Binding Mount Position Tolerances and Effect

[karlo]

That's not hard to do at all with simple shop tools. You can use a Vernier Caliper if you have one, or go low tech and just use two carpenter squares, some painter's tape, a metric ruler and pencil. Mind you, you will only be as precise as you have the ability to be with either high or low tech tools, so if you don't have an engineer's mind and/or a mechanic's feel then, buyer beware, or in this case user beware.

Low tech method: ( assumes a "flat" ski, not a system rail mount )

Note: This is the center width line running longitudinally, not cord center line, and not of the entire ski length, just the binding mount area. Let's assume you are using a paper binding template and want to center it before you drill. You will need to find the center line of the ski at each ends of the template to line up the center line of the template to the center of the ski. You could also use this center line to verify that a mount jig is centered. This assumes you've already figured out the boot center mark and binding center marks. That's another task not covered here. We are only covering the ski center line longitudinally.

First off, ignore the top sheet and any marks on it because top sheet marks may not be correct (we can debate how that happens during manufacturing elsewhere). Your goal is to find the center of the ski, based on the width at two exact fore/aft locations, at the ski's base, metal edge to metal edge, and transfer that to the top sheet. You are interested in the width of the ski at the surface that interacts with the snow, not the top of the ski. Yes the center should be the same top and bottom regardless, but as they say: shite happens and this will verify it if nothing else.

Find two spots on the ski, one just fore and one just aft of your binding template extreme ends. Note: the width of the ski will be different at any given location along the ski length. Place a piece of painters tape across the the top sheet of the ski at the template extreme locations. Let's start at the fore (towards tip) location. At your painters tape fore location put a carpenter's square body flush along the bottom of the ski and the square's tongue against the metal edge. Make sure the square is not cocked sideways and is as perpendicular to the ski edge as you can make it. Place another carpenter's square opposite the other on the other side of the ski. Again, make sure everything is flush and not askew. You can now simple measure the distance at that exact top sheet location between the two tongues of the two carpenter's squares using a good metric ruler and mark the center of that measurement on the painter's tape affixed to your top sheet. Repeat at aft ( towards tail) location. Now you have two center marks on the top sheet (based off the ski's base width) on the painter's tape at these two extreme binding end locations. Take a straight edge and draw a line between those two center marks longitudinally. Be mindful of the pencil line width. Now you have a center line of the ski within the range of the binding. Again, this a low tech method. Anyone can do this with enough care and some simple tools they probably already have around the house.

Edit to add: Oh darn I got side tracked. I wanted to add the reason you need to measure the base width edge to edge and then transfer that to the top sheet is that measuring the top shoulder edge of the ski is problematic, esp. with cap ski construction. Jigs essentially do this.

So, if i want to more than eyeball it, I need to be sure that the center of the already-mounted toe piece, both fore and aft, match the center of the ski. And, same for heel. Right?

 

[karlo]

I skied them for the first time today. Heavy snow fall previous day and overnight. The result was heavy compacted snow. It was very easy to initiate the turn starting at the tip. So, that’s good. But the ski was so reactive, I felt like I was on a pinwheel turn to turn. Is that what happens when a binding is mounted forward as little as 5-mm? What if I mount it back a bit, to the line?

This is a 171 85-waisted 22-radius ski. I don’t think it should be a pinwheel, should it?

 

[GregK]

I skied them for the first time today. Heavy snow fall previous day and overnight. The result was heavy compacted snow. It was very easy to initiate the turn starting at the tip. So, that’s good. But the ski was so reactive, I felt like I was on a pinwheel turn to turn. Is that what happens when a binding is mounted forward as little as 5-mm? What if I mount it back a bit, to the line?

This is a 171 85-waisted 22-radius ski. I don’t think it should be a pinwheel, should it?

As many of us mentioned, the tune or base flatness will be far more noticeable than a very small movement forward. Your bases are probably not flat and sound base high. Will be super easy to pivot and turn but feel unstable or like marbles under your feet on certain snow types. Poor edge grip on harder snow too.
A stone grind to flatten the base and then touch up the edges and you’ll be good!

