Summer Technical Geek Discussion #1 - Ski Binding Position

A snowHead

Disclaimer – This is meant to be a highly anal discussion of where to mount your ski bindings and hopefully will get your techy ski brain cells working during the off season. Open you mind and contribute if you find this topic interesting, take the p1*s if you like but us geeks will just ignore you. Toofy Grin

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So…. I got myself a pair of factory SL skis and it has gotten me thinking about correct position of the boot along the length of the ski. There are a few threads on this which are very good and there seems to be three methods quoted to determine the "correct" position to mount your bindings. But how much difference does it really make to your skiing and what method is the way to go.…

There seems to be three popular methods for determining binding position on Alpine Skis.

Campbell Balancer Point (CBP) - basically a wobble board that you stand on the find your balance point. The figure quoted is the distance from the front edge of the boot back to the contact/running length centre line of the ski measured in cm’s. This method is individual to your physiology, boot set up and stance and should be quite accurate.

Ball of Foot over Centre of Running Surface (CRS/BoF) you can determine where your ball of boot is within your boot by several methods and then position this point directly over the CRS as measured for your skis.

Centre point of Boot over Manufacturers (BM) mounting point. This is the default setting used by manufacturers and shop technicians. Occasionally you will get a ski marked with two marks, a "FreeRide" or "FreeStyle" point. FreeRide tends to be further back to allow for off piste skiing keeping your tips higher, and FS is more forward and is meant to assist when doing aerial manoeuvres & rail grinds and is meant to indicate teh cmetre of the skis mass to help keep the skis more balanced rotationally.

For me both CBP and CRS/BoF methods came out the same figures and are typically around4 cm forward of BM method of manufacturer recommended binding position marked on all my skis. Both on and off piste I prefer the more forward setting. This could be unique to me because I have big feet but 4 cm seems to be a lot and it has been reported elsewhere that most competent skiers when balanced end up with a more forward “prescription” than what BM point would suggest.

My “new” SL skis are second hand FIS factory race skis and bought off a sponsored racer who competes at international level. His binding location was set individually for him at the manufacturer’s factory by their top technicians and I was told that they initially set the centre point of the ski boot which is marked on all boots directly over the “middle flex point” of the ski. The technicians measure this point at the factory and is dependent not only on the design of the ski model but is unique to each individual skis stiffness pattern. When I determined where my bindings should be overlaying my boot to his I found this put my boot even more forward (2 – 3cm) than what the CRS/BoF point would indicate. which for me already tends to give quite a forward mounting location.

It just looked Waaayyy too forward and as I had to redrill the mounting plates to fit my boot length I wanted to think this through and ensure I wasn’t missing something. I began wondering if this ultra forward mounting point was only for good racers and would be impossible for an average skier like me to get on with. So I asked another ex sponsored racer, who knows how to ski, about this and he had an interesting view on the matter….

The Bof/CRS is old school and was fine when we needed to project forward along the ski and used more rotary input to steer the skis. With modern skis with large sidecut radii we steer more with pressure and edge. We get higher edge angles and higher loadings by standing more on top of the ski as opposed to moving for and aft, or, twisting the feet. When aggressively skiing you will generate several G’s of force through your body down through your skis to the engaged edge. This force should go through the load bearing part of your foot, which is NOT the ball of the foot, but the “keystone” point along your arch known as the Navicular point. I believe that it is this point that the boot manufacturers typically stamp on the boots and should be aligned with the “Middle Flex Point” of the ski.

The actual flex point centre not necessarily the centre of running surface but is very much dependent on how the ski is constructed and the “sweet spot” location is dependent on the stiffness and flex pattern for that model of ski. Shorter SL skis with stiff tails it is more critical to align the flex point of the ski to the point on your foot that the force vector is transmitted through.

I find all of this interesting in an Academic way and it raises a few Questions. I would be interested in getting views of people in the know.

