BoF Mounting Point Method for the 21st Century

<decided that this now needs to be first and it has been edited for clarity>

EDIT P.S. - I have decided that this method does NOT work with funshape/5-point designs.  I believe that it can work well for traditional, multi-radius sidecut, and early rise designs.

In the last few years it has become readily apparent to me (and others) that the current thinking revolving around BoF (Ball of Foot) over CRS (Center of Running Surface) mounting point determination was incredibly inaccurate for today's advanced geometry skis.  With skis sporting dual/triple radius sidecuts, klothoid designs (Palmer), early rise, rocker, and full-on funshapes (S7, Wailer 112RP, Obsethed, JJ, etc.) trying to use the CRS in any determination of the mounting point is an exercise in futility.

So here I present my latest incarnation of determining a binding mount position based on placing the BoF in an ideal location on the ski - hopefully on the sweet spot for you.  I hope that this thread does not devolve into an argument about the merits of BoF mounting positions versus the manufacturer marks.  That has been done to death.  What I would like to see is an intelligent discussion regarding the merits of this process (both pros and cons) from those who advocate or are at least interested in the concept that there is no one single mounting point on a ski that will work for every person's morphology.

THE PROCESS

As a refresher here is what I'm currently doing to determine the distance from the BoF to the midsole mark.

Determining the BoF to Boot Midsole Mark Adjustment Length:

1. Stand on a hard surface floor in your bare feet.
2. Go up on your tip toes (only your toes and BoF are in contact with the floor).
3. Slide a thin business card along the floor up to your foot from the rear.
4. The business card will stop where your BoF meets the floor.
5. Lower your feet being careful not to shift the position of the card.
6. Use a pen and mark the point on your foot where the business card edge stopped.
7. Measure the length of your foot (this could be done on a Brannock or carefully by backing your feet up to a flat wall and marking where your toes end).
8. Find the midsole of your foot (half the length) and mark this position on your foot.
9. Measure the distance from your BoF mark to the foot's midsole mark.
10. This value is your BoF to Midsole adjustment (for me this is 56mm).

Note that I use a digital caliper for the measurements and it can be helpful to have someone assist you in placing the business card and getting your foot measurements, as trying to do these measurements yourself can slightly alter the true values.  Also, I should point out that I have a VERY tight shell fit now (dropped down another shell size).  My foot is literally exactly the length of the bootboard and I have about 5mm shell fit.  So my foot's midsole is very close to corresponding to my boot shell midsole mark.  There have been plenty of other methods published on how to find your BoF and figure out where it hits in your shell (i.e. the shell tapping with a hammer method, etc.).  Just note that your foot is never "seated" in the middle of your boot when you're buckled down - it's always pushed to the rear, so any "free" space in the shell length fit is mostly in front of your toes and would need to be accounted for in determining your own BoF to Midsole adjustment length.

Now we move on to the significant change to the previous method of determining the binding mount position.  There is a summary of the steps below for those who wish to ignore the detail of the method and how I arrived at devising it.  Instead of using CRS I am now using the Center of Effective Edge (CEE).  My reasoning is basically this - what amount of the ski surface that rides on the snow when it is flat is of little consequence.  I started wondering why we would even care about a flat ski.  What we're really after is how the ski acts and reacts when we have it on edge.  Considering the ski when it's on edge has the effect of "equalizing" some of the more complex designs available.  I'm certainly not going to say that this is a cure-all and infallible for every crazy design out there.  I haven't done nearly enough testing to hang my reputation on that shingle.  What I am saying is that using the effective edge of the ski will result in a more realistic determination of a mount position based on how skis are actually designed to be used - on edge.

After deciding to go with Effective Edge, I researched exactly how the EE is determined.  Unfortunately I ran into many opinions on what constitutes the Effective Edge and how to determine it and measure its length.  True Effective Edge as I understand it is the length of the edge that can come into contact with snow in a turn and be utilized - generally hardpack is assumed.  However, most manufacturers that do list EE (including many snowboard makers) use the absolute extreme value for EE found when the ski/board is 90* on edge.  I don't know about you, but I never get my skis to 90* on edge .  So that left me in a position of having to decide just how much edge angle to assume when developing the new method.  I settled on 45*.  You may argue that it really should be 60* (for very aggressive racers who regularly achieve high edge angles) or some might say 30* is more the norm for the recreational skier.  I don't know.  I decided to go with 45* and see how well it played out on my own skis.