 

[karlo]

the tune or base flatness will be far more noticeable

I checked with a straightedge. Perfectly flat at tips, mid and tails. New skis, first day on them, so it’s a factory tune. I always like Blizzard’s factory tune. Must be the ski. I’ll see as the week goes on how I feel about them in other conditions.

 

[GregK]

I checked with a straightedge. Perfectly flat at tips, mid and tails. New skis, first day on them, so it’s a factory tune. I always like Blizzard’s factory tune. Must be the ski. I’ll see as the week goes on how I feel about them in other conditions.

My blizzard Rustlers needed 2 separate grinds till they were decently flat and my last 30 pairs of skis from several companies were not flat from the factory and all needed grinds to flatten before hand setting the edges. My brand new Dynastar skis are edge high and would be harder to turn and wanting to go straight, so the opposite of yours it sounds like. Mine will be going in for a grind and I’ll tune them before they touch the snow.

If they seem off, they probably are and it’s not the mount position that’s the issue. Sometimes it’s hard to see the see tuning issues at first that show up when skiing but trust your instincts.
I’d have a shop check the bases and edges if they still seem “off” after skiing them more. Base high skis will seem more more unstable in variable conditions.

 

[dovski]

So here is a binding mount question for the thread. We bought my daughter a new pair of boots over the summer because her feet just won't stop growing, and low and behold all those attempts to slow her growth seem to have paid off as the boots are now a size to big for her, so moving on to plan be a smaller pair of boots, the thing is her Head Kore 87 JR (162 CM) skis were just mounted for the larger boots with a 305 BSL and the boots she will end up using have a 295 BSL. We can properly adjust the forward pressure on her bindings (Marker Squire) but effectively this becomes a 5 mm forward mount. Is this likely to have any impact on her skiing? Curious as what the wise folks on this thread think

 

[EricG]

I skied them for the first time today. Heavy snow fall previous day and overnight. The result was heavy compacted snow. It was very easy to initiate the turn starting at the tip. So, that’s good. But the ski was so reactive, I felt like I was on a pinwheel turn to turn. Is that what happens when a binding is mounted forward as little as 5-mm? What if I mount it back a bit, to the line?

This is a 171 85-waisted 22-radius ski. I don’t think it should be a pinwheel, should it?

karlo - Dont take this the wrong way. But I wonder if your head is playing games with you since you know they are mounted a few mm forward? It’s making you overthink things versus just enjoying the day on snow.

 

[markojp]

So here is a binding mount question for the thread. We bought my daughter a new pair of boots over the summer because her feet just won't stop growing, and low and behold all those attempts to slow her growth seem to have paid off as the boots are now a size to big for her, so moving on to plan be a smaller pair of boots, the thing is her Head Kore 87 JR (162 CM) skis were just mounted for the larger boots with a 305 BSL and the boots she will end up using have a 295 BSL. We can properly adjust the forward pressure on her bindings (Marker Squire) but effectively this becomes a 5 mm forward mount. Is this likely to have any impact on her skiing? Curious as what the wise folks on this thread think

No.

 

[Ross Biff]

So here is a binding mount question for the thread. We bought my daughter a new pair of boots over the summer because her feet just won't stop growing, and low and behold all those attempts to slow her growth seem to have paid off as the boots are now a size to big for her, so moving on to plan be a smaller pair of boots, the thing is her Head Kore 87 JR (162 CM) skis were just mounted for the larger boots with a 305 BSL and the boots she will end up using have a 295 BSL. We can properly adjust the forward pressure on her bindings (Marker Squire) but effectively this becomes a 5 mm forward mount. Is this likely to have any impact on her skiing? Curious as what the wise folks on this thread think

This is an interesting point. Let's just assume for the moment that the manufacturers marked mount point is in the correct position and we mount using the mount point mark on the boot. A binding mounted for a 25 mondo boot- let's say bsl 295, compared to a binding mounted for a 29 mondo boot with a much longer bsl would result in the ball of the foot pressuring a different part of the sidecut of the ski. I guess this is were alternative mounting methods using boot sole toe as a starting reference point come into play. Still....if we then get the forefoot in a more advantageous position, a longer bsl may place the rear of the foot in a less advantageous position. Sounds messy I know but as has been noted previously, a bad tune will have a greater impact and most competent skiers can more readily adapt to different mount points than a base high or edge high ski.

