I had an interesting chat with Harald Harb at short turns camp regarding binding mount position. I was already leaning in this "new" direction, but HH has absolutely confirmed my current thoughts on the correct mount position. I started out using the BoF over center of running length and that evolved to the BoF over center of effective edge, but I started realizing that the point I was finding to work really well for me also corresponded to have the boot midsole aligned with narrowest point on the sidecut of a ski. Without any real "prompting", HH said that this was also his experience and he explained that when you think about what happens when a ski is flexed into an arc, having the boot midsole at the narrowest point is the only mounting position that really makes the most sense. So I have gone back through most of my skis to double-check where my boot midsole sits in relation to the narrowest point of the sidecut and amazingly they almost all are dead on.
I'm going a bit further now, with the hypothesis that when your BoF lands on the center of effective edge AND the midsole mark on the boot also lands exactly on the narrowest point of the sidecut, magic happens. The skis that I own that match this criteria are the ones that I feel are completely dialed in for me. This clearly plays into the ski design arena and I wonder how many ski builders are aware of this relationship when designing the ski geometry.
Last Edit: Nov 6, 2013 1:14:59 GMT -7 by JimRatliff
HA - you make a distinction between BoF/CRS and BoF/effective edge. What's the difference? I have never heard of a reference to effective edge. Furthermore, how are you determining the narrowest point in the sidecut? Seems to me that there might be a significant portion (couple of centimeters at least) of the ski that would measure almost the same dimension using an ordinary ruler, at least with my middle-aged eyes squinting at the little marks. Do you use a micrometer?
Last Edit: Nov 6, 2013 1:15:48 GMT -7 by JimRatliff
Svend - thanks for the interest and here's more detail on the subject since Lynn has so nicely broken this out into its own topic.
For years and years (long before we had factory mounting marks on skis and boots), skiers used the Ball of Foot (BoF) positioned on the Center of Running Surface (CRS, aka midpoint of the running length) when mounting their bindings. Even after we got the factory mount mark on skis and the boot midsole mark, some skiers still preferred to go with BoF on CRS. Of course this was before ski sidecut geometries and tip/tail profiles got, let's say, "interesting". With dual sidecuts, early rise tips, and full-on rockered 5-point designs, BoF on CRS no longer produced the desired results (since determining CRS becomes quite problematic). There has also been some confusion/controversy over how to properly determine where the BoF point really is on your foot and where that point is positioned inside the boot shell. For the purpose of this post it's not necessary for me to get into the details of those issues.
So BoF over CRS evolved into BoF over CEE (Center of Effective Edge). The Effective Edge length is the distance from the widest point of the tip to the widest point of the tail. What makes CEE slightly tougher to determine is that it's the length "along" the edge, not the chord length between the two widest points. IOW, you need to use a flexible tape measure to really do this right; to determine the midpoint between the widest points of the tip and tail.
Unfortunately even BoF over CEE fails with some of the more modern takes on ski design. Some builders do some strange things with the positioning of the ski sidecut and also their new takes on ski rocker profiles. That's where simplifying the whole process by just aligning the boot midsole mark over the narrowest point of the sidecut makes a lot of sense. For this to really work well though, I would recommend that you have a fairly close fitting boot so that the midsole mark on the boot actually corresponds to the midsole point of your foot.
The best method I've found so far to determine the narrowest "point" on a ski's sidecut is to use a digital caliper. Use the caliper to find the approximate narrowest point along the sidecut and then lock the caliper's measurement adjustment (usually there's a thumb screw to lock the jaws in place). The narrowest waist measurement will sometimes occur over a "range" in the middle of the ski; possibly for 2cm or more. This can be handled by taking the locked calipers and marking the forward and rearward points where the locked calipers "catch" on the ski (slide the calipers through the narrow range and mark the forward and rearward points). With those points marked, measure and find the midway point between them and mark that point as the narrowest point of the sidecut (basically it's the middle of the narrowest range of the waist found). The main problem with this method is keeping the calipers square to the center line of the ski while taking the measurements. I'm still working on a type of jig that can make this process faster and more accurate.
