UKH

I've experienced some pre-release when executing jump turns on ~45degree terrain while using dynafit st rotation 10 bindings. One popular hack seems to be "locking out" the toepiece to prevent this.

Is anyone aware whether dynafit bindings have a DIN rating for when the toe is locked (in tour mode), or would it only "release" when it fails through force? I believe in ski mode it has a fixed rating of 5. 

Interested to hear others' approach to this.

Cheers

I know 2 people who have suffered broken ankles by doing this. Both forgot to reset to "ski mode" after a steep section, then fell on easy terrain. That said, I did it myself last Sunday despite trusting my Dynafit Speed Turn bindings 100%...never had pre-release. The terrain was steep and scary and I needed the psychological edge that locking them out afforded me. But then, like my 2 mates, I forgot to reset the lever to ski mode after the steep section and then skied the most dire breakable crust for the next 30 mins where just one teak would probably have left me with a nasty injury...

So my understanding is that if they're locked out they just don't release in any practical sense (i.e. before your leg's busted). But am also interested in others experience of pre-release.

I've heard a figure of DIN 25 quoted for older models locked out!

Is your pre-release related to the toe? I had a few pre-releases last week basically while just standing up and turning to face a different direction. The forward pressure screw on the heel piece had moved due to vibration. Loctite fixed that. Worth checking out the heel? 

I echo your comments about forgetting to unlock them. I've often skied in the trees having forgotten to unlock.

Yes, well aware of that danger. I figure if its a toss up between tumbling down a cliff band due to unintentional release, or at least the chance of skiing it with both skis intact, I'll take the latter!

Out of interest which bindings do you have? The toepiece of the rotation ST's actually have 15degrees of rotation, but obviously only when in ski mode.

I haven't lost a ski while charging on a piste - only when doing jump turns.

No, I've had problems with the heel releasing. Good advice re. heel positioning though. Just had a look, and there does seem to be a larger gap than normal between the boot and mech. Cheers!

@davehk - my knees are definitely not 25 din! 

I had a similar problem with my first Dynafit / boot combo and eventually concluded it was the boots, rather than the bindings that were the main problem.  I also skied around with the toes locked on and was told they'd release at something like DIN 16 but I never tested that properly.  The problem happened with Scarpa Spirit 4s but disappeared when I changed to a Dynafit boot, hence my conclusion that the boots weren't ideally suited to the bindings (which were Vertical STs, I think.)

After changing the boot brand (now using La Sportiva) I've very rarely experienced pre-release and the potential consequences of either the pre-release or locking the toes and then forgetting to return to normal make it worth considering a boot change if nothing else works.

There are a couple of operational points that might be worth looking at.  Apologies if this is old hat but someone reading this might find them useful.

The first one is that the holes in your boots where the toe pins engage can be partially blocked with ice.  I don't think that this is very common but Dynafit do build in a fix for it.  If you look carefully at the toe pins you can see a small groove in each one.  The idea is that when you click into the toe, but before engaging the heel pins, you pick up your foot and put it down a couple of times.  That causes the pins to rotate relative to the boot and the edges of the grooves grind out any ice.  I've also seen some people carry a small proddler made from coat hanger wire to clean out the holes before going downhill.

The second one (and I think this is much more common) is a build-up of compacted snow or ice under the articulated bar that links the posts that hold the front pins.  The bar has a fulcrum halfway across that clicks downwards when you push down with your toe and the space underneath it has to be clear for the pins to move to the fully-in position.  (Hopefully this is making sense - it's a lot easier with the binding in front of you.)  Again, some people make a point of cleaning that space out after skinning but my personal hack is to glue a piece of closed-cell foam in there so there's no room for snow to build up in.  The binding just compresses the foam out of the way when you click your toe in.

Hope that helps!

Ah - just seen you post about the heel being the problem.  The older bindings used to be set up with a gap of about 5 mm between the heel piece and the back of the boot - there was a little plastic spacer for this in the box when you bought new bindings.  I'm told that the newer ones are set up with a smaller gap so it might be worth some investigation on exactly what that's supposed to be for your bindings.

useful source here for information regarding heel gaps on bindings

https://skimo.co/tech-binding-heel-gaps

Thanks! I had no idea that ice could become blocked under the toepiece, but makes sense. Will be adopting your solution. 

Having done some research - my binding isn't listed above - the gap is actually way smaller that I originally thought.

Cool!  That's very handy.  Thanks.

Glad to help! Maybe klep an eye on it. I noticed my gap was incorrect after a ski fell off just after the top of a lift. I adjusted it back there and then, and carried on skiing. An hour or so later it happened again. I'm not sure if it was the ice corduroy, or vibration on the lift, but it kept working itself loose. Never happened before. Over a few hours of skinning and powder skiing, it didn't budge at all. I've put some loctite on the relevant bit and it's been fine since. It was fine for several years before that too... Odd. Definitely made the binding pre-release though.

Edit - mine need the 5mm gap, so may not be relevant to yours if they have a smaller gap.