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Uncle-A

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@SkiDuzzi are you more confused now than at the beginning of this thread? One more thing is with a lot of talking about the binding position on the ski, what is your BSL because moving the mount forward will feed different to a size 9 compared to a size 12. I have the opinion that the larger boot sizes do better with the forward mount and the average size boot sizes (10 or less) do better on the manufacturers mark especially on the narrow waist skis like the AX. If you do decide to ski with a forward mount the 182 is still my recommend length.
 

martyg

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Length hasn't changed that much.
Ligety went from 191cm/29m to 195cm/35m. Now they're back to 193cm/30m.
It's hard to make absolute conclusions as course sets can change also.

I think in '98 Olympics they were using 198cm, and carving a lot. Sort of shaped. For the period. After that I'm not sure what happened. People might have gone a little nuts with shape and length. Like in slalom. 2003/4 gs got the 185cm/21m rule. 2007/8 27m and 65mm min width. Not sure on length.

http://www.tedligety.com/opinion/


I was specifically referring to what was going on with committees and in the board room regarding ski length specs.
 

ScottB

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@SkiDuzzi are you more confused now than at the beginning of this thread? One more thing is with a lot of talking about the binding position on the ski, what is your BSL because moving the mount forward will feed different to a size 9 compared to a size 12. I have the opinion that the larger boot sizes do better with the forward mount and the average size boot sizes (10 or less) do better on the manufacturers mark especially on the narrow waist skis like the AX. If you do decide to ski with a forward mount the 182 is still my recommend length.

There seems to be a lot of variation on where to mount the binding on the 183 AX. Some amount of forward shift seems to be preferred.

Speaking as a person with larger boots (29.5) I always mount my binding further back from the line. Physics dictates this and its not an opinion. Not all skis need this, and there is personal preference involved as well.

The mark on the boot is always at the middle of the boot sole length. So as your boot gets longer, your toes will be more forward on the ski if you mount on the line. In theory, a skis wants the pressure to be applied at the same point regardless of the force. To keep your toes in the same spot for different size boots, larger boots move back and smaller boots move forward from the midsole mark on line of ski. The typical reference boot length where the mark on the ski is in the right place is 27.5 for a mens ski.

A lot of women with small feet, especially on mens skis, can struggle with their center of pressure (called "ball of foot") being too far back on a ski and they should have their binding mounted more forward.
 

Uncle-A

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@ScottB what law of physics are you referring to when you say that it "dictates it"? My opinion on mounting forward is not only mine, many people who have mounted binding do the same. The first thing that comes to mind is that when a mount is done by placing the toe of the boot at mid cord length of the ski. Some still mount using that method disregarding the center of boot sole or if a manufacturers mark can't be found. That is when a bigger boot should be moved forward.
 

ScottB

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By laws of physics I mean a force balance or analysis of the forces. As far as I know what I am about to say holds true for all skis, although rockered skis are different than fully cambered skis in terms of mount position.

Anyway, for a fully cambered ski, the mounting technique is to identify the contact points, find the center between them, called center of running surface, and then put the ball of foot center on the center of pressure. This is where the skiers weight force should be applied to the ski. As you shift your weight from your toes to your heels, the center of pressure shifts a little, but when you are pressing on your boot tongues, your center of foot pressure should be on the pad of your foot just aft of your toes. I don't know what its technically called.

Lots of fancy words to say the mark on the boot is always at the center of the boot. When the mark of the ski is chosen, its for a certain size boot, intentionally or not. If you put the middle of the boot on the mark, different size boots move the ball of foot position on the ski. Therefore the center of pressure shifts with foot size. In theory, the center of pressure should be at the same location on the ski. If you are still following me, this means you mount at a different position for each size boot. The factory mark to boot sole mid mark is really right for only one size boot, the "reference" size boot that was used to determine the factory mark. Larger feet will have to be moved back to keep the center of pressure at the same place on the ski.

