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Suggested mounting line (how do manufactures choose where to put it)?

post #1 of 16
Thread Starter 

This is a question that I posed in the Tuning and Maintenance section, but I thought it might get a little more attention here.

 

Why are suggested mounting lines different on different skis of the same length?  For example, the line on my Rossi E100 (182) is about 3cm forward compared to my FIS GS skis (183).  In other words, my all mountain skis have less tip and more tail compared to the GS skis, if mounted according to manufacture specifications.  Anyone have any thoughts as to why this is?  I would have thought that the all mountain skis would have the line further back than GS skis...

 

Thanks!

post #2 of 16

Good question.  In the old days, the rule of thumb was the toe of the boot was at the center of the ski.  Just measure from tip to tail and find the middle.  Rocker changed everything.  I think they try to put the ball of the foot in the center of the running length of the ski.  So a ski with tip rocker but little or no tail rocker would be mounted farther back.  I'm sure there are other factors that come into play, but I'm not clear on what they might be.

post #3 of 16
Thread Starter 
Quote:
Originally Posted by JimH View Post
 

Rocker changed everything.  I think they try to put the ball of the foot in the center of the running length of the ski.  So a ski with tip rocker but little or no tail rocker would be mounted farther back. 

 

This is why I'm so confused: the mounting position on the tip-rockered E100s is way FORWARD compared to the GS skis.  Again, it would seem (like you said) that the mounting position would be further BACK on this type of ski.  I'm honestly perplexed!

post #4 of 16

How do they select the mount point? Testing.

 

Why is an E:100 forward of a GS race ski? The E:100 has tip and tail rocker, not just tip rocker. A wide all mountain ski (100mm is more soft snow oriented than hard snow oriented, believe it or not) is built to be skied with a more neutral balance and softer 'touch', the FIS ski is designed to be driven from the front of the ski boot. This difference means the GS ski gets more shovel and the all mountain gets less. Think of where your center of mass is if you are standing neutral in your boots vs driving forward flexing the boot, transpose that CoM to a ski, are you starting to get a visual? 

post #5 of 16
Thread Starter 

Okay, I can see that: the more forward-driven a ski is designed to be, the more shovel length it should have to balance out the more-forward CoM.  In other words, the guy/gal who drives the ski, and thus has a more-forward CoM during the beginning stages of a turn, has less shovel in front of his/her CoM as compared to a skier who is in a more neutral stance. That makes sense and I buy it.

 

How about skiing styles as having an effect, then?  Would a skier who is more naturally-inclined to drive a ski want to consider mounting a bit further back on an all-mountain ski?  I obviously don't drive my all-mountain skis quite as hard as I do my GS, but compared to other skiers, I think I'm more on my toes/ball of foot no mater what I'm skiing.  (Indeed, one of my more embarrassing moments was when I had spent almost an entire season on hard-pack and went to visit my brother in Utah, where it had snowed 18" the night before.  My first turn into a bowl, I dug my tips in and just somersaulted.  Oh, did my brother have a chuckle!).  I'm pretty sure given my style, I'm going to mount my E100s 1cm back.

post #6 of 16
Quote:
Originally Posted by AlbuquerqueDan View Post
 

Okay, I can see that: the more forward-driven a ski is designed to be, the more shovel length it should have to balance out the more-forward CoM.  In other words, the guy/gal who drives the ski, and thus has a more-forward CoM during the beginning stages of a turn, has less shovel in front of his/her CoM as compared to a skier who is in a more neutral stance. That makes sense and I buy it.

 

How about skiing styles as having an effect, then?  Would a skier who is more naturally-inclined to drive a ski want to consider mounting a bit further back on an all-mountain ski?  I obviously don't drive my all-mountain skis quite as hard as I do my GS, but compared to other skiers, I think I'm more on my toes/ball of foot no mater what I'm skiing.  (Indeed, one of my more embarrassing moments was when I had spent almost an entire season on hard-pack and went to visit my brother in Utah, where it had snowed 18" the night before.  My first turn into a bowl, I dug my tips in and just somersaulted.  Oh, did my brother have a chuckle!).  I'm pretty sure given my style, I'm going to mount my E100s 1cm back.

