Unusual But Important — Dynafit Breakage

Yesterday, Colin Samuels sent me a message and photos from France, about a mode of Dynafit breakage he experienced. He’s recently been publishing about this elsewhere, and it seemed appropriate to get a discussion going here at WildSnow since we’ve got somewhat unique insight into the whole Dynafit spectrum.

From my own experience I can say this form of breakage is extremely rare (I’ve actually seen it before, but only on bindings with so much use they should have been in the scrap heap). Nonetheless, even if this has only happened a few times on fresh bindings, anyone with moderately heavy use on their Dynafit bindings should be inspecting the toe base metal structure for cracks. As Colin relates in his take (below), such cracks might not be obvious. I’m thinking the best way to test for cracks might be to do a sort of release bench check with the boot in the binding. Or, perhaps good lighting and a magnifying glass would be the way to examine the binding.

Also, I’m thinking that it might be smart for those of you using FT with big boots and big skis to install the Dynafit Power Plate, since it provides more support at the outside edge of the binding base. Again, I’d repeat that this failure mode is rare, but at the same time if it does happen it is very catastrophic (sort of the ultimate pre-release), so I feel it’s our responsibility to get this out there for you guys.

Dynafit FT breakage, click image to enlarge.

Dynafit FT breakage, click to enlarge.

Colin’s own take included quite a bit of conjecture as to causality and possible consequences, but I think he’s worth reading. He published over at TGR, I repeat the same thing below. I’ll publish everything Colin wrote, but remember to separate fact (the binding broke) from theory (why it happened, or what Dynafit is doing or should be doing about it.)

Another thing that occurs to me is that the base of the FT binding toe is actually NARROWER than that of the ST. I always found that to be strange. It is possible that the small amount of difference could allow just enough flex in the binding base for metal fatigue to take place (regardless of what kind of “Torsion Plate” or whatever the binding base is ostensibly trying to be.).

Of interest to me and perhaps to some of you long time WildSnow readers, you might remember that some time ago we conjectured about how the newer generations of Dynafit bindings would hold up to being used basically as alpine bindings, since they were originally designed without that purpose in mind. It’s indeed been amazing how well the binding has evolved to a grabber that can support big skiers, boots and skis. But it’s still built to be LIGHT, so the engineering challenge of keeping it durable is quite difficult.

In Colin’s take he talks quite a bit about the “Torsion Bridge” having some causality in this. Could be, but I’d say it’s more likely metal fatigue caused by big boots and skis working the binding base plate in an area where it doesn’t have much direct support down on the ski. Or, perhaps that’s what Colin means? For the record, I publish Colin’s take below:

I am 6’2″, 185lbs on Factor Boots and Megawatt skis 2008 model (white). The bindings that failed were FT 92mm binding (re-fitted with 110mm breaks), Din 12 and purchased in France on March 2010. The bindings were mounted with a jig by a Dynafit certified technician on a new pair of skis. The bindings had roughly 30 days of use before failure occurred. The heels were set at 12, a turn left from maximum. The toes were locked.

I had experienced a toe pre-release one and two days prior in totally different situations – one just after the first turn off the lift and the second on a high speed ride through a low-angle field of broken-crud studded with hard snow chunks. I felt right away that both of these pre-releases were strange, as I have been skiing Dynafits for ten years with no previous problems in similar conditions. I checked the toes for cracks and verified that there was no ice under the boot or in the toe piece among possible causes.

It is my guess that the toe piece plate was already cracked and weakened, but not completely sheared yet, as seen in photo. But I did not know this at the time as the crack must have been hidden from view.

On the third day, during a traverse on soft snow at medium to high speed, the binding suddenly released at the toe for no reason and the ski shot out from under me. I made a controlled fall and discovered the toe piece had failed. I was lucky not to have hit a tree or rock.
If the failure had happened earlier in the run, there is a good chance I would not be alive to tell this story.