 

[Tony S]

More important is centered and not skewed.

Yah.

I bought skis from someone on this board (or Epic). They arrived and you could see the crooked mount from ten feet away. (Toes close to one edge, heels close to the other edge.) Had to send the guy pics with measurements, which of course bummed him out. He was nice and took them back with no problem, but it's not how he imagined things working out.

 

[GregK]

So here is a binding mount question for the thread. We bought my daughter a new pair of boots over the summer because her feet just won't stop growing, and low and behold all those attempts to slow her growth seem to have paid off as the boots are now a size to big for her, so moving on to plan be a smaller pair of boots, the thing is her Head Kore 87 JR (162 CM) skis were just mounted for the larger boots with a 305 BSL and the boots she will end up using have a 295 BSL. We can properly adjust the forward pressure on her bindings (Marker Squire) but effectively this becomes a 5 mm forward mount. Is this likely to have any impact on her skiing? Curious as what the wise folks on this thread think

Will be a far greater difference with the proper fitting boots than a slight movement forward which might be actually beneficial to the ease of turn initiation.

My latest skis have a mounting range of 6cm between the “park/freestyle” and the “all mountain” marks and most ski designers say you can easily stray plus/minus 2cm from rec mounting points without issue. So a plus or back 5mm is a non issue and other factors will be at play if the skis feel off.
A movement 1-2cm will be noticeable but more a slight flavoring of traits -“more playful/ski shorter/easier to start turns” with a move forward and “more stable/skis longer/better float/more powerful carving” with a move back.

And about 99% of the time if skis “feel off” after skiing them a reasonable time to get used to them, there probably is something off with the tune, ramp on the binding etc.
The other 1% might be in your head from overthinking mount points....

 

[Doug Briggs]

Everyone should realize that lots of race skis come with pre-drilled plates. They are spaced 1 cm. So racers, unless their techs remount their plates, can be 5mm off of their boot center mark using the nearest set of holes to there BSL.

Of course it can be less than that, but I haven't had a single racer ask for a remount due to the 'fixed' location of the holes on the ski.

Blind testing of placement of bindings could go a long way to alleviate much of the stress factor in 'is my binding mounted in the right location' and 'does 5mm make a big difference'.

Please, no one be offended, but concern over 5mm is 'paralysis by over-analysis'. As has been mentioned tune and snow conditions play a far greater role in a skis performance than 5mm in binding placement.

 

[Noodler]

Everyone should realize that lots of race skis come with pre-drilled plates. They are spaced 1 cm. So racers, unless their techs remount their plates, can be 5mm off of their boot center mark using the nearest set of holes to there BSL.

Of course it can be less than that, but I haven't had a single racer ask for a remount due to the 'fixed' location of the holes on the ski.

Blind testing of placement of bindings could go a long way to alleviate much of the stress factor in 'is my binding mounted in the right location' and 'does 5mm make a big difference'.

Please, no one be offended, but concern over 5mm is 'paralysis by over-analysis'. As has been mentioned tune and snow conditions play a far greater role in a skis performance than 5mm in binding placement.

But... you could be in a situation where that 5mm of change puts you outside of the good "sweet spot" on the ski for you. IOW, normally 5mm isn't that noticeable, but if you were already on the very edge of what's acceptable/necessary, then that 5mm is going to have more impact. In that situation, I would recommend going back in the other direction (if you're dealing with a fixed plate set of holes).