Does anyone know if the Centre Point marked on boots by manufacturers is actually meant to represent the centre of the arch or is it just an arbitrary position each boot manufacturer uses? Are there any industry standards?

Is the manufacturers mark on a ski related at all to the designed flex pattern?

Should binding mounting point be determined by intended usage as opposed to skill level?

Manufacturers literature tend to say that “expert” binding position is further back and “recreational” position is forward to “ease turn initiation” It seems to me that this is opposite to what I have found and that a more forward position is suitable for all skiers who will be on piste on in the park and further back for off piste in soft snow. The Free Ride, Free Style markings make sense to me and should they add an on piste only or Race mark?

Is there any point in using a campbell balancer as opposed to BoF/CRS?

Does a skiers weight have any bearing on binding position?

It is probably impossible for users to determine the flex point of a ski but should SL skis be mounted typically further forward than BoF/CRS would indicate?

A snowHead

skimottaret, Why not go with BM and see how they ski ? All my race skis are mounted that way.

Boot fit may play a part too, the marking on real race skis may presume that the BoF is further forward in race boots than it would be in a recreational boot.

You can find out with a tape measure whether the centre point is really in the middle, it is for both pairs of boots I have here.

Well, the person's real but it's just a made up name, see?

I have no idea in answer to your questions. I'd have thought for a pure SL ski that will not be seeing the soft stuff you can mount as far forward as you like as keeping tips up won't be an issue although maybe you miss out on harnessing some of the power in the tail if you go too far.

I do know on some of my older skis how I'm amazed at he shortness of tail relative to tip from the manufacurers marks and know I know more I'd be inclined to mount them forward of the line. I think I need to do some measuring of where my current skis are mounted on effective edge to get an appreciation for future mounts as I like the position on them.

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skimottaret, based on your large boot size, the toe of boot will be infront of the centre of the ski.... the manufacturers boot centre mark is often set up around a boot 300-310mm long typically if you measure back 15cm from the centre of the running surface you will line up with their mark...as you boot is 305+ Xmm you will likely find that this 4cm plus measurement you like to the toe of the boot puts your boot centre somewhere around the boot mid point mark on the ski

does that make sense???

there are a lot of other things whihc i think are a lot more important in the whole chain but it is a consideration

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rjs, the race skis i have dont seem to have a centre point mark on the top sheet, my newer ones had a mark scribed on using permanent marker. what that mark actually represents is not clear. I have also heard from Spyderjon that the centre marks the manufacturers ink jet print on are nowhere near repeatable from ski to ski and that one should measure CRS for a reliable datum point.

CEM, what do the manufacturers of skis typically consider as the Centre? is it CRS, chord centre, point of min sidecut, the nominal flex point i mention, or something else?

Interesting comment regarding boot size vs centre point (for reference i am a 334mm length) are you saying that the boot centre marks (BCM) are positioned for a single "reference" size? i would have assumed that each size of mould would have a centre point that relates to the actual boot length and position of foot within the boot.

Do you feel the Boot centre Mark should be at the navicular point? or was that idle speculation by my friend..

comprex, fair points... i guess the balancer is probably better as it considers lean and ramp angles, beer guts, stance etc.... It may have been just coincidental that my CB and Bof/CRS points coincided. The CRS seems to bear little similarity to the ski manufacturers mid point. As there is only one balancer in the UK that i am aware of i was hoping to get a more generic set of figures that relate to measurable info like CRS, boot centre point etc. and apply that to type of skis (SL, GS, off piste , all round etc) For instance i am guessing SL skis will like more forward mounting point as opposed to DH skis...

I am assuming that each manufacturer does something slightly different, this is skiing why have standards wink

but it would be good to know if i can correlate something that i can measure when setting binding locations on differing skis or when giving advice.

i should rephrase the weight question as if i am much heavier than an "average" skier should i typically go forward or aft with my bindings?