Sounds like you might want to either (a) get moveable bindings (e.g., Marker Griffon Schizo); or (b) rent a demo of that ski early season and, using the demo binding, find your optimum mount point.  Though if you do the latter, be sure to note the delta on the demo binding compared to what you plan to mount -- even 2 mm can make a noticeable difference.

 

Also, as Whiteroom says, the mfrs. determine mount points with testing.  However, let me add another wrinkle:  this means that individual manufacturers might be biased towards slightly rearward or forward mounting points, based on the biases of their testers.  I.e., if you gave two diff. mfrs. identical skis, the two could well arrive at diff. recommended mount points.  

post #7 of 16
Quote:
Originally Posted by AlbuquerqueDan View Post
 

Okay, I can see that: the more forward-driven a ski is designed to be, the more shovel length it should have to balance out the more-forward CoM.  In other words, the guy/gal who drives the ski, and thus has a more-forward CoM during the beginning stages of a turn, has less shovel in front of his/her CoM as compared to a skier who is in a more neutral stance. That makes sense and I buy it.

 

How about skiing styles as having an effect, then?  Would a skier who is more naturally-inclined to drive a ski want to consider mounting a bit further back on an all-mountain ski? 

 

 

IMO you've kinda skipped from the metaphorical ankle to the metaphorical waist of the reasoning chain there.     Before we talk about skiing styles, shouldn't we talk about such things as ski flex and how that flex interacts with the sidecut to actually engage the edge?     

 

I see no reason to assume that mounting >random number of cm< back is going to be at all functionally enabling on a given ski, let alone functionally equivalent amongst different skis enough for us to talk about it in general terms like in this thread.

 

IOW, chances are you can get away with mounting your E100's  1 (or whatever number of) cm back, but then that and most other mass market commercial skis are designed to have a relatively wide use envelope.     But there are definitely instances where that envelope may not be broad enough for your reasoning to work the way you expect it to.    

 

For example, somewhere on this forum is a thread about how much I hated the Elan Apex when it first came out.    I see now that that ski's flex simply wasn't sufficient for someone my size to drive the front of the boot, no matter where the mounting point was.    No matter where the mount point was, unless I skied completely neutral I would have the 'tips digging in sensation'.    Except the tips weren't digging in - the ski was flexing in front of the binding.    Enough to make me heel release.   On hardpack.      I could have made equivalent threads about some other all-mountain skis with narrowass flex/sidecut envelopes (*cough*CoreUpt*cough*) but the forums are somewhat past listening to me be negative about their halo babies.

 

 

 

post #8 of 16

With regard to a old non-rockered ski powder ski, the Legend Pro XXL, Dynastar used to tell dealers that 78cm from the tail was the "powder stance" and 82 cm from the tail was the "race stance".  By the end of the product run they started putting a "recommended" mark at 80cm.  The consensus among people who skied them was that 79.5 was the best.  

 

I'm thinking the idea of having a bit more tip was to keep dive in deep snow to a minimum.  With rocker and tip shape changes, tip dive is less of a problem so the benefits of a more forward mount (easier initiation, easier 360's, etc) can be realized and the recommended mark has moved forward.

 

On my SL skis, I'm able to move the binding +/- 3cm and they are very different at each setting.  Moving them back makes them calm at high speed and moving them forward makes them very "turny" and easier to ski slowly and hook-up on ice is improved.  I wonder if the rearward recommendation on your GS skis might have something to do with the speeds those skis are designed to perfom at.

post #9 of 16

Talking of Dynastar, the Chams would be easy examples of skis where forward/rearward mounts are not particularly predictable, whereas skiing from the front of the boot or neutral are both fun in completely different ways.       

post #10 of 16
Thread Starter 
Quote:
Originally Posted by cantunamunch View Post
 

 

IMO you've kinda skipped from the metaphorical ankle to the metaphorical waist of the reasoning chain there.     Before we talk about skiing styles, shouldn't we talk about such things as ski flex and how that flex interacts with the sidecut to actually engage the edge?     

 

 

 

Respectfully, I don't think I'm putting the cart before the horse here.  My question about skiing styles was about mounting a particular ski (e.g., the E100) a bit forward or a bit rearward depending on the skiing style of the person for whom the ski is being mounted.  In other words, the only variable I was talking about was the skier (whether he tends to drive a ski, ski neutrally, or ski in the backseat).  

