal !


This is my current dilemma, I'm used to the STH2 WTR which has a delta of 5mm, and considering a CAST setup but the delta is 0mm and I'm pretty sensitive to that, though choice !

Btw I've always wondered what's the equivalence between alpine binding deltas and touring binding deltas.
I guess it depends of the boots you're using.
For me it feels like a 5mm alpine delta is more or less equivalent to a 12mm touring delta, something like that.
It would not be very complicated to measure I guess.

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If you go cast, and want more binding ramp, odds are a more racey shop can add some WC shims under the heel and find longer screws?

I’m starting to notice I’m having issues with my cuff being slightly off left to right. Not 100% sure which leg but it got exasperated when I switched from rossignols to k2. For sure in need of a cuff alignment atm.

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Originally Posted by Norseman

Hugely important topic but IMO it's hard to get past subtleties of anatomy to discuss hard numbers.

My little mantra for the past few years when pondering these things:

"How does factor x affect where my center of gravity is projected onto the ski?"

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awesome mindset to have when trying to trouble shoot! Great point!

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Originally Posted by mntlion

nice info, and good to see it all written down

other points:

boot ramp angle can also effect this, AND changes based on size. IE: a 22 boot has a steeper angle then a 29 boot. The toe and heel are the same height and differance, but this is spread over a shorter lenght of foot so more angle in smaller boots


A boots F lean might be the same, but a person with a bigger calf will be more forward in that same boot then someone with chicken legs as less calf to be pushed forward


A person with a greater ankle range of motion, can often use a further back mounting point, as they can flex farther, so move their own balance point a greater range from upright/neutral to the max forward possition.


Binding ramp angle is also anoher variable that plays into the skis mounting point. (I've skied the same ski, but changed the ramp angle and it skied VERY differently)

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Awesome points, thanks D!
I don't have experience on the variance between different people, so helpful indeed.

Do you generally see it as "if you have a small foot and feel too far forward, consider griding your boot board flatter" or "If you have voluminous mid-leg / lower calf attatchement, and feel too forward let's try on a more upright boot"?

Obviously lots of relative points here, and you can't fit on the internet, so I am mainly curious what the "rubber meets the road" indicators might be, to help folks better verbalize to boot fitters when they need help in this stuff.

Cheers man!

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Originally Posted by mntlion

If you go cast, and want more binding ramp, odds are a more racey shop can add some WC shims under the heel and find longer screws?

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Another option could be to try the STH with a 5mm toe shim just to see how that changes things before drilling with Cast.

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Originally Posted by mntlion

If you go cast, and want more binding ramp, odds are a more racey shop can add some WC shims under the heel and find longer screws?

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Good idea, but would that work with the brake retainer though ?

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Originally Posted by stuntmanbo

For me it feels like a 5mm alpine delta is more or less equivalent to a 12mm touring delta, something like that.
It would not be very complicated to measure I guess.

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This may be true with the same boot in both bindings, but important to note that some/many touring boots have higher heels (ie more boot board ramp angle) internally than alpine boots, so I personally can't ski more than 5-6mm pin delta with my touring boots without feeling like I am constantly falling forward. Point being, get the right boot, then build the system around it!

So the 30k foot view here would be that the more center mounted your ski, the more upright your stance should be? Just feels so much less athletic to me. And if I went from a Katana to a Deathwish, would almost necessitate different boots?

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Originally Posted by stuntmanbo

Good idea, but would that work with the brake retainer though ?

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no idea. Ask the cast folks

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Originally Posted by Marshal Olson

Awesome points, thanks D!
I don't have experience on the variance between different people, so helpful indeed.

Do you generally see it as "if you have a small foot and feel too far forward, consider griding your boot board flatter" or "If you have voluminous mid-leg / lower calf attatchement, and feel too forward let's try on a more upright boot"?

Obviously lots of relative points here, and you can't fit on the internet, so I am mainly curious what the "rubber meets the road" indicators might be, to help folks better verbalize to boot fitters when they need help in this stuff.

Cheers man!

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more if you feel this (regardless of foot size, calf size,etc) then do this. The calf size might be WHY you are feeling too far forward, but the calf can't be changed, just a cause. So still need to change other things

Good discussion. I’d love to get more hard numbers and ways to predict these things accurately. I feel like Lou would have some of those answers.

What it seems like to me (from Marshall’s discussions before) is you always want your weight going through the same spot on a ski:
- Forward lean boots with traditional skier puts a weight bias forward so mount needs to be rearward.
- Upright boots with upright skier needs mount further forward to get weight in the same location as above.

For big calves and increased forward lean: in extreme cases I change the e forward lean in the boots. Make them more upright and get that tibia where it would be in a regular legged person. Big calf people also suffer from the boots feeling soft for two reasons, one, the boot is wide open and less stiff and two, they are leaning on their shins with a 20 degree lean. Preload is huge and it’s easy to flex further. In the recent blister deep dive on boots, Bryn had this wrong. Big calves DO push you further forward because the leg is bigger inside the boot. Forward lean is supposed to be a measurement of the tibia angle but our boots are rigid on the back and the tibia is forced forward (and buckles loosen) when volume is too high.

To add to this, the more upright a boot is, the softer it can be. It’s harder to flex a boot forward when it’s upright.


I have small feet and like forward lean but hate ramp angle. I shim most my touring toes. For a while I thought I wanted a more upright boot, but it was the ramp. Changing the ramp gave me my balance back and made my skis less twitchy in the tip.

We need a better list of binding deltas that cross compares alpine and touring. In my mind, the top of the toe and heel lugs should be there reference point to measure off.

There's another part of this which is about resultant position. Like Djongo likes to say, a great skier can ski any equipment and make it work. I think that's true. But each ski wants to be skied from a certain point. As the equipment changes mount point, boot angle, ramp, etc, you have to change your body position to get yourself in the ski's pocket.

