Fore/aft binding placement

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Fore/aft binding placement

Postby Hobbit » Thu Apr 22, 2004 5:32 pm

I would like to discuss the fore/aft binding placement issue and seek your feedback and opinions. I suggest that you read an excellent series of articles on this subject published by Peter Keelty on the RealSkiers WEB site.

In brief, the maximum ski bending sensitivity would exist when your body weight is applied to the ?bending? center of the ski. As the article mentions, different manufacturers place the bindings in different spots in respect to fore/aft alignment even for the similarly shaped skis. The binding placement is also similar to the boot alignment process since every person is different in respect to their fore/aft ?neutral point? location. Of course you may correct fore/aft position by moving your legs or body but the best initial condition exist when you are centered on the ski in the first place. Otherwise you would have to apply muscle efforts to continuously offset your ?neutral? position to the match the ski ?neutral? position.

Peter mentions few methods allowing for correct fore/aft binding placement. I don?t want to re-type all this information here (you can look it up yourself). He mentions the traditional ?ball of the foot? method and alternatively using the Campbell Balancer device. Honestly, I don?t understand the physics behind the ?ball of the foot? method. I feel that it might be OK for the straight skis, but modern shaped skis have different width for the tip and tail so the middle of the ski is not necessarily the actual ?bending center? point. Since the stiffness and the bending characteristics of the skis do vary a lot I am willing to trust the manufacturers ?middle mark? point on the ski.

The individual skier fore/aft ?neutral? point is of more interest. I studied the info on the Campbell Balancer including the patent which covers it. In essence, it?s a tipping board. So I decided to use the tipping board which I made for balancing exercises to measure where my fore/aft balance point is. Instead of lateral balancing on the board while standing on one foot (normal usage) I stand on it with both feet and balance in the fore/aft direction. I use a small mirror which I place on the floor next to the board to see where my boots are in respect to the center mark line on the tipping board after I assume the "skiing" body position and try to find a balance point.

I think that ideally the boot ?center mark? should match the center mark on the tipping board when you are assuming correct posture and reach the balance. I found that my balance point is reached with the middle mark on the boot approximately 20 mm ahead of the center mark on the board. I was constantly in the back seat. Since I am using Atomic bindings which are really easy to move fore/aft, I moved them 20mm forward. If you decide to repeat my experiment, I also suggest that you try to move the binding fore/aft a little bit (like 5 mm) around the new ?measured? point in order to find the exact binding position. The tipping board measurement method is not as precise as the Campbell Balancer but I believe that it will give you a pretty good idea in our particular situation.


I am very happy with the results and feel a big difference this adjustment made in my skiing. I think that fore/aft binding placement is especially important for PMTS ? based skiing since we rely mostly on tipping and edging, which in the end results in bending the ski.
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Center point with Tyrolia rail flex

Postby JimR » Thu Apr 22, 2004 6:48 pm

Hobbit:

I did something similar with my Head ic160's and super railflex bindings (which makes it easy to adjust fore and aft) this year. I experimented this year with various settings between the factory recommended 0 setting, + 15mm, and +30 mm (by changing the binding to rail attachment points). Overall, I felt a lot better balanced at +30 (which, for me, matched Peter's concept of center of running surface under the ball of my foot).

As you know, Peter's articles do indicate that both Atomic and Head have some of the most rearward recommended mounting positions, as opposed to most of the Frence models. I also believe there are at least three shops still using the Campbell balancer (Snowbird, Chicago, and Washington DC).
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Postby tommy » Fri Apr 23, 2004 6:52 am

Hobbit,

when I got my new atomic sl9's few months ago, I did the first few runs with the binding in the default "normal" place. However, I found turn initiation more difficult than expected. So I pushed the binding forward, to the "extreme" mark, and could immediately notice the difference.

So those few cm's really do matter. I talked about this with Peter K. and his recommendation was to move the binding even further (by remounting it), but I havn't bothered to do so, since I feel quite comfortable with the skis as they behave now.

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fore and aft - why do manufactureres to that

Postby John Mason » Fri Apr 23, 2004 7:17 am

fore and aft - why do manufacturers to that

I have head I75m's and in their manual they say move the binding forward if your a beginner and back if your an expert. So, what will most people do? They'll say to themselves I'm and expert so move the binding back.

But, this makes the tails shorter vs the fronts which means given even pressure on the ski or edge engagement that allows for a brushed carve, you will end up with the tails sliding more than the front.

Perhaps manufacturers put the placement further back to make the skis less likely to carve and easier to slide the tails out to match the way most people turn the skis.

But if that's the case why would head in their literature say move it back if expert and forward if beginner?

Or - is the binding placement being to far back and more back for an expert based on the old idea that you pressure the tips to turn in order to get the ski to bend into an arc. Thus, the further back, the more the ski will react to forward preassure. In good skiing you pressure the center of the shaped ski and because it's shaped it will bend and increase the carve.

So, I would submit that Head's thinking is in deference to old style, press the tips to bend the ski, expert skiing. Since an expert wants shorter radius turns than a beginner, thus their manuals instructions to move the bindking mount back since Head's people think experts want to turn by tip pressure.

