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

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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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I am not sure you are correct here.

Ramp angle, binding delta, and forward forward lean certainly have some effectual overlap, but do different things.

For example, increasing delta will rotate the tibia forward but will NOT change the angle created by the foot and tibia. Whereas, decreasing ramp angle (boot board) will rotate the tibia forward, AND WILL decrease the angle created by the foot and tibia. This is important for achilles tendon tension in a neutral stance and the resultant capability to drive a ski. This is only one example of a difference between two of the variables mentioned.

The point being, the three variables do different things.

Fwiw, there are now several threads that discuss ramp, delta, mount point, and forward lean.

I'm interested in hearing more about mount points. Mount point is one variable I am the last sensitive to. Perhaps that is because I have a large amount of dorsiflexion and ankle ROM? Can't remember who stated earlier that increased dorsiflexion could allow for more rearward mount points. Thanks for that! It explains why I've only been bothered by mount points that are too far forward. Great insight.

Whoa... long post, sorry a lot to unpack



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Binding delta and how it is affected by boot sole length is not really much of a factor (not that anybody in this thread is claiming that it is).

14mm delta = .6 degree in difference between a 270 and 340mm bsl
7mm delta = .3 degree in difference between a 270 and 340mm bsl

you could probably get more variation based on what sock you are wearing on any particular day.

I have shimmed my atk and alpinist bindings so that they share the same delta (used skimo numbers as starting point). Having the bindings all set the same and using the same boot makes it easier to go from ski to ski. My lift served skis all use the same binding so again same to same. Different boot lift served and have not tried to find the exact same angle between lift and touring.

@skinipenem, yes, you are right. Cuff angle creating dorsiflexion is not accounted for in that. I should have said:
”my foot doesn’t care if it’s the boot board or binding creating the slope of the base’

What I meant with: “measuring in boot accounts for all variables” was it accounts for both the binding delta and the boot’s own ramp angle. Those difference between tech and resort bindings and boot ramp angles were mentioned before that, and my reply was that this way you don’t have to think about those variables, you just measure the net result.

So I was only talking about the internal boot board angle being the sum of binding ramp and boot construction. Once you have that literal base, you of course still have to consider the effective forward lean of your leg in the boot, created by the cuff angle and how your leg fits in there, and finally, the mount point.

As mentioned above, listed cuff forward lean is not very accurate because of anatomical differences. You could step into your boots and bindings and measure your actual tibia angle that way. But with different boots, the different flexes would create different “dynamic cuff angles” while skiing so I’m not sure how useful that would be.

I’ve chatted with my physio about actual cuff angle in relation to boot board delta ( or cuff angle dorsiflexion as Tjaard says). They say a certain angle is needed to create tension in the achilles. This tension activates muscles and makes the foot/lower leg stronger.

Interesting concept. I find there is something to it. Too open of an angle and I feel looser goosey and weaker. I’d rather have more forward lean and a flat binding delta.

I’ve been skiing Raichle / Kniessel / Full Tilt Flexons for the past 38 years. I’m not aware of published numbers, but they’re widely acknowledged as having amongst the most aggressive forward lean, steepest boot board angle, and deepest forward flex of any currently sold boots. I also ski in STH2 bindings, which again have pretty aggressive delta. Mitigating this somewhat is that I have large-ish (28.5) feet, am tall-ish (6’1”), am lean (175lbs) with very small calves, don’t use any of the optional forward lean shims, have traditional 90’s CSIA ski technique (flexing at the ankle, knee and hip), and have a quiver of directional rear-mounted (Volkl & DPS) skis. I understand this makes me a bit of an outlier given current trends, but it works great for me. I’m constantly trying (I could bore you all senses with my obsession) but find it nigh on impossible to replicate this setup for touring.
It should be possible to formalize all these variables in a system that makes it comprehensible to more than the most experienced and intuitive boot fitters, but I guess most customers are just going to buy whatever the latest star athlete is paid to use.

Throw in tibia/femur length ratio and it gets even more complicated. I have long tibias in relation to my femurs, this puts my center of mass more forward in a flexed ski position. I’m very sensitive to ramp angle whether it’s boot or binding delta. Couple that with high pin sockets on rocker soled touring boots and I need to use pretty tall shims under the toe on tech bindings with higher delta.