Then I had to figure out a method to determine and measure the Effective Edge at 45*.  I decided to go with two 45* wedge wood blocks.  My blocks are about 3" thick and about 5" tall.  They are positioned on a fairly level flat section of the floor and the ski is positioned on them so that the ski bases rest on the 45* angle of the blocks.  This simulates a ski on edge at 45* that has NOT yet been decambered.  This is key.  I decided not to mess around with decambering skis as that would lead to inconsistent results due to that variance in being able to decamber a ski consistently to the same amount.  I also reasoned that the edges are beginning to engage while the ski is still cambered and as pressure is initially being applied.  So why not just go with the ski in its "natural" form?

So with the ski resting against the wood blocks I once again use that thin business card and slide it between the floor and the ski coming in from the tip and from the tail.  Where the card stops is then marked on the edges of the ski at the tip and tail.  Note that the resulting marks are very different from what you would arrive at in determining CRS.  To measure the Effective Edge length I use a flexible metric tape measure.  I chose to go with flexible tape since it can closely follow the actual edge to determine its length.  A standard metal tape measure would result in measuring the chord length between the marks would introduce some additional error.

With the length of the Effective Edge in hand, the midpoint is easily determined and then marked on the ski.  This is the new spot where we want to position our BoF.  So from this position we measure rearward by the amount of our BoF to Midsole adjustment value.  This position is the new calculated midsole mark to be used when mounting the binding.

Calculating the Ski's Custom Midsole Mark for Binding Mounting:

1. Position the 45* wedge blocks on a fairly flat smooth floor.
2. Strap the ski brake and place the ski against the blocks so that the base is resting against them with the ski sitting at a 45* angle.
3. Make sure that the ski base is consistently in contact with the wedge blocks across the entire face of the blocks (no gaps).
4. Slide a thin business card in from the tip and then mark that position on the ski edge.  Do the same for the tail.
5. Using a flexible tape, measure the length between the tip and tail marks DIRECTLY along the edge.  Do not stretch the tape between the marks (aka chord length).
6. The value obtained in step 5 is the Effective Edge length taken at 45*.  Divide that value in half to find the midpoint and mark it on the ski (this is the CEE)
7. From the CEE mark measure rearward by the amount of your BoF to Midsole Mark adjustment.  Mark this point on the ski.
8. This final mark is your new calculated custom midsole mark that will be used for the binding mount.

Interestingly enough, on "standard" skis, traditional sidecut and camber, the position determined by the new CEE method almost exactly corresponds to the mount position determined using the older BoF over CRS method.

Please note that I strongly believe that this method results in a STARTING POINT for coming up with your ideal mount position.  It is not an absolute.  Only further experimentation will confirm/deny that the BoF over CEE method has provided the best mounting position.  So you may ask yourself why bother at all with all this insanity?  I would say because you have to start somewhere and personally I do not trust the manufacturer's mark as a starting point due to my long history with testing binding mount positions and almost never ending up using the manufacturer's mark.

I will provide additional posts regarding my own skis, where the marks ended up, and how the testing went.  I need to re-energize my batteries before continuing...

karpiel - you're new enough to Epic to have missed all the background on this subject (it goes back quite a few years).   (You're not so new at TGR ).  Many moons ago we had those discussions about the why.  Hit the search engine and dredge up the fodder.  Another good starting point is Lou's Tech Articles.

I know that at TGR it's all about asking each other WTF to mount the bindings on a ski and everyone chimes in on the consensus.  IMO that's crap - what's good for one person isn't necessarily good for another.  I discovered BoF on CRS years ago and had great success with it, but it won't work for the new ski designs so I wanted to develop an updated method that could still provide a high degree of success.  I'm hoping I've got one now.

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Hopefully this will be the last post on the why instead of discussing the method. 

Please let's keep this out of the trash can and not turn it into a religious war about manufacturer's mounting marks.  If anyone wants to go there again then start your own thread and I'll be happy to chime in there.

BTW - I posted this updated method because of a few requests I've received (both in threads and PMs).  So I decided to go ahead and stick it up here.

I'm looking for point and counterpoint on the method to hopefully arrive at something I can trust going forward so I don't "smoke" any of my skis with bad mounts.  My Wailer 112RPs still sit unmounted because I'm not totally committed to this new method yet, but neither do I trust the manufacturer marks since I'm not "average".  The snow is flying in CO and I'm getting really antsy about getting the Wailers mounted. 

     Quote:

Originally Posted by comprex 

All this tells you is that the ski width dimension diferences (tip/waist/tail, i.e. cross-axis dimensions) are very, very small compared to the overall axial running length.