Then you can post your own questions or snow reports...

skimottaret, on a ski whith no visible centre boot mark [it happens a lot] we used to measure the tip to tail in three ways...tip to tail along the base, tip to tail along the top sheet and chord length....add the three together, divide by three and divide again by 2 which gives an accurate chord centre, this would be consided the boot toe or dependant on the skier measure 15cm back and use as the boot centre point

i have never really thought about the boot centre point being under the navicular, it is half way along the lenght of the boot...does that correspond with the navicular???? not really though about it

After all it is free

CEM, Thanks for the Chord Centre measuring method.

Not wanting to get silly but rather would like to come up with some simple methods that i can use to determine where I should mount my bindings. Manufacturers use a "standard human model" method that doesnt work for us on the fringes. wink

A cm or two isnt going to make much difference on a pair of soft recreational skis but for stiff race skis i would think the "sweet spot" is pretty small and binding location is much more critical. +- 3 or 4 cm will make a huge difference in how a race ski behaves.

There is a lot of information on binding mounting for telemark skis but very little for alpine so i am trying to summarise a few methods for people to use as a starting point. Personal preference and intended usage then comes into play but if i took a pair of skis which dont have a mounting point mark on them to a "ski technician" what method would they use to determine where they are going to drill holes in my skis?

there a few methods and each seems to have pros/cons and give different results. I will write up my thoughts along with some guidelines on how binding position affects ski performance and publish them here for review. Perhaps armed with some information people can make a more informed choice when having bindings installed.

skimottaret, What is the difference between your BSL and that of their previous owner (AT ?) ?

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rjs, previous owner is smaller stature and feet (good guess it was AT) . I think his boot was around the 300 mark but not exactly sure.

Have to admit i am not sure i correctly follow CEM's thinking on boots bigger or smaller that industry average. Lets say i am 30mm longer than average. should i go back a full 30 or half the distance? I would think half would make more sense in relation to the boot centre line.

i didnt want to drill the skis and remount the plate and was able to use some of the existing helicoils and then drill and helicoil the plate to give me two positions to play with. The 1st one i mounted the bindings to keep my boot centre mark directly over his point and the second 1 cm aft of this to allow for my bigger feet. I currently have them forward and two goes in the dome and hey are very hooky and i have been spat out a few times.

Interestingly if i use my Campbell balance point over the CRS i am 2 cm forward of current position. So if i take it back a 1 cm notch almost bang on the CBP/CRS that i like to use

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skimottaret, I think moving back by half the difference in size.

One other variable would be how tight a fit your boots are, any extra space will be at the toe which will move your foot back relative to the centre line. Moving the bindings back by 1cm sounds about right to me.

snow reports

rjs, yeah half makes sense to me as well. fair point on boot tightness but that is accounted for if you use a campbell balancer or just tap test to find your Ball of Foot within your shell.

the thing that sparked this off for me was that i now have two pairs of FIS race skis that are virtually identical in dimensions. The old pair (Fischer RC4's) are retail models with the bindings pre positioned, the Blizzards were set up at the factory. when i put them side by side the the RC4s are 3.5 cm aft of the blizzards. even going back a cm to get em back to a bit, 2.5 cm difference seems a lot to me and sparked this off.

I am concluding that CBP/CRS is the one for one piste usage and should get you close to optimal before adjusting for personal preferences.

God this is so geeky it is making me excited. Love this guys brilliant discussion and made me think about stuff that would normally never enter my head!

You know it makes sense.

Otherwise you'll just go on seeing the one name:

fatbob, why would a pure SL ski not see the soft stuff? Isn't that what they were designed for?

A snowHead

under a new name, The new Fischer WC SLs don't work very well in powder, it all goes through the hole in the tip.

A snowHead

comprex,

Well, the person's real but it's just a made up name, see?

skimottaret, All my race skis are mounted using the centre mark over mounting point and ski just fine using 225mm and 235mm boots.