Last Edit: Nov 6, 2013 1:17:13 GMT -7 by JimRatliff
Hmmmm....very interesting subject. For years I used to do the BoF/CRS thing on all of my family's skis, and then found that on some skis this just didn't create a sense of a balanced stance. Either the tails were washing out, or one would have to get way forward to get the tips under control and to engage. So I have almost abandoned this method due to too many instances where it simply didn't work -- my wife's im78's, her Progressor 8's, my Progressor 9's.... The final straw came when skiing the Stormriders last spring -- as mentioned, the shop set them up for my friend at the BoF/CRS mark (Knee binding, flat mounted), and it was simply a terrible spot to mount them - felt like it was about 2 cm back of where it should have been.** The shop owner, who is one of the boot fitters on Epic, has long been a vocal proponent of this method, and was punting it to my friend as the magic spot on the ski and the only way to find a mount location. So much for that theory. They were almost unskiable.
This is no big deal for skis with adjustable bindings or plates, as I have simply moved the binding until the skier feels centered and balanced, and the tips or tails are well weighted and under control. But for skis that are flat mounted this is a real dilemma. I have been at a loss to find another method to find a balanced stance, as I am understandably reluctant to go back to the shop for repeated re-drilling. Both of our daughters have twin tips that are flat mounted, as are my wife's Dynastar all mtn. skis, and I guess I have been lucky that the BoF/CRS seems to have worked well for them - the skis handle well, with no apparent issues - but they are all traditional camber and sidecut geometry. However, our youngest is nearing the point when she will have outgrown her Fischer twins and will be ready for a longer ski. Those that I have been checking out for her all have at least early rise, if not some tail rocker too, and I didn't know where to start trying to find a good mounting mark on those, so I had been planning on getting a plate or rail type binding.
Skier stance likely plays a role in this too, I would imagine. My wife, for example, has as her natural stance a rather forward, low and aggressive position, brought about by years of power skating since childhood. Our daughters, OTOH, are much more upright, albeit still driving the shovels with shin to boot tongue pressure. But their fore-aft weight balance is clearly going to be different over the skis. In your experience, does this have any influence on where your final mounting mark settles? Have you set up skis in this way for others, or just your own? In other words, have you mounted according to measurements, only to find that it didn't work for a particular person because of stance peculiarities?
Overall, though, your description of CEE and narrowest sidecut point are extremely interesting. Encouraging, too, that I now have a real alternative to finding the correct mounting point on a rockered and/or multi-sidecut ski, leaving the option of a flat mounted binding still open. You've piqued my curiosity, and I am going to do some measurements of our own skis to see how they line up. My P-9's would be a good candidate, and my wife's iM78's. I don't have a digital caliper, but I do have a micrometer that might serve for now. Re. midsole mark on the boots, I'm not sure if your criteria for a tight fore-aft shell fit is the same as ours, but all our boots are 1/2" to 3/4" gap at heel, toes touching, on a footbed. Hopefully that matches well to the mid-foot spot.
Thanks, H-A. Great post.
**Correction: I just re-read my own review of the Stockli's, and found a note that, while the bindings were indeed set up at the BoF/CRS mark, there was also a riser plate of 8 to 10 millimeters thickness placed under the toe piece, but not under the heel. This would doubtless have influenced my impression of the bindings being mounted too far back.
Last Edit: Nov 6, 2013 1:18:23 GMT -7 by JimRatliff
Jim - I have long trumpeted the fact that skiers with different BSLs would end up in different positions of their BoF over the ski if they all mounted at the factory mark. This was especially an issue for women (and guys with small feet) since their BoF would be much farther rearward.