The only way you could get big path differences with such small numbers is if one side of the running surface midpoint were to have a side-cut curve of significantly higher order than the other side.

Sorry, but you lost me.  Care to elaborate in simpler terms that I can understand?

Quote:

Originally Posted by comprex 

What you're trying to find is the center of effective edge (CEE), thus:



and your original observation was that:

Quote:

Originally Posted by Noodler 

Interestingly enough, on "standard" skis, traditional sidecut and camber, the position determined by the new CEE method almost exactly corresponds to the mount position determined using the older BoF over CRS method.

<

and I said

Quote:

All this tells you is that the ski width dimension diferences (tip/waist/tail, i.e. cross-axis dimensions) are very, very small compared to the overall axial running length.

IOW, the reason there is not much difference between point G and point H is because on real skis, unlike the diagram above, the distance BE is so much, much smaller than the overall length CD.




The smaller we make BE relative to CD, the less difference between G and H.

The immediately obvious corrollary is that , for traditional sidecut and camber, shorter skis, (like SL skis frex) will have a greater /chance/ of a difference betweeen G and H.
 

Got it!  And well done may I add.

Quote:

Originally Posted by axebiker 

Too much time and heartache dedicated to this.  Mount 'em, and ride 'em.

I have absolutely no problem with this view.  To each his own.  All I have ever evangelized is that there are multiple options available to us when we mount bindings on skis - not just where the manufacturer says we should mount a binding.  If you care about finding the very best position then you will entertain the idea of following some of this method (if not all of it).  Or you'll be happy with the "luck of the draw" and assume that the ski is fine where you currently are mounted (and it just may be).

Not many skiers have gone to the lengths I have in experimentation with binding mount positions.  I know what the position means to my skiing - sure you can adjust for a mount position in a number of other ways, but personally I don't want to alter my skiing style for a particular mount position.

Just today I was demoing the Blizzard Magnum 8.7 and brought the skis back in and asked the guys to move them 20mm forward.  That change completely improved the edge grip and turn initiation for me.  Such a simple change and yet it results in dramatic differences in performance.
 

Quote:

Originally Posted by Whiteroom 

I have a hypothesis about this method, but need more info.

 

Could you tell us where your method has you placing the binding compared to the manufacturer's line on a few of your skis? I'm really wondering if you are finding you are more often ahead of the line, near the line or behind the line? And by how much? 

 

 

What method are you using to minimize stance differences from ski to ski? Do you use the same binding on everything?

I have a "theory" that I know what your "hypothesis" is.  More than likely it centers around "skier type" and/or technical skills.

Before I post my current quiver data on mount positions I'll answer your last question - almost every ski I own is mounted with Tyrolia bindings and almost all have equivalent deltas.  I'm fairly careful about this variable because I know how the binding delta plays into this equation.

If you'll look at the last column you'll see that positive values indicate a more forward mount than factory and negative values are a more rearward mount than factory.  Note that the values are in cm.  If anyone is interested in a more detailed explanation of this table I'll be happy to provide it.

Cheat sheet: Pub Len = Published Length, CL = Chord Length, RL = Running Length (aka contact length), EE = Effective Edge, TBP = Technical Balance Point (term from Lou), Mid S = Midsole.  Note that there are both Estimated (Est.) and Actual (Act.) measurements included.

And hey, please consider that skiing for me is a hobby.  I tackle this hobby from both the physical/instructional side of skiing and the gear geek side.  I know that not many skiers go to these lengths, but for me it's part of the fun.  I totally understand if this doesn't look like fun for you.

I just realized that I hadn't yet updated my chart for my most recent tests of the Scott Crusade and Palmer P02.  They now also get a bold green font for the "current mount status".  Bold green font indicates that the ski has been tested and that I like the position.

The Scott Crusade has an early rise/early taper tip, dual radius sidecut, and this "venturi" business going on in the tip and tail.  It is not a traditional design.  Had I mounted using BoF over CRS I would have been well behind the factory mark.  The new CEE method resulted in a mount 25mm forward of the factory mark.

The Palmer P02 is similar - not a traditional ski at all - it's a rockered groomer ski.  The factory mount was way forward on the ski and I believe that accounts for some of the reviews that have been posted on this ski.  It actually skis much more like a normal ski when the mount is more "realistic".