I can adjust to boots with more forward lean by moving the boot center 1-2 cm back.


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Originally Posted by ZomblibulaX

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

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Serious question. What is the value-add of Gripwalk?

(1) they force folks to buy new bindings (when it would otherwise not be needed)
(2) they significantly increase the toe height vs a normal alpine binding (ie generally speaking bad on freeride skis)
(3) they feel more vague to skier input (to me) compared to even a replaceable sole boot like the RX or GPX

Is walking around the parking lot that hard? I just don't get it.

as it relates to this thread, they definately reduce one’s ability to fine tune geometry short of jacking up the heel even further.

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Originally Posted by ZomblibulaX

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.



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.

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Does anyone want to make heel shims + screw for CAST?

I currently still switch out the GW shims on new pivots as I don't jive with the 0-1mm delta.

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Originally Posted by Marshal Olson

Serious question. What is the value-add of Gripwalk?

(1) they force folks to buy new bindings (when it would otherwise not be needed)
(2) they significantly increase the toe height vs a normal alpine binding (ie generally speaking bad on freeride skis)
(3) they feel more vague to skier input (to me) compared to even a replaceable sole boot like the RX or GPX

Is walking around the parking lot that hard? I just don't get it.

as it relates to this thread, they definately reduce one’s ability to fine tune geometry short of jacking up the heel even further.

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Looks cool on the shelf, new feature for retail staff to sell Texans.

Attachment 488317

Quote:

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Originally Posted by Marshal Olson

Serious question. What is the value-add of Gripwalk?

(1) they force folks to buy new bindings (when it would otherwise not be needed)
(2) they significantly increase the toe height vs a normal alpine binding (ie generally speaking bad on freeride skis)
(3) they feel more vague to skier input (to me) compared to even a replaceable sole boot like the RX or GPX

Is walking around the parking lot that hard? I just don't get it.

as it relates to this thread, they definately reduce one’s ability to fine tune geometry short of jacking up the heel even further.

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1) a lot of skiing public (people who ski, and are not "skiers") only have 1 ski so its fine

2) that person doesn't care, or have enough experiance to feel the changes, or want to spend the time changing it, or have a boot fitter/nerd to help them

3) Also dont know/care


YES, for "skiers" all this thread makes a differance, but the skiing public (who buys 95% off gear) doesnt

its like your skis, they are FUCKING AMZING, but a 10 day a year skier will usually not be buying them.

Quote:

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Originally Posted by Marshal Olson

Serious question. What is the value-add of Gripwalk?

(1) they force folks to buy new bindings (when it would otherwise not be needed)
(2) they significantly increase the toe height vs a normal alpine binding (ie generally speaking bad on freeride skis)
(3) they feel more vague to skier input (to me) compared to even a replaceable sole boot like the RX or GPX

Is walking around the parking lot that hard? I just don't get it.

as it relates to this thread, they definately reduce one’s ability to fine tune geometry short of jacking up the heel even further.

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If a brand has done GripWalk soles correctly (ISO 23223) and made their binding correctly too, then there is no difference in ramp angle/forward lean between the same boot with ISO 5355 pads and ISO 23223 pads when in a GW binding. On a flat surface, ISO 23223 creates a flatter ramp angle and a more upright feeling stance, but in a GW binding, the geometry of the boot is preserved and is the same as ISO 5355. I've measured boots where there is a 0.25° difference between the two (with GW having more forward lean in the binding actually) but this amount is our allowed production variance anyway, meaning any boot from us can be off by 0.25°.

On the boot side of things, GripWalk allows for a wider toe pad (up to 93mm wide vs. the maximum 71mm of ISO 5355, but most brands seem to be settling around 80-85mm currently), allows for deeper tread patterns for better grip (for sure helpful beyond the parking lot), and the allowance of tech inserts (no brand that ever put tech inserts into a standard alpine soled boot ever got TÜV certifcation for ISO 5355).

If a brand has done it correctly, GripWalk should ski and feel no differently than a 2-component ISO 5355 grip pad.

Nothing quantitative or intelligent about this, but Ive found after a bunch of iterations with different combinations that I personally like three things as a 6’2” male with 33 inseam legs.