I find this ironic since that ignores the fact these are shaped skis and harkens back to the ski methods of straight skis.

In other words - for people reading this discussion that may not have thought about it - in PMTS we stand more on the foot to pressure the ski to bend more and tighten the arc. (if you lighten and tip the inside foot more, this additional weight on the outside ski will happen as a result also) In traditional sking you press forward into your boot to bend the tips to tighten your arc. Thus the two sking philosophies that result in Head's convoluted instructions and binding placement vs where we would like it to be.

A side effect of this difference is that the futher the binding is placed back, the easier it is to ski wrong and slide your tails around.

Given the above discussion, I'm not sure simple balance would be enough as that assumes the flex of the ski is the same front to back which due to design differences may not always be true. I would think the spot would be were the ski bends neutrally so that if the ski was mounted on only it's back and front tips and you press down on the ski at different points, where is the bending point where the front and back of the "test foot" pressures the same as opposed to pressure being felt on the toe or heel end of the foot, yet still bends the ski evenly.

I'm not saying this well. I'm trying to describe that where a ski balances alone leaves out the skis dynamic characteristics. To illustrate my 6 stars and head I75m's from the factory binding settings feel totaly different in fore and aft balance. The head's binding must be moved forward to even begin to approach the more centered feel of the 6 stars. Yet the overall binding position on both skis is similar. So, I'm not sure balance alone would do it as compared to dynamic bending analysis.

Bottom line, I'm not sure there would be any substitute to playing with binding placement on the slopes to see where you are neutral and where the skis carve best. This may or may not be where the balance point is as simple balance leaves the bending design of the ski out of the picture. That can vary by the structure of internal railing or stiffeners, variable widths, etc. I know of no shaped skis that are symetrical hour glasses shapes.
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Postby Harald » Fri Apr 23, 2004 7:21 am

Since I began skiing on German and Austrian skis I have experimented with moving the binding forward. One day at a magazine test, which I used to do, I stopped and skied Volkl skis for two runs, because I moved the binding forward after the first run. Normally they don?t let you test the skis twice. I discussed it with the editor and he agreed. The skis skied much better further forward. I talked later to the product manager for Volkl and he was incredulous.

Since I have skied with Head, I move all bindings forward except on the race skis. I was formerly not in favor of moving bindings forward when I skied on K2, as they don?t work well with pressure further from the tail. I have tested binding location with hundreds of our clients in camps on Head. Over ninety percent agree, they found the skis easier to ski in a 1cm to1.5 cm forward position.

It took me two seasons to get the reps at Head to move the test skis forward. They finally did it this year. Most of the reps and product managers are very traditional and they don?t like to go against the manufacturer?s recommendation, so you may not be getting the best information from them. I ran into one situation where one of our skiers liked the iM70 centered. With the railflex bindings from Tyrolia, it is very easy to move the position. If you are not sure about the ski?s performance move it one position back or forward.
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Postby jclayton » Sat Apr 24, 2004 12:18 am

How exactly is the performance enhanced ?

less forward pressure needed to turn ? More stable ? better in bumps ? Powder ?

J.C.
skinut ,among other things
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Postby Harald » Sat Apr 24, 2004 3:30 pm

Skis with well placed bindings feel like they turn from the middle. Skis mounted too far back feel like the tip is too long.
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Postby Coach » Sun Apr 25, 2004 7:20 am

Harald

I just pick up a pair of Volkl AXE 4's. How much forward would you recommend the bindings be placed in terms of +MM (ie +10 mm, + 15mm, etc.). Thanks in advance for your help.
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Postby Harald » Sun Apr 25, 2004 12:22 pm

Caoch, how long are the skis? You can try 1cm forward normally it will make the skis more active.
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Postby Guest » Sun Apr 25, 2004 2:14 pm

Harald wrote:Caoch, how long are the skis? You can try 1cm forward normally it will make the skis more active.


They're 178cm. Dimensions are 118-83-106. Let me know what you think.
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Campbell balancer approximation

Postby JimR » Sun Apr 25, 2004 10:05 pm

In his articles on the cambell balancer and the study they did at Snowbird regarding binding placement, Peter provides a general rule of thumb for binding placement; i.e. placing the ball of the foot over the center of the running surface of the ski (his articles describe how to do all of this). I sort of agree with John Mason that this seems to simple, that it ought to be more complicated and influenced by the design and sidecut and design of the ski. However, I have to admit that where I wound up on my skis this year is pretty close to what Peter's guidelines indicate.

Harald, do you agree with Peter's gross rule of thumb (for those cases where a balancer isn't available)?
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Postby Hobbit » Mon Apr 26, 2004 8:19 am

In my opinion these two methods contradict each other.

The "ball of the foot" method does not take into consideration how your weight is distributed and applied to the ski. It's just a measurment of mechanical dimentions (where your feet is corresponding to the ski).

The ballancer method attempts to discover your individual position which is a product of your body weight distribution, stance and probably boot geometry (lean angle).

My main point in the original post was that you can do a simple test similar to Campbell Ballancer test using the tipping board. If this test works, than I expect to see that some people need to move bindings fore and some need to move it aft. The offset should be individual and based on the measurment.
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