But here's where things get interesting (and I need more data) - many ski manufacturers do NOT put their factory mark at the narrowest point of the ski sidecut. When they don't it's almost always rearward by a large margin. I believe that HH's point was that it isn't about the positioning of the BoF any longer (not in modern skiing style), but more about being centered over the narrowest point of the sidecut. I didn't get into exactly why this is important previously, but I'll lay it out now. Pretend you have a machine that can bend a ski into a complete arc while stationary on the snow. While the ski is bent deeply, place your ski boot on it at your chosen mount position. If this position is forward of the center of the bent arc then the mere act of bending a ski will put you in the back seat. Can you see why? Because the toe will be more "up" and the heel will be more "down" into the center of that arc. By the same token, a rearward point will have the toe down and the heel up which obviously wouldn't necessarily put you in the back seat, but it certainly wouldn't be in balance against the arc of the bent ski. So the idea is that a bent ski will have the deepest point of the arc (the apex) at the narrowest point of its sidecut when skied on hard snow. Now clearly, many skiers never really bend their skis much at all so the degree of the effect of this situation will vary with the skill level of the skier. The corollary to this is make sure that you can actually bend your skis at the speeds you typically ski. If the ski isn't really getting bent in a turn then you're really not taking advantage of the design of a ski to make it turn.
Another point, consider the design of women's skis. Manufacturers should be doing a lot more than just making them softer/lighter and changing where they print the mounting line on it. They should be adjusting the sidecut position relative to the Center of Effective Edge. That means that they should not just be putting pretty colors and chick-inspired graphics on the same ski that's in the men's line. They should really be developing the skis differently from the ground up to work better for lighter skiers with smaller feet so that the sidecut and the ski profile mesh well for a smaller skier.
Last Edit: Nov 6, 2013 1:19:41 GMT -7 by JimRatliff
HA, really great info and thoughts on the subject.
Interesting theory on women's skis too.
I wonder if the combo of the mounting point and demo bindings results in the foot pain I experience when I demo most skis.
Bottom of my foot begins to scream after a run or two. I demo'ed some ?blossoms? with vist bindings 2 years ago at the North East PMTS meet up and was in near agony. Had to get them off. Not an isolated experience.
Your thoughts on women ski production sounds like an idea whose time has come. Some savvy entrepreneur should take up that as their marketing strategy! Women skis made for real women skiers; not just another pretty ski.
Jim has some bindings to check out this weekend
Last Edit: Nov 6, 2013 1:21:28 GMT -7 by JimRatliff
Are there any new developments to this topic? It's been about a year since the original discussion. Has anyone done further testing or experimenting and learned anything noteworthy to share?
The reason for the question is that I have purchased a new pair of Watea 88's for my daughter, and now need to figure out the binding mount position (I intend to flat-mount, so want to get it right the first time). They have a slight early rise tip, and are also a unisex model, so the factory mark will not be useable.
FWIW, I have had mixed results with the BoF/CRS method, and that on non-rockered skis. It's been a good starting point, but on several of our skis I have ended up deviating forward or back from this mark to end up with a balanced position.
Post by HighAngles on Nov 25, 2013 11:56:20 GMT -7
In an ideal world, one where the ski you're mounting has a fairly even flex, the tip or tail isn't overly stiff and out of "balance" with the rest of the ski", then my current line of thought is to go with planting the midsole of your foot over the narrowest point of the waist (which should also correspond to the thickest part of the ski profile). Of course the midsole of your foot will only be aligned with the midsole of your boot shell if you have a fairly tight shell fit. If your fit is more "relaxed" then your actual midsole is most likely a bit rearward of the marked midsole on the boot (when your foot is buckled down tightly into the shell).
I'm finding that manufacturers sometimes put their factory marks at this point, but not always. So it's worth checking to see how the factory mark actually lines up with the sidecut of the ski and its profile.
At this point, the days of using BoF over CRS are long past when dealing with modern ski designs. The best bet is to experiment with an adjustable binding and for me my starting point is now driven by the sidecut design of the ski, not by any of the contact measurements (whether that's Center of Running Surface or Effective Edge). I know some of you will note this is a fairly major shift in my thinking as compared to years past. What can I say, I'm ever evolving in my understanding of the sport and from my own personal experiences.
Last Edit: Nov 25, 2013 11:57:04 GMT -7 by HighAngles
At this point, the days of using BoF over CRS are long past when dealing with modern ski designs. The best bet is to experiment with an adjustable binding....
I agree. Even with non-rockered skis, the BoF/CRS thing was kind of hit and miss. Worked for some skis and skiers, but not others. Much of the time I ended up moving the bindings either forward or back, which tells me that there was no consistently predictable error involved (ie. BoF/CRS was not consistently 1 cm fwd. or back). Rocker / early rise just makes this even more complicated.