1) skis with mount points between -4 to -6
2) binding delta to be between 0-4mm
3) forward lean around 19-20deg - atomic hawx 130 27.5 with 17 deg angle + screwed in spoiler + Velcro spoiler (I’ve been skiing without the Velcro spoiler most of this year, though)

The last is something I know is quite different from most others trends towards upright, but also notice that there seems to be a bundle of pro skiers who do like the same, so I know I I’m not completely crazy, at least. I personally feel most balanced with high forward lean angles, even with forward mounted skis. I notice it especially in steep terrain, and when in the air. Hate higher binding delta, even when adjusting for forward lean. I think this is all mostly due to my body geometry.


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Quote:

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Originally Posted by onenerdykid

when in a GW binding.

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Super helpful details! I'm derailing my own thread, but hopefully you wouldn't mind indulging one quick follow up point and a follow up question.

On the quoted piece, that was my point! I question the value (at least as a univeral change for effectively all skiers) of being forced into a new binding that is 40+% taller in the toe (12-13mm -> 18-20mm), while the heels are mostly all still the same height.

As for the question, the heel pads on GW soles are made from softer rubber, yes? That is what I thought I felt in the mentioned vagueness, but maybe there was just other variables at play, as I certainly trust your expertise and testing, and happy to stand corrected if this is the case!

Cheers man, greatly appreciate your insights and knowledge on this stuff

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Originally Posted by GoldenBC

I’ve chatted with my physio about actual cuff angle in relation to boot board delta ( or cuff angle dorsiflexion as Tjaard says). They say a certain angle is needed to create tension in the achilles. This tension activates muscles and makes the foot/lower leg stronger.

Interesting concept. I find there is something to it. Too open of an angle and I feel looser goosey and weaker. I’d rather have more forward lean and a flat binding delta.

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I have heard the same, for the same reason, from very experienced boot fitters:
If a skier has a high range of dorsiflexion, use a boot(set up) with more forward lean at the cuff (a more closed angle), then compensate for the shift in forward movement of the hips by raising the toes.

Since dorsiflexion is the only body part that I am flexible in, this applies to me too. And like you, I find if my boot is too “open” at the ankle, I can not get good pressure on the front of my foot. Instead, I hit the cuff, and lose the power and control from my foot and ankle muscles.

Quote:

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Originally Posted by MagnificentUnicorn

Throw in tibia/femur length ratio and it gets even more complicated. I have long tibias in relation to my femurs, this puts my center of mass more forward in a flexed ski position. I’m very sensitive to ramp angle whether it’s boot or binding delta. Couple that with high pin sockets on rocker soled touring boots and I need to use pretty tall shims under the toe on tech bindings with higher delta.

I can adjust to boots with more forward lean by moving the boot center 1-2 cm back.


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I have this exact issue. I have a long tibia, and so every mount point feels further forward to me and every boot/binding combo feels higher in angle (more forward) than the average skier. If I have too much forward lean/delta or am mounted too forward, my knees are in an overly flexed position in neutral stance, which is fatiguing and leaves less range of motion to use. Both also make it hard to float in pow, and the tip of the ski gets overloaded in turns. It took me 5-10 years to really figure this out, and my skiing ability/power/enjoyment improved massively over that time. As a result, this is what I do to get a balanced ski position:

-Have upright boots (Atomic Hawx Ultra alpine in the most upright positon, Hawx XTD for touring with the aftermarket chip to get the more upright positon)
-Shim my binding toes. Alpine are zero delta, and tech touring bindings are actually -2mm delta because my touring boots have more forward lean than alpine - even when they are both supposed to be 13 degrees.
-Avoid forward/center mounted skis and/or mount slightly back from the marked line if needed. My favorite skis are mounted between 9 and 13.5cm back from the center of the ski. I've tried several skis mounted more forward than that, and despite really trying to adjust did not enjoy them as much as the more rearward skis.

TLDR: Your body physiology/mechanics/geometry in part determine the ideal boot/binding angle setup, and to some degree, what the ideal ski construction is as well.

Glad people are catching on to the tib:femur ratio and how it affects things. Average ratio of T/F is 0.80±0.03 (according to this study: https://pubmed.ncbi.nlm.nih.gov/26398436/ ) and I'm closer to 0.95, love me an upright boot.

Of course, I have slightly better than average ankle range of motion, thin ankles, wide forefeet, and chunky calves. Optimization of boot fit and performance has been an interesting challenge.