So to the OP question, I would say 10mm; yes, definitely, but 5mm maybe, sometimes.

I have found that shops generally have more trouble with "skewed" binding mounts than an incorrect fore/aft position. The jigs do wear out (making them less accurate) and it's also easy to not notice if the jig isn't sitting perfectly flat. In that situation, the holes end up skewed toward one side of the ski.

 

[Noodler]

That's not hard to do at all with simple shop tools. You can use a Vernier Caliper if you have one, or go low tech and just use two carpenter squares, some painter's tape, a metric ruler and pencil. Mind you, you will only be as precise as you have the ability to be with either high or low tech tools, so if you don't have an engineer's mind and/or a mechanic's feel then, buyer beware, or in this case user beware.

Low tech method: ( assumes a "flat" ski, not a system rail mount )

Note: This is the center width line running longitudinally, not cord center line, and not of the entire ski length, just the binding mount area. Let's assume you are using a paper binding template and want to center it before you drill. You will need to find the center line of the ski at each ends of the template to line up the center line of the template to the center of the ski. You could also use this center line to verify that a mount jig is centered. This assumes you've already figured out the boot center mark and binding center marks. That's another task not covered here. We are only covering the ski center line longitudinally.

First off, ignore the top sheet and any marks on it because top sheet marks may not be correct (we can debate how that happens during manufacturing elsewhere). Your goal is to find the center of the ski, based on the width at two exact fore/aft locations, at the ski's base, metal edge to metal edge, and transfer that to the top sheet. You are interested in the width of the ski at the surface that interacts with the snow, not the top of the ski. Yes the center should be the same top and bottom regardless, but as they say: shite happens and this will verify it if nothing else.

Find two spots on the ski, one just fore and one just aft of your binding template extreme ends. Note: the width of the ski will be different at any given location along the ski length. Place a piece of painters tape across the the top sheet of the ski at the template extreme locations. Let's start at the fore (towards tip) location. At your painters tape fore location put a carpenter's square body flush along the bottom of the ski and the square's tongue against the metal edge. Make sure the square is not cocked sideways and is as perpendicular to the ski edge as you can make it. Place another carpenter's square opposite the other on the other side of the ski. Again, make sure everything is flush and not askew. You can now simple measure the distance at that exact top sheet location between the two tongues of the two carpenter's squares using a good metric ruler and mark the center of that measurement on the painter's tape affixed to your top sheet. Repeat at aft ( towards tail) location. Now you have two center marks on the top sheet (based off the ski's base width) on the painter's tape at these two extreme binding end locations. Take a straight edge and draw a line between those two center marks longitudinally. Be mindful of the pencil line width. Now you have a center line of the ski within the range of the binding. Again, this a low tech method. Anyone can do this with enough care and some simple tools they probably already have around the house.

Edit to add: Oh darn I got side tracked. I wanted to add the reason you need to measure the base width edge to edge and then transfer that to the top sheet is that measuring the top shoulder edge of the ski is problematic, esp. with cap ski construction. Jigs essentially do this.

An easier way to find the center line is to use a triangle, not a square. I have a triangle with a wide flange positioned so that is aligned with the ski side edge. The way this works is to put a reference point on the ski top and use that point to align the triangle at the same position for both sides of the ski. You then use the 45* angle of the triangle to pencil a line diagonally across the ski surface. When both lines are drawn (one from each edge), they will intersect at a point in the exact middle of the ski. Do this a couple more times down the length of the ski and then use a long straight edge to create a line down the center through the points made using the triangle. You'll get a perfect center line every time without the need to measure anything.

 

[karlo]

karlo - Dont take this the wrong way. But I wonder if your head is playing games with you since you know they are mounted a few mm forward? It’s making you overthink things versus just enjoying the day on snow.

Please, no one be offended, but concern over 5mm is 'paralysis by over-analysis'

I would say 10mm; yes, definitely, but 5mm maybe, sometimes

Skied them a second day. This time, steeper terrain, softer powder. I think these may simply not be the skis for me