In reality, most skis are not that sensitive to mount position, so one spot works as a good "averaged" position. This is how the whole "ski mark" and boot mark mount position works.
 

ski otter 2

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That is really interesting about the bindings feeling different. Maybe its the height? I need to mount up a 183cm Laser AX and I have a Tyrolia PRD 12 binding and need a plate or dual plate (I assume you have the dual plate) and I have a non AT Tyrolia Attack2-13 demo binding. I was leaning towards the PRD 12 with a one piece plate. Which would you recommend and why?

Tough question. Your two choices would actually reverse the heights of the two set ups I've tried, I think. So I'm not sure.

Probably the PRD with race plate (I know I'd love that), but .......

It's hard for me to say, actually, which I'd choose, of the two I've tried, let alone your two. Pluses and minuses to each, all excellent, more than likely. (That ski is so good.)

The way a long time top Head rep described the difference to me, an all mountain binding like the Attack2-13 has more play in the toe than a race binding or the PRD, and this makes the ski feel more playful, less single-tracked or directional, if you will, as that Attack toe gives a bit either way without the skier being aware of movement, for the most part. (The rep was actually flexing that toe on a Head Kore 93 as he spoke, showing me the extra play.) I liked that extra playfulness.

At the same time, the extra height of the AT version of that Attack binding gave it an extra race binding-like authority over the edges - just control and turn on a dime feel, without loosing the playfulness of the Attack2-13 toe. I liked that extra height/leverage/authority.

If I had to choose, I'd go for the height over the playfulness, but then, I don't ski bumps for hours.

So of your two choices, I'd say it partly might depend on how you want to use the ski: do you want it to feel like a versatile race ski, and charge it with command and smoothness (and only in bumps here and there each run) or do you want it to get playful in off piste bumps a lot?

If fewer bumps, I'd choose the PRD 12 with the extra plate height, over the lower, standard Attack2-13, probably, but not sure unless I tried it: I never demoed that lower Attack2-13 on the AX, and might like it, dunno. I'd guess the higher and more directional PRD w. plate will feel extra smooth and in a directional groove, with the authority/extra leverage of that plate. More like a race ski, commanding the edge, while still being a frontside biased all mountain ski, to me.


I'll have to check out my pair to see if I have a dual plate. I think I don't, that mine is flat on the ski. (I wanted more contrast to a race ski feel, one way or another: I already have plenty of FIS race skis (sl & gs) with Free Flex plates, etc., and cheater race skis with plate, and wanted a pleasant change up and contrast to that, and the bit of extra versatility (in some bumps and crud every day).

For the same reason, I got a pair of Head World Cup Rebel iSpeed 180/18, instead of the similar spec ski in the iSpeed Pro (with full on race plate). That 180/18 ski I was on today, last day at Mary Jane, and I was skiing it in bumps quite a bit. It did just fine. Two days ago, I was also at Mary Jane, on the AXes - just fine too.

My friend wishes he'd gotten a plate binding instead of the Attack2-13 ATs, wanting a more race ski feel at speed. But my first choice would have been his setup over mine, ambivalently, by a hair; though he likes both our setups. Go figure.
(If I didn't already have the race skis, I might well have agreed with him. The PRD 12s work very well. Man, what a neat ski.
 
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James

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Since ScottB put a 0.5 on the ski, it doesn't seem like he'd want that play of the Aatack 13.
 

Noodler

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That is really interesting about the bindings feeling different. Maybe its the height? I need to mount up a 183cm Laser AX and I have a Tyrolia PRD 12 binding and need a plate or dual plate (I assume you have the dual plate) and I have a non AT Tyrolia Attack2-13 demo binding. I was leaning towards the PRD 12 with a one piece plate. Which would you recommend and why?

Can I pick "none of the above"? ;)

If I had to pick one of the available options it would be a tough choice. Personally I prefer the flatter delta of the Attack, but you can use the Twin PR Base for the PRD bindings which will allow you to shim the toe if necessary. I don't know if you've experimented with binding delta, but my eyes are forever opened after my testing this past season. It really is a critical factor in getting your fore/aft stance alignment dialed-in.
 