Typing this reminded me of another "theory" of mine about a ski's "sweet spot".  There is a similarity between mounting position and the sweet spot on a tennis racquet or a golf club (both other sports I participate in).  Some tennis racquets and golf clubs have different size sweet spots.  The area where you feel like you get a truer hit or strike.  I believe the same can be said about skis.  There are some skis that have larger sweet spots when it comes to binding mount positions.  Even Nordica came out with binding technology (the XBI) that helped skiers stay in the sweet spot even when their fore/aft balance wasn't quite spot on. 

So let's say we have a ski with a sweet spot of about 25mm for your body morphology, binding choice, and skiing style.  As long as you get the mount somewhere within this sweet spot (your BoF lands within this region) you're going to like what the ski does for you.  If the mount was right in middle of the sweet spot then a forward or rearward mount of only 10mm would still have you within the sweet spot.  You might not notice much of a difference.  However, if your new mount position ends up outside of the ski's sweet spot you'll probably hate the ski.  So basically we all know that it's very easy to be too far forward on a ski or too far back.  There's a sweet spot (or should we say "region" in this case) we want to be in.

So what defines the sweet spot is up for discussion.  I would imagine that the ski construction (core profile), sidecut, flex pattern, etc. all play into the location and size of the sweet spot on any given ski.

This is why my actual preference is NOT to go through this method of measurement and analysis.  My preference is actually to have binding systems that allow us to routinely and easily re-position the binding at will (I posted about this last season).  I would much rather take 3 runs with the binding in 3 different positions and pick one.  Seriously.  Unfortunately most of my current bindings don't have this freedom. 

Quote:

Originally Posted by Whiteroom 

A theory is an explanation of 'how' things work, a hypothesis is a guess as to how things may turn out, in say, an experiment. My hypothesis has absolutely nothing to do with skill or skier type. If this works for you that's great, I'm not looking to criticize. I just want to know how your method looks compared to manufacturer's suggested points. That's it.

 

So, on average you end up +1.06cm ahead of the manufacturer's mark, with a big variation on the DPS, Palmer and Stormrider XL. Are you skiing the skis on the recommended point then adjusting to your calculated point, or just drilling them at your point? Once again, I'm curious, I'm not looking to criticize.

 

In the "early days" of my skiing of newer shaped skis (2001-2006) I was always mounting on the factory mark.  I think it was in 2005 when I started experimenting with mount positions.  So much of my experimentation then was with those same skis that had started out mounted at the factory mark. 

More recently (2009-2010, note that I was "sidelined" due to injury from 2007-2009) I have attempted to mount according to BoF over CRS.  I have only very recently begun using BoF over CEE.  I have tested 9 different skis on 15 separate occasions.

The need for BoF over CEE really started to sink in last season when I became increasingly dissatisfied with some of my BoF over CRS mounts.  I ran into problems with my Elan SL Race skis and the Stockli Spirit Pro.  Luckily I could experiment with those due to their binding systems.  This Fall I discovered that my preferred Spirit Pro mount position that I found last season through experimentation landed exactly on the position found through BoF over CEE.  That was one of the situations that started building my faith in this new method.  I have not yet re-tested the Elan SL Race skis (hopefully will happen on Black Friday of this week).

Quote:

Originally Posted by Whiteroom 

Griffon Schitzo, 6cm of adjustment.

Yep, and it's not the only one.  Some manufacturers are "hearing the call" even if they're claiming it's for other reasons.  I really like the new Blizzard IQ system.  Tyrolia has a new system out, the PowerRail, but it's basically a no show in North America this season (except for untracked.com).
 

I should also mention that I have not yet mounted the DPS Wailer 112RP skis.  I'm really on the fence about what to do with those.  The bindings I was going to mount on them leave no room for position adjustments.  I'm hoping to catch a DPS demo day and ride them on the factory mark before making any permanent decisions.  The skis were too expensive to screw this up.  It's either that or go with an adjustable binding (like the Schizo).  Although my BoF over CEE comes up with a +5 mount I was planning on going +3 since they'll generally only be used when we get good dumps.  However, DPS swears that you really want to be on the mark or maybe +1.  It's a real dilemma for me (especially since CO has been getting pounded by big storms).

Quote:

Originally Posted by Whiteroom 

I have some hypothesis' on how rocker effects skis on firmer snow, and why the generic term doesn't describe much. It's based on a 'floating mount point' or 'virtual mount point ' if you will.

I'm all ears - please go on.  Your post about ski construction from a week or two ago was classic and well appreciated.  I know you know your stuff (and it doesn't hurt that I trust your shop too - I've purchased a few pairs of Stocklis from you guys).