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Originally Posted by mr_pretzel

Does anyone want to make heel shims + screw for CAST?

I currently still switch out the GW shims on new pivots as I don't jive with the 0-1mm delta.

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I’d be in for a couple sets

Thanks for starting this MO. Love this level of ski nerdery.

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Originally Posted by mr_pretzel

Does anyone want to make heel shims + screw for CAST?

I currently still switch out the GW shims on new pivots as I don't jive with the 0-1mm delta.

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I don't have the screws but I could cut a batch of shims, I did it for my touring bindings a bit ago. What thickness(es) do you want?

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Originally Posted by Marshal Olson

Super helpful details! I'm derailing my own thread, but hopefully you wouldn't mind indulging one quick follow up point and a follow up question.

On the quoted piece, that was my point! I question the value (at least as a univeral change for effectively all skiers) of being forced into a new binding that is 40+% taller in the toe (12-13mm -> 18-20mm), while the heels are mostly all still the same height.

As for the question, the heel pads on GW soles are made from softer rubber, yes? That is what I thought I felt in the mentioned vagueness, but maybe there was just other variables at play, as I certainly trust your expertise and testing, and happy to stand corrected if this is the case!

Cheers man, greatly appreciate your insights and knowledge on this stuff

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Alpine Norm ISO 5355
Toe height = 19mm +/- 1mm
Heel height = 30mm +/- 1mm

GW ISO 23223
Toe height (in a binding) = 19mm +/- 0.75mm
Heel height = 30.5mm +2mm/-1mm

Dimension wise, a brand can make the same result between 5355 & GW.

Material wise, a brand can use rubber but they can also use the same materials between 2-component 5355 and GW. If they use the same materials, then they should ski the same.

Quote:

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Originally Posted by onenerdykid

Alpine Norm ISO 5355
Toe height = 19mm +/- 1mm
Heel height = 30mm +/- 1mm

GW ISO 23223
Toe height (in a binding) = 19mm +/- 0.75mm
Heel height = 30.5mm +2mm/-1mm

Dimension wise, a brand can make the same result between 5355 & GW.

Material wise, a brand can use rubber but they can also use the same materials between 2-component 5355 and GW. If they use the same materials, then they should ski the same.

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got it thanks. Your numbers are the thickness of the toe/heel lugs of the boot, not the stack of the binding off the ski (which is what I was referring to), correct?

I don’t think I’ve ever seen a GW binding with less than an 18mm toe stack (to physically fit the bump with space to the ski’s topsheet), where I have piles of 12mm toe stack alpine bindings here.

thanks as always :)

Quote:

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Originally Posted by Marshal Olson

got it thanks. Your numbers are the thickness of the toe/heel lugs of the boot, not the stack of the binding off the ski (which is what I was referring to), correct?

I don’t think I’ve ever seen a GW binding with less than an 18mm toe stack (to physically fit the bump with space to the ski’s topsheet), where I have piles of 12mm toe stack alpine bindings here.

thanks as always :)

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Ah, yes, that was for boot toe/heel dimensions.

For a binding, I am 99% sure that the toe's stack doesn't need to be taller to accommodate the GW bump in the boot sole (it's only 7mm in addition to the toe thickness), but most toe stacks are now taller because most toes are utilizing a sliding AFD, which adds height. If a brand wanted to, they could get the toe lower with a fixed AFD but that idea isn't on many brands' radars.

Couple items:

Shims & screws - Cold River Supply will make you a shim or sell you their universal or blanks in 1,2,3,5,6mm ; Tognar has many / most length screws.

Forward lean: its a hot mess...... I like more than less.

Not mentioned yet, most critical: Cuff Alignment laterally. Biggest issue in past 20 years is that cuffs are getting more strong (out) and we are downsizing more for a precise fit. I have found the static eyeball the shin in the shell useless ( go grab the pitch forks.......). I'm now coaching that cuffs are the boot equivalents to the base bevel. Cuff strong engages at the top of the turn too much and chunders the exit. Cuff soft (in) is vague at the top of the turn and allows butters and slarves and stivots. Too soft, no turn.... Start in the middle & play with it - this has solved hooky skis for myself and softer is better for 100mm skis in freeride mode for me.

Many WCers will run 1.5 on the sole for SL, 0.5 for GS & 0.0 for Speed. YMMV.