ScottB

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So I took some measurements of my Attack13 demo's and my PRD 12's. The PRD's have a stand height of around 34 mm and the toe and heel are within 1mm of the same height. The Attack's are 24 mm heel and 21 mm toe. They have a binding delta of 3 mm. I prefer zero delta, so the PRD's are the better option for me.

I think I know why the PRD's have to move more forward. The Attacks have no plate so the toe weight (force) goes directly to the ski under the AFD. For the PRD's, the toe force goes into the AFD, then into the "plate" then into the ski. The plate will spread the force out a little, with the effect being to move the "center of force" more rearward. Hence you have to slide the binding more forward to get the same "center of force" to the ski.

Time to get out of my physics comfy chair.

I looked up the heights of the bindings:

Attack AT 24/21 Heel/toe
Attack GW 17/14
PRD 12 GW 33.5/33.5

This might be older info, not sure about current binding numbers
 
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ski otter 2

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@ScottB, hi again.

I read with interest your above posts about mount point, etc. They make some sense. But I'm not sure where this fits in overall, since it seems to run counter to what I've experienced, and what I'd use myself.

I think of mount points, and arrive at mount points, very differently than your above process, both more intuitive and experiential.

To partly generalize with you as an example, because you are bigger (taller, stronger, heavier, more leverage, center mass farther from the ground, etc.), you are likely to need either a longer ski, or a ski mounted farther back for stability, float and handling/carve dynamics - no mention of boot size, but maybe that's another factor.

(I know most brands test binding deltas with a specific boot length, an average-sized one: usually 26.5 or 27.5. I'm 26.5, average; but I would not use this to determine mount point. Maybe I should, as one option? :rolleyes:)

I recognized what you wrote as a common way some folk have found mount point, going way back. And I've heard that for many this works.
Maybe many brands use a version of this (to at least use contact length and center of contact length as a reference).

But don't skis these days have mount points dependent on their overall design, use and the style of their intended skiers - and prototyping - not just contact length and boot length? Many skis, for example, have traditional mount points, freeride mount points, and freestyle or trick mount points for the same ski. No mention of boot sizes. Freestyle skis tend to have mount points closer to center, for tricking. Freeride skis tend to have mount points farther back, in between that and race or traditional mount points. For finding the right mount point, lots of mention of relative ski performance, bigger or smaller guys, freeride or freestyle; then testing, and adjusting, based on what skis best.

I'm just a bit confused. What I'm saying must be well known to you too.
 

Noodler

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So I took some measurements of my Attack13 demo's and my PRD 12's. The PRD's have a stand height of around 34 mm and the toe and heel are within 1mm of the same height. The Attack's are 24 mm heel and 21 mm toe. They have a binding delta of 3 mm. I prefer zero delta, so the PRD's are the better option for me.

I think I know why the PRD's have to move more forward. The Attacks have no plate so the toe weight (force) goes directly to the ski under the AFD. For the PRD's, the toe force goes into the AFD, then into the "plate" then into the ski. The plate will spread the force out a little, with the effect being to move the "center of force" more rearward. Hence you have to slide the binding more forward to get the same "center of force" to the ski.

Time to get out of my physics comfy chair.

I looked up the heights of the bindings:

Attack AT 24/21 Heel/toe
Attack GW 17/14
PRD 12 GW 33.5/33.5

This might be older info, not sure about current binding numbers

Not quite sure where you are getting your numbers. Mine are from direct measurements when mounted. Note that they differ a bit from the "official" published numbers.

PRD GW: 3.5mm delta
Attack: 3.0mm delta

There is no PRD to my knowledge that has a flat delta. So I am wondering about your measurement method. Unless maybe you actually have GripWalk boots and are using the binding in GW mode?

I'm also not completely following the physics you're describing for the application of pressure being different between these bindings. It sounds like your claim is that the rail of the PowerRail reduces the immediacy of the power transfer. However, how does this really move the force more "rearward" as you say?
 

ScottB

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My boot size is 29.5. I tend to mount on the line or 1 cm behind the line. If we assume the reference size is 27.5, that says you should mount .5 cm in front of the line. Most of what I am saying is boot size can dictate a shift in mount point. Independent of skier size/weight. Its just about length of foot and and the position where the skiers weight is transferred to the ski.