I can use different boots on the same ski, or change the mount point a little, and still get the ski to act like I want it to, but it often requires me to move my body around. It requires some weird gymnastics when the mount point is off, cause you can no longer weight your foot the right way (either more pressure on toes or heels than you'd normally want to have) but it's not that bad to deal with different boot angles.

So sometimes this is about finding gear that puts you in the body position you want. I'm in S/Max 130s (13.5 published angle). I found that if I use shorter poles than the old days it encourages me to bend my knees more and lower my body, which I like. As you do that your upper body needs to straighten to keep your weight centered where the ski wants it. And it changes per ski - pretty darn straight upper body for ON3P jeffs, which want to be surfed and are pretty centermounted, and not very straight on Line Supernaturals, which have a more trad mount and want weight a lot more pressure on the shins.

Anyway, I like to think about these angles and mount points not as dictating how the ski is skied, but rather in terms of how they allow my body to position itself when I'm skiing the ski correctly. I like to think I could probably ski most any setup pretty decently, but one that matches how I like to be positioned is just way more comfortable and fun.

^ Yep, exactly. Good post.

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Originally Posted by Marshal Olson

This may be true with the same boot in both bindings, but important to note that some/many touring boots have higher heels (ie more boot board ramp angle) internally than alpine boots, so I personally can't ski more than 5-6mm pin delta with my touring boots without feeling like I am constantly falling forward. Point being, get the right boot, then build the system around it!

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Too deal with the difference between (my) touring boots and (my) resort boots, I just measure the boot board ramp angle inside the boot, with the boot clicked into the binding.
This way it takes into account all the variables, boot and binding. After all, my leg doesn’t care if it’s the boot or the binding that is creating the ramp angle.

I started this thread a while back that hit on some of this, but maybe not all of it...

https://r.tapatalk.com/shareLink/top...ink_source=app

Geeking out on ramp angle/delta.

My initial hunch that started the thread is that less binding delta is better suited to more forward mounts, but you are expanding on that here.

Sent from my SM-A536W using Tapatalk

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Originally Posted by Tjaardbreeuwer

Too deal with the difference between (my) touring boots and (my) resort boots, I just measure the boot board ramp angle inside the boot, with the boot clicked into the binding.
This way it takes into account all the variables, boot and binding. After all, my leg doesn’t care if it’s the boot or the binding that is creating the ramp angle.

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How do you measure it?

Like I had my iPhone in there and a mirror haha.

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Originally Posted by CaliBrit

How do you measure it?

Like I had my iPhone in there and a mirror haha.

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Hah! I'd do it with a square measuring off the vertical end sticking out of the cuff. Iphone could still do the measuring if needed

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Originally Posted by strange meadow lark

Hah! I'd do it with a square measuring off the vertical end sticking out of the cuff. Iphone could still do the measuring if needed

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Much more intelligent.

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Originally Posted by strange meadow lark

Hah! I'd do it with a square measuring off the vertical end sticking out of the cuff. Iphone could still do the measuring if needed

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Yep. That’s what I do. L square in the boot, measure off the vertical arm. I have a dedicated clinometer, because I don’t like pulling my phone out of its hardcase all the time, but the phone apps work fine.

Just make sure the skis are on a full length surface. At first I just put the skis on my 2 tuning supports, forgetting that different rocker might affect the angle.

Quote:

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Originally Posted by stuntmanbo

Btw I've always wondered what's the equivalence between alpine binding deltas and touring binding deltas.
I guess it depends of the boots you're using.
For me it feels like a 5mm alpine delta is more or less equivalent to a 12mm touring delta, something like that.
It would not be very complicated to measure I guess.

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YES. I've struggling massively to wrap my head around this. Ski Lange RX 130s (12 degrees) and Pivots (5mm delta?) and they're great - feel little too upright (but mostly great) on trad-mounted Volkls and perfect on -4.5 or -5.6 mounted K2s. Going between the two takes half a run of adjustment. ZGTPs (also 12 degrees) with shimmed-toe ATK/Hagan Core 12 Pros (8mm) feel wickedly upright and horrid on moderate and progressive mounts (-9 to -5). This was very surprising - if the lange/look combo rules, why does the balance of ZGTP+ATK+toe shim feel so stupidly backseat? Ditched the toe shims on the ATKs and things are better. ZGTP + unshimmed Dynafit Vertical STs (~16mm delta) was a bit too much, however ... despite Vulcans/TLT6s (both 16 degrees) being largely fine in those Dynafits for almost a decade. I give up.

I've actually reduced and made my quiver more consistent over this - having to "figure out" new balance points on touring rigs in particular is just not worth it as you don't get the repetition.

Quote:

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Originally Posted by mntlion

A person with a greater ankle range of motion, can often use a further back mounting point, as they can flex farther, so move their own balance point a greater range from upright/neutral to the max forward position.

Binding ramp angle is also anoher variable that plays into the skis mounting point. (I've skied the same ski, but changed the ramp angle and it skied VERY differently)

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1) Yup. Static fwd lean measurements are useful for a baseline, but the "rubber meets the road" Marshal mentioned is the angle of the tibia when the skier engages the ski, and like EWG said, where your center of gravity is in relation to the center of the sidecut. Dorsiflexion/ROM, boot stiffness, length of levers are constant variables that keep this from being an exact science, not to mention BSL, skier weight and just flat out effort.

2) Anyone that went from a pivot alpine AFD to the gripwalk AFD can immediately attest to this.

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Originally Posted by stuntmanbo

Good idea, but would that work with the brake retainer though ?

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Brake retainer will still work with <3mm shim, but safer to just cut a shim for the heel and the brake retainer/elevator out of a single sheet of ABS.