You described your new ones as "hooky", are you sure you are not just noticing the difference of a real race tune ? You want them to carve arc to arc.

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think about the COM change when you add or remove a spoiler from the boot, or make the cuff more upright, or lift the heel internally or externally or lift the toe of the boot externally, whilst the campbell balance point is relevent as you say for your boot set up as it is on the machine any one of the changes listed although small can make a dramatic difference to the COM

this is one of the areas which is in the equipment awareness modual which we are trying to get introduced

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Then you can post your own questions or snow reports...

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skimottaret, My previous post was wrong, my boots are 325mm and 335mm.

skimottaret, lever lengths are interesting things , on an average leg length (greater for you as you are so tall) 1degree of adjustment at the foot =10mm of motion at the knee!!!!!!! this applies in terms of medial/lateral shift, fore/aft it will be slightly decreased as the tip point is much longer (the sole length of the boot), but it is a major consideration

the neutaliser machine that Andi uses also relys on feel and visual, it feels better to you, it looks better too, there is no fixed point everyone is different

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rjs, okay so same as me then. What i dont get is what the manufacturers mark is meant to represent...

CEM, Yes indeed I can see that Forward Lean is a very major issue when trying to get alignment done. probably overrides a lot of adjustment you can do and get that wrong when selecting a boot you are going to struggle to achieve good balance for an athlete.

Pressing you a bit though, After i was balanced and fit by you guys i then got my Campbell point measured by Jon. It was roughly at the BoF point. I appreciate that everyone has different physiology but if you could build a boot for an athlete and had infinite adjustment over forward lean etc where would you want his balance point to ideally be along the sole of his boot?

I would think mid point would allow him most flexibility when piloting the skis but does that ignore gait mechanics and should you be more nearer the Bof when skiing....

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I would aim for between BOF and centre arch....being so tall you will automatically end up further forward than someone with the same set up and shorter legs

try jamming a couple fo hotel rook key cards betwen the sole fo your boot and the AFD at the toe of the binding (SKI CAUTIOUSLY...DO NOT TRY THIS AT HOME IT IS AN EXPERIMENT ETC ETC ETC) have a few runs gently and see how it feels if it feels better then put a permanent lifter on the boot or under the binding ...you could also try putting a lifter under your boot and going back on the balancer...see where that puts you

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Okay to get even more geeky I found some more links which tie up with what CEM said that the Ideal balance point should be behind Ball of Foot. and between this and the centre of arch. This seems to be due to several reasons:

1) the foot having three main points of contact, Ball, Heel and little toe metatarsal and when skiing you dont want to be any further forward than the ball of foot as you will feel like you are going over the handle bars. The little toe is behind the ball so brings the point back.

2)virtually all ski boots have an internal ramp angle and the Heel is always higher than the toe, this is typically 3 degrees but varies by manufacturer. so if you are in "high heels" the balance point will want to be a bit further back.

As a rough guide if you take the distance between your navicular point and the ball of foot and go back 1/3 the difference you get a good "idealized" balance point.

So where do you position this point on the ski? Which method will get you the closest so that you can then adjust for personal preference.?

You know it makes sense.

I must admit I find this all a bit confusing as I have only ever mounted bindings according to the mark on the skis and boots.

I understand the idea of playing with formulae and settings to get the best for yourself.

I have always thought that how things "feel" to the individual is very important. So rather than try and "calculate" the best position to mount the boots why not find some rental bindings that allow a good amount of front and rear binding adjustment. Play with different settings till you find your favourite spot on the ski then leave the bindings in that position or mark the position and drill for other bindings?

Not the geeky submission of other SnowHeads but just a thought to get the "right" placement for an individual.

Otherwise you'll just go on seeing the one name:

fred, that might work fine for you but if you are really short/tall have big/small feet and are outside the statistically average human model the manufacturers setting might not be appropriate and actually hinder your skiing. Also not all skis have marks on them so you have to work it out for yourself.