I think everything you are saying is true. Basically moving the binding back and forth by experimentation is the best way to find the optimum mount point. A lot of skis aren't that sensitive, so mounting on the line works fine, but it ignores the differences in length of the foot.
 

ScottB

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Not quite sure where you are getting your numbers. Mine are from direct measurements when mounted. Note that they differ a bit from the "official" published numbers.

PRD GW: 3.5mm delta
Attack: 3.0mm delta

There is no PRD to my knowledge that has a flat delta. So I am wondering about your measurement method. Unless maybe you actually have GripWalk boots and are using the binding in GW mode?

I'm also not completely following the physics you're describing for the application of pressure being different between these bindings. It sounds like your claim is that the rail of the PowerRail reduces the immediacy of the power transfer. However, how does this really move the force more "rearward" as you say?

Noodler,

Here are my measurements: (made with a caliper)
Attack13: 24.4mm / 21.3 mm R/F
PRD: 35.3 / 34.3 R/F

I measured from the ski top surface to the top of the binding pad where the boot sits. I did not put the boot into the binding, so I might be off in my measurements.

For the PRD, the toe is not on the ski, it is on a "powerrail" so the the weight force has to transfer from the binding to the rail to the ski. When the force transfers to the rail, it won't go straight through, the flex/deflection/beam properties of the rail will shift the position of the flex. I expect it will typically move rearward, toward the other mount point. I would need to do a FEA analysis to get a real number. The real world experience Otter 2 described says it moves rearward and that is the direciton I would expect.
 

ScottB

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Its late, I will try to explain better tomorrow. I am trying to simplify my engineering force analysis thinking, and not doing it to well.
 

Uncle-A

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I think we have thread drift with all this talk about binding position and height. When all the OP wants is a little help with the choice of the length of the ski.
 

James

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Well it's relevant. Have you skied the 182 vs the 175 or 168? Very different.
 

François Pugh

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Well it's relevant. Have you skied the 182 vs the 175 or 168? Very different.
Yes, it is relevant.

Caveat, I'm not 230 lbs, and I have never skied the Stockli AX, but I have noticed a few things.
1) At 230 lbs and an expert skier, the OP should be on the longest length, yet he prefers the 2nd longest length in his other skis.
2) A longer ski would maximize the skis performance on softer snow and on bigger hills out west (bigger platform, more float, higher speeds, longer turns etc.).
3) A shorter length would maximize the skis performance on hard snow groomers (more edge pressure and all that).

Considering that the AX is an all-mountain ski (with a 1.3 degree base bevel :eek:) and not one of Stockli's hard snow carving skis, it seems best to maximize its performance in its area of strength, i.e. get the longer ski at 182.

Now, there's no accounting for taste, but the OPs taste tends to run a tiny bit shorter than would seem normal. Therefore mount, the 182 about 1/2 an inch forward to make it seem shorter, but not too much forward (enough to make a difference, but not enough to alter behaviour drastically and also enough that if he doesn't like it he can remount at the line without hole interference).
 

ski otter 2

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Fortunately, with an adjustable binding, the OP or @ScottB can adjust the mount point to find his favorite spot(s) for skiing different conditions and locations. With this particular ski, at the longer length in particular, such choice matters. Also, the 175 length of this particular ski behaves like a 180/18 cheater GS ski, in my experience: great edge, very quick from edge to edge in similar fashion. Such skis are also good in bumps. The next longer size isn't, anywhere near as much. If he's a bumper, or quick-turning on groomers, the OP might enjoy that quick 180/18 feel the shorter AX has.


With apologies to the OP,
I definitely used the Head/Tyrolia PRD 12 stand alone binding, no plate, on my 17/18 Laser AX 183. So it is on the power rail.
(On this particular binding, this time) toe 29.5 mm., heel 33 mm.

(All measurements are approximate, by whatever method(s) I've found most accurate. I've done no adjusting of the bindings to various modes or norms, so with adjustments, where possible, some of these might change a bit.)