Cause of failure appears to be from two different reasons:

1- The newly designed torsion-bridge under the FT Toe Piece creates a “lever effect” which I believed caused the failure by adding additional stress just under the screws, as seen in the photo. The ST and TLT models for example do not have the torsion-bridge and their toe plates are a lot wider and thus give a wider distribution of force around the toe piece screws.

2- The exposed metal of the broken toe piece exposes white looking spots in the metal itself which begs the question as to Dynafit’s quality control and quality of the metal itself.

Conclusion: The FT series torsion-bridge causes additional torsion to the toe plate screws which can result in unpredictable pre-releases and/or complete failure in the form of shearing of the metal toe plate around the screws.

Serious injury or Death can result from such an unpredictable failure.
There is no doubt that the new torsion-bridge can not handle mixed/hard
conditions under higher speeds when skied with a combination of a 4 buckle Freeride type-boot (e.g.Factor) and fat skis 110mm underfoot or greater (125mm under foot in my case).

Thus, the FT is simply overwhelmed at the toe piece because of the poorly designed FT torsion-bridge.

Dynafit, in their description of the FT on their website states:

The patented mechanical four-point link between binding and boot, along with the intricate torsion-bridge between toe and heel, provides a previously unknown degree of force distribution to the ski.

Ironically, it is my belief that the torsion-bridge actually creates additional weakness to the toe piece by increasing torsion directly under and around the toe-plate screws, especially when used with fat skis. Also, it may be possible that there was a quality issue with the metal used. However, upon receipt of the broken binding, Dynafit never requested a serial # for the binding which leads me to believe that they were not concerned about faulty metal/poor quality control.

However, it is possible as well that the metal used in the toe-piece is of inferior quality and this is also what added to the failure, or was possibly the principle cause.This would require a detailed study, which Dynafit has not undertaken to my knowledge.

Incidentally, last winter here at the same ski area, another Dynafit FT failed exactly at the same place in the toe piece through sheering; the skier was of similar build, with a similar fat ski/stiff boot combo.

After 10 years of skiing 500 plus days on Dynafits I have never experienced any serious problems of this nature. I have not only skied many rare steep descents with Dynafits, but I have convinced many friends to trust their lives with the Dynafit binding system.

Now, I have serious and well-founded doubts that the Dynafit binding system, FT 12 or others, can safely handle the additional torsion and power created by the modern Freeride Boot/Fat Ski combo when skied aggressively in mixed conditions and terrain.

I warn all Dynafit users to seriously consider the consequences of a failure as described and documented here.

I will continue to use my Dynafits (without the torsion-bridge of course!) but I refuse to use FT’s or other Dynafit models for lift-accessed freeriding involving high speeds and high torsional forces in mixed snow conditions.

Please spread the word about this failure of the FT, and the risk it poses.

I believe Dynafit has known about this problem since 2010 and that they have kept such failures quiet as they hurriedly designed a new toe piece/ torsion-bridge to prevent future failures as I have described here. It will be interesting to know if anyone else has experienced similar failure with FT torsion-bridges.

Hopefully Dynafit will both warn its customers of potential and sudden failure of its FT Binding series, as well as make the needed improvements to avoid any future failures. If not, I sadly predict serious injuries/fatalities in the near future among Dynafit users, especially those with FT torsion-bridges.

Sincerely
Colin SAMUELS
La Meije, France
January 21st, 2011

Dynafit FT toe wing overhang. Truly surprising this would hang MORE than ST model. I'd been aware of this for a long time, never saw any failures so thought it was a non-issue. I was wrong. Click image to enlarge.

Dynafit ST overhang, significantly less than current FT model. Rather surprising, but perhaps that's why I've always felt ST was perfectly fine for nearly anyone. Sure, it doesn't go to eleven, but most people don't want to rip their foot off their leg if they fall, so good.

Another photo from Colin.

Radical ST for 2011/12, no overhang. All other Dynafit models for 2011/12 are similar in that none have any overhang of the toe wings.