The manufacturer setting is almost always further back on the ski making them skid more. Studies have shown more advanced skiers generally prefer a more forward mounting point to the Manufacturers settings.

The point of this is to try to get as close as possible before playing around with feel and personal preference. Few bindings have more than 1-2 cm of adjustment, if any, so getting close is important so you dont find yourself having to turn your skis into swiss cheese by drilling holes all over them.

Your idea of playing with some rental skis to see if a more forward or aft mounting point suits your style is a good idea. You could then mount your own skis X cm plus or minus the manufacturers point. But..... each manufacturer of ski uses different rules of thumb to position their marks and the marks themselves arent applied very accurately....

A snowHead

Yea - I agree with what you have said - but I was suggesting rental bindings on your skis not rental skis. That way you only have to drill once for the rentals then once for your own bindings. Only two sets of holes - not Swiss Cheese.

It was just a suggestion and I fully understand that you are into all the tech stuff and formulae as this thread clearly shows. I wish you luck with your quest.

A snowHead

fred, probalem with most demo/rental bindings is that they are A: heavy, B: do not go above DIN 10, C have a higher amount of delta angle than most retail bindings

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fred, sorry, i thought your idea is a good one and i understood that you advocated using a seperate set of rentals to play around with before drilling on your own skis. snowHead

As a general rule of thumb it would work quite well.

An excellent idea if you could test position using adjustable rental bindings on the type of skis you own or are thinking of buying so the shop can drill your own skis to suit your needs. Toofy Grin

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comprex, Not sure i am trying to find a park and ride spot, at the end of the day the bindings cant move and your looking for a good compromise.

You are one of, if not the, most knowledgeable equipment guy here with a big quiver of skis. How do you like to position your bindings? Do you use any standard method or just rely on manufacturers points and or shop technicians?

Which factors are the most important? flex pattern, longitudinal stiffness, waist point, CRS, Chord length etc. etc........

I agree that there is loads to consider but at the end of the day you gotta drill some holes in your brand new skis to suit your own physiology, the ski your on, what you want to do with that ski and account for personal preferences. Having a reliable datum point that is transferable between ski models and manufacturers can only help IMO.

The quest continues Toofy Grin

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Did a little more digging and came up with some interesting (to me at least as Head Geek ) info which seems to tie up with what comprex was alluding to. (my guess is that he has already worked all of this out some time ago Toofy Grin

)

As a general rule of thumb Ski Manufacturers design skis so that the ball of the foot goes at the CRS and the mid point line of the boot goes to the waist point. This places 55% of the skis running surface in front of the BCM. This rule of thumb only works for those with average sized feet

What this does in effect is to put the mid sole point of the boot directly over the centre of the side cut radius so when pressuring/edging the ski the force vector is through the middle of the boot. The balance point you use to pilot the skis (your CBP or point roughly just behind your BoF) is more forward at the Centre of Running Surface to assist in steering.

The Industry standard average sized boot (Mondo 27.5 or size 9 1/2 USA 8 ½ UK mens) is approx 300-310mm overall shell length. If your feet are very big, you should therefore move your boot FORWARD not aft along the ski to account for the additional distance between navicular and BoF....

Then you can post your own questions or snow reports...

I think i have figured this all out now and have come up with a new method for mounting Alpine ski bindings which is more robust than any of the current methods.

i have one or two question marks over my theory so if anyone fancies a geek ski discussion on saturday i am all ears.
Toofy Grin

After all it is free

skimottaret, hate to point this out mate, but you appear to be having a discussion with yourself here wink

skimottaret, tell me it doesn't involve No More Nails.... Smile

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FlyingStantoni, i know i seem to be getting lost in the mist of geekery... I have passed my paper on for review to one unnamed snowhead but since your not as geeky as i thought you were (Mr. hard vs soft Ptex) may reserve showing you the light of my invention... NehNeh

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Summer Technical Geek Discussion #1 - Ski Binding Position

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