Two previous PRD 12 Tyrolia/Heads I measured some months ago, in a shop: toe 30, heel 32/33.
(I ended up approximating my different heel measurements as between 32 and 33.)
(Others measured these also at the same time; some got the same, some got slightly different measurements than mine.)

There is also a PRD 12 MBS (Multiple Boot Standard) that Head/Tyrolia gives a single published 33.5 overall height to, no published delta included.

Also a Head/Tyrolia PRD GW, with a published single height of 35.5


A standard Attack2-13 demo binding: toe 21 heel 23
(two used versions I have measured the same, approx.)
I got the same approx. measurements off a new pair being sold retail in a ski shop, thus a third example. These were not AT versions, so that may account for your different measurements on what I gather is your Attack2-13 AT demo version, @ScottB . Your particular version is probably a retail demo version, not the same as my friend's. (See below, next binding.) Variations on factory runs, different year or different norm models unmarked could also account for these being different from @ScottB measurements. Also, with or without calipers, it's plain hard to figure out the best spots to take measurements from on the slanted surfaces of toe and heel, hard to fit calipers into receded, uneven, inaccessible spots, etc. And different operators will make different choices here, trying to stay consistent, at least with themselves, but harder with others at a distance. Approximations, whatever the tools or methods!

The particular Attack2-13 AT demo binding on my friend's 17/18 AX 183: toe 30 heel 32.
(Note: It's from maybe two or three years ago, at this point. It is to some degree a specialized performance shop wholesale demo binding, not a retail or a rental demo binding. [They are all different.] This model has to be a special order by a demo rental shop with leverage, and it is not generally available to sell to the public, but only, eventually, as part of a used demo package, once the demo ski is discarded and for sale used after a year or two. I found it is written into many brand-to-demo shop contracts that this binding cannot be sold stand alone retail, but only sold used as part of a used package later on. And this is standard industry practice with this whole class of bindings, across a number of brands. Some shops are exempt from such contracts because with volume they have leverage.)

There is also an Attack2-13 retail demo binding, and a retail version also that is AT now. By your measurements, this is probably the AT binding you have. These are not the same as the wholesale performance shop version my friend has. (His came from Gorsuch in Vail, and he got it because he is in the business.)

There is also an Attack2-13 GW Demo, with a 32 mm single height published. I measured a version new in a shop at toe 30, heel 32.

Again, all measurements approximate!

I suggest getting used to using the term "approximate" when measuring binding height differences, and even if there are published measurements released by the Brands themselves. (Rare.) Maybe just relax with it, work with it - find "work arounds."



I went into such detail partly to make a point: to show the kind of amazing variations in binding models, and thus one of the real obstacles to getting a firm grip on measuring binding delta specs, just to get some relaxing and forgiveness in such discussions.

By our rough count, there are some 150 to 250 new, everchanging retail binding models being sold in shops now from just the four major brands. Many have the same names but have unannounced redesigns or modifications, others are unsold last year's stock, mixed in with stock from previous years - all still getting sold out of brand warehouse inventory, and still being sold "as new" in ski shops. Still other binding models are for different specific purposes (besides all mountain: race skiing, near-race skiing, backcountry, skinning, trekking, child, junior, female, non-retail cheap demo bindings for rental/lease, non-retail more upscale demo bindings for rental and some demo, non-retail performance ski demo bindings, retail sale demo bindings, etc.) This is not counting versions no longer being sold, but everywhere on the slopes, which need knowledgeable repair and replacement at times, so might need to get measured for height also. It is not practical to use complex cut-outs or model-specific measuring aids for such a steady, ongoing stream of different, often slightly unidentified binding variations, coming into and out of shops. Instead, a quick, handy way of measuring height toe/heel differences is necessary, however faulty it might be, along with a process for dealing with approximations - and some practice with different bindings. Choose your tools and methods.

Along these lines, a bunch of us in a ski shop played with accuracy in these measurements. Without going into detail, just cutting to the chase, we realized we had to choose our tools and methods somewhat subjectively (a bit like choosing ski poles), and got used to approximations.
 

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