As you say, and based on my own experience, I will likely be going with adjustable bindings from now on, even with wider skis. Either a rail-type, or a light plate.
Good tip on setting a starting point at narrowest part of the sidecut. I will try that and see how it works out. There are two new skis here that need bindings -- Head Mya 9 (Rock 'n Roll), and Watea 88 -- both for female skiers. If that binding point works out for them, I will report back and let you know.
livingproof: Philly is an ice rink this morning, freezing rain over very cold streets. Weather is putting a dent into my ski season.
Jan 5, 2014 9:39:28 GMT -7
Deleted: LP - we had a three-day ice storm here just before Christmas, so I know well what you're dealing with. Not fun. Hope there's no damage in Philly. Take care.
Jan 5, 2014 20:23:02 GMT -7
livingproof: Philly weather warm fog last night, 8 inches of new snow = history! 8 degrees F tomorrow morning. Should be some great local boilerplate!
Jan 6, 2014 7:42:34 GMT -7
meput: - 22° F the other morning. +54° today. Forcast 0° tonight. Temperature rollercoaster at my home. The 'loaf got RAIN with the warm up. Looking forward to skiing on shaved ice
Jan 6, 2014 16:28:43 GMT -7
Deleted: Same story here...25 cm snow last night, some more freezing rain, and now there's 80 km/hr winds and -25 C temps. Wind chill is pushing -40 C. Supposed to continue all day tomorrow too. Whacky weather.
Jan 6, 2014 20:52:30 GMT -7
ToddW: -20° F on the drive up to VT on Friday. Freezing rain and heavy fog Sunday night made for an 8 hour return trip. Record low at home this morning. 40s and rain by Friday. What's up with the weather?
Jan 7, 2014 18:04:52 GMT -7
Deleted: Polar vortex is back. -26 C this morning. Will need a block heater in the car if this keeps up. Poor thing barely cranked this morning.
Jan 22, 2014 7:30:05 GMT -7
JimRatliff: Polar Vortex??? Is that the new Head all-mountain carving ski I've been hearing so much about?
Jan 22, 2014 9:04:03 GMT -7
JimRatliff: That's pretty chilly. 7F (-13C) in Central Park. Glad you didn't send the real cold air down.
Jan 22, 2014 9:04:58 GMT -7
JimRatliff: OK, but I still think "Polar Vortex" and "Polar Express" could be the start of a great family of ski names.
Jan 22, 2014 10:45:22 GMT -7
Deleted: I like it! Blizzard should take those on. Fits with their name. Easier to say than "Viva Ultrasonic Full Suspension IQ", or some such ridiculousness. Who can remember all that?
Jan 22, 2014 20:29:13 GMT -7
livingproof: Another round of Philly area snow....we're ground zero this season. Please start sending any future storms north.
Mar 2, 2014 8:15:55 GMT -7
Deleted: Neverending winter here in Ontario. More snow last night. Cold temps coming this week. Word on the street is that some local ski hills may be open until May. Remarkable and unprecedented.
Mar 22, 2014 9:03:22 GMT -7
superbman: we were supposed to make it to next weekend, but they put out that we're closing tomorrow. Bummer.
Mar 28, 2014 9:06:50 GMT -7
JimRatliff: I think most local places here are closing as well. Yesterday was last at Elk.
Mar 30, 2014 4:17:15 GMT -7
livingproof: My Blue Mtn home is planning to open next weekend (closed midweek). Spring temps are finally here, not sure if I'll make a final trip.
Mar 30, 2014 6:00:04 GMT -7
ToddW: Surefire way to scare away family skiers, from the Killington conditions page: "Expect huge bumps on Superstar for the Killington Triathlon."
May 2, 2014 13:22:58 GMT -7
JimRatliff: I just wanted to wish all a Happy Holidays. Amazing how quickly Christmas follows Thanksgiving.
Dec 13, 2014 14:53:23 GMT -7
superbman: I was looking at the reviews on real skiers for the Kastle FX 85 and FX 85HP…both interested me greatly, how similar are these to the FX 84 (if you have skied both..or is the 85 the 84??)
Sept 13, 2015 14:52:00 GMT -7