 

Maybe a clearer way of asking the question would be to set it up as a thought experiment: My identical twin brother and I just bought the E100 @ 182 and plan to mount them with Solomon STH2 16s.  We have different skiing styles, having focused on different skiing priorities: I was coached as a GS and slalom racer and tend to drive the ski and make high angulation turns.  He has been a big mountain guide in AK and tends to slarve more turns and have a neutral stance.  These traits influence the way we ski everywhere, not just in the gates or on the knife ridges.  Now, fate has brought us together again and we are both planning to ski our new skis at the same ski area on on the same days on the same terrain.  Given our two different skiing styles, should we mount our bindings differently?  If so, what would those differences be and why?

post #11 of 16

In 2008, I posted a thread here specifically concerned with effect of mount point, using a Gotama with Railflex bindings: http://www.epicski.com/t/69037/effect-of-mount-point-on-gotama-performance

 

IME these days, most manufacturers that make freestyle or freeride skis now routinely offer two mount lines, either on the ski or via an email. Rossi, for instance. The "freestyle" or "normal" line is 0, the "directional" line typically is -2. That implies that they assume directional skiing involves more boot pressure and forward lean. Which may be true on average, doubt it's a very tight correlation. 

 

And my guess is that "testing" is not what it sounds like. It's not "optimal performance." Rather, each ski has its target demographic, established by marketing. So an intermediate carver will have a different set of criteria applied to its mount line than a GS or a Stockli 107. My hunch is that they move the mount line more foreword by decreasing target level, since a forward mount decreases the effective running length ahead of the boot, makes the ski easier to turn, and in any case, most skiers, even good ones, get our weight too far back some of the time. More tail helps with recovery. The only skis I know of that have lines assuming you're projecting forward all the time are FIS racing models. 

 

In fatter skis, with a target demographic that values neutral stances, taking air, sometimes skiing switch, I'd assume the placement of lines at ski center is to optimize that, not the ski's envelope at speed or on packed snow. 

 

Another question is, "Does it matter?" I'd guess that our own error, meaning the variance in how far forward or backward we are in a given run, or in different snow the same day, washes out any 1 cm difference. Mount point may best measure how consistent we are...

post #12 of 16
Thread Starter 
Quote:
Originally Posted by chemist View Post
 

Sounds like you might want to either (a) get moveable bindings (e.g., Marker Griffon Schizo); or (b) rent a demo of that ski early season and, using the demo binding, find your optimum mount point.  Though if you do the latter, be sure to note the delta on the demo binding compared to what you plan to mount -- even 2 mm can make a noticeable difference.

 

So I did option (b) today -- except it was with an E88 rather than an E100 -- and tried center, 1cm back, and 2 cm back.  Here's what I noticed: the ski mounted at center was easier to release and seemed quicker to engage a turn; the ski at 2cm back felt more balanced, more solid, and stronger holding an edge.  The center mount was a bit better in the moguls, but much worse at carving strong turns.  Said simply, the center mount was easier and the rearward mount was stronger.  I decided to mount my E100s 2 cm back.

 

HOWEVER, Chemist, what you say about delta has me a bit worried now.  The demos had the Axial 120s and I'm mounting with Solomon Sth2s.  It felt to me that the Axials had a lower angle than the other bindings I ski on (all FIS-compliant, either Rossi or Tyrolia).  Do the Axials have a lower delta than race bindings?  It sure felt like it!  How about the Sth2s -- anyone know how they compare to the Axials with regard to delta?

post #13 of 16
Quote:
Originally Posted by AlbuquerqueDan View Post
 

 

So I did option (b) today -- except it was with an E88 rather than an E100 -- and tried center, 1cm back, and 2 cm back.  Here's what I noticed: the ski mounted at center was easier to release and seemed quicker to engage a turn; the ski at 2cm back felt more balanced, more solid, and stronger holding an edge.  The center mount was a bit better in the moguls, but much worse at carving strong turns.  Said simply, the center mount was easier and the rearward mount was stronger.  I decided to mount my E100s 2 cm back.

 

HOWEVER, Chemist, what you say about delta has me a bit worried now.  The demos had the Axial 120s and I'm mounting with Solomon Sth2s.  It felt to me that the Axials had a lower angle than the other bindings I ski on (all FIS-compliant, either Rossi or Tyrolia).  Do the Axials have a lower delta than race bindings?  It sure felt like it!  How about the Sth2s -- anyone know how they compare to the Axials with regard to delta?

I don't know if what you found with the E88 will translate to the E100 -- maybe someone here that's familiar with both skis can weigh in.

 

Regarding deltas, maybe someone here can give you those specs., but that info. can be hard to find. Often one needs to contact the manufacturer, unless you can find a technical manual (you could try searching online for this).   And even if you can find that info., the manufacturer's specs can be funny.  That's why I just measure them myself.  I use a set of digital calipers (I also have a jig that allows me to rigidly mount a digital inclinometer to my ski boot, but never mind :rolleyes).  But you can get away with a ruler (though a ruler and a T-square is better).  Just mark the side of one boot at the points where the contact of the sole with the ground ends (i.e., where the sole loses contact with a flat surface), click the boot into the binding, and measure the distance from the bottom of the boot to the bottom of the ski at each of those points, and subtract (easier than going from the bottom of the boot to the top of the ski, since the edge of the top is rounded, but it does assume the ski's thickness doesn't change significantly between toe and heel, which is generally the case).  You can do this in the shop from which you rented your skis.  If you stay out of the way they won't mind, and indeed might even be curious themselves and want to help.

 

The good news is that, if the bindings you'll be using are in fact more tilted than the Axials, that would be like moving you forward (not exactly, but in the same vein), yet you decided to err in the direction of moving yourself back.

 

I also wanted to comment specifically on this:

 

"The demos had the Axial 120s and I'm mounting with Solomon Sth2s.  It felt to me that the Axials had a lower angle than the other bindings I ski on (all FIS-compliant, either Rossi or Tyrolia).  Do the Axials have a lower delta than race bindings?"

 

First, FIS doesn't have specifications for delta, just for maximum stand height (for ski+binding+boot together), so FIS compliance wouldn't be relevant here.  In addition, there is no standard delta for race bindings -- they can vary quite a bit.

 

The nice thing about delta is that it is adjustable (unless you have one-piece system bindings), and you don't need to re-drill the skis.   Just ski on the ski, and if you feel like you're tilted too far forward (like you have to sit back to be balanced), first have you're boot alignment checked, and if you still feel that way, have the shop put a lifter under the toe of the binding.  Conversely, if you feel like you can't get forward on your skis, you may (again, after checking boot alignment) need a lifter under your heel.  Indeed, I wonder if you could do a dry-land test for delta in the shop, by putting shims of varying thicknesses under your heel, and seeing where you feel balanced (or under the toe, if you need a negative delta).


Edited by chemist - 11/29/14 at 7:15pm
post #14 of 16
Thread Starter 

Thanks, Chemist: yeah, I know that the 88s and the 100s are different skis.  However, I think the mounting position will be analogous in that they both have the same camber profile.  We'll see, right!?!

 

As for FIS and delta regulations, you're totally right, I just figured FIS had made standards for that, too.  Actually, I'm surprised to hear they haven't!  I did not like the way the Axials felt, especially combined with the fact that my new boots (Dalbello Scorpions) are more upright than my old boots.  I'm used to being in a more aggressive stance from then get-go than I was today (although, it was GREAT to be back on snow after the long, hot summer!!!). 

post #15 of 16

Why not just get the Marker Griffon Schizos and save yourself all the worry?

 

It wouldn't make sense for FIS to regulate delta -- it has an entirely different nature from stance height.   With stance height, there was an arms race to go higher and higher, and FIS wanted to put a stop to that.  Delta is entirely different.  Here the racers are trying to dial themselves into the angle that gives them the optimum balance, so they aren't going to more and more extreme deltas.  I would hazard a guess that the overwhelming majority of binding deltas on the world cup are between -3 mm and +7 mm. [I'd be curious to know what the actual range is.]

post #16 of 16
Thread Starter 

Well, after (over)thinking the matter, I called the shop to have the skis mounted center.  I liked the rearward mount on the 88s because of the stronger tail.  Because the 100s have more tail than the 88s, I erred on the side of a more playful mounting location.  I can't wait to review these bad boys!!

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