The NNN/BC Truth Thread

[anrothar]

I could only find one explanation in a quick search. This guy seems to back up my theory, but two people having the same opinion does not make it a fact.

The NNN NIS bindings rely on two bumpers or “dual flexors” to keep the ski horizontal as yous swing it forward to become your glide ski. Is it as quick as the Pilot? It all comes down to skier feel and expectations.

From: http://skihaussteamboat.com/nordic-cros ... -bindings/

[anrothar]

More from the Rottefella site. The Xcelerator flexors allow you to switch between classic and skate, the quoted text on the previous page was for switching to skate(I think), this was their advice for switching to classic. It sort of explains what the main function of the flexors/bumpers is:

By switching to a softer flex (light grey), the pressure on the front of the ski is reduced which will prevent the skis from digging into loose snow. A hard flex (dark grey) will bring the ski back more quickly after the kick and will also increase pressure exerted on the snow. Suitable for hard packed snow.

So, at least for the Xcelerator bindings, that seems to back up both of our thoughts. That it both increases the speed of the ski swinging forward, off the snow, and also puts more pressure on the snow, increasing grip.

[anrothar]

Seems like a toe bumper of some sort could be added to these AT toe pieces relatively simply to create an AT toe piece with the binding benefits of the nnnbc system.

http://skimo.co/ski-trab-gara-titan

.....IF you could swallow the price....

[Nick BC]

Here's a post from one of our SWBC Canada brethren on his mod. He just did a fairly gnarly and challenging traverse from Blackcomb to Mount Currie on this gear.

http://www.ubc-voc.com/.../going-light- ... cking-with....

[anrothar]

Here's a post from one of our SWBC Canada brethren on his mod. He just did a fairly gnarly and challenging traverse from Blackcomb to Mount Currie on this gear.

http://www.ubc-voc.com/.../going-light- ... cking-with....

The ski crampon mod is awesome! I thought the Rossi bcx9/10 were thermomoldable? My bcx9 and bcx5 were.

Interesting how he's doing the exact opposite of what we ended up going toward here in AK. Nordic bc system bindings and boots on AT racing skis vs AT racing bindings and boots on nordic bc skis.


A note on his binding weights and prices: While the Speed Radical binding is as heavy as he listed for the whole set, he's comparing it to a freeheel setup. Just the Speed Radical toepieces, with bolts and crampon clips, are around 300 grams for the pair and under $200 USD, not sure about the conversion. Compared with the 530 grams for a pair of nnnbc magnums. You can go down to about 175 grams with the Speed Superlight toes at $270 USD.

[MikeK]

I had though that it wouldn't be a stretch to make a block to hold those Xcelerator flexors for an AT binding. Perhaps a good small business idea for someone who has a small mill (hint, hint) Seems like the lock is in the way though on most designs. Perhaps this one might be a good start:



Not sure it would hold you in very well down hills though.

Also had the mad idea of having a removable TTS heel piece so you had all three options: free pivot, flexor pivot, active heel cable.

[lilcliffy]

Free-pivot bindings were created to facilitate climbing- not XC skiing.

The physics of boot-binding resistance is fundamental to Nordic ski technology and technique.

"True" Nordic ski technology requires resistance in the boot sole and/or binding in order to produce downward "kick", so that there is enough grip, to stride forward on the alternate leg (or control the rear ski in a telemark).

Before NNN the resistance came entirely from the boot sole, and with the invention of NN- from the duckbill as well.

The flexors (bumpers) on NNN bindings create resistance- in other words; NNN bindings are not free-pivot.

The physics of this is not different than the resistance in a Telemark binding. With a Telemark binding, heel resistance transfers power downwards into the ski- facilitating a number of effects including the ability to reverse-flex the rear ski, and steer/edge the rear ski.

The resistance of the NNN flexor transfers heel-lift into downward force. In a XC context, the downward force compresses the camber underfoot, facilitating an efficient “kick”. (i.e. the kick is downwards- not backwards. The propulsion of an efficient diagonal stride is the result of grip allowing you to lunge forward on one leg- it is not the product of pushing, or “kicking” backwards).

The Rottefella quote that Anrothar posted confirms this:

By switching to a softer flex (light grey), the pressure on the front of the ski is reduced which will prevent the skis from digging into loose snow. A hard flex (dark grey) will bring the ski back more quickly after the kick and will also increase pressure exerted on the snow. Suitable for hard packed snow.

The other quote is referring specifically to skate or freestyle XC skiing:

The NNN NIS bindings rely on two bumpers or “dual flexors” to keep the ski horizontal as you swing it forward to become your glide ski.

Unlike Classic technique; the glide ski is lifted clear off the snow when skate skiing. Skate bindings typically have a stiffer flexor, not only for reduced heel-lift, and “kick” power- but also to make it easier to keep the glide ski stable (i.e. “horizontal”) when it is carried through the air.

The binding resistance in NN comes from the flex of the boot sole and the duckbill. The stiffer the sole/duckbill flex- the greater the downward power transfer (this is precisely why I personally do not like soft-flexing, floppy 75mm boots in the backcountry).

The NNN flexor brings adjustable resistance right into the binding; and it allows the skier to produce downward kick right out to the end of your foot- the trailing foot provides grip, to allow a very powerful forward lunge. This increased efficiency of the Nordic kick made NNN inherently more efficient than NN.

As a comparison test- try a XC ski with NNN/NNNBC bindings and take the flexor out. You will lose grip at the end your stride, and the free-pivot may cause you to over-extend the trailing foot.

Free-pivot bindings were created to facilitate climbing- not XC skiing.

Now, when xcountry-skiing on an “alpine touring” ski- with little to no camber underfoot- the benefit of binding resistance is much reduced- if not lost entirely.

Anrothar:

As far as I know, in correct k&g technique you engage the wax with a flat foot, and and it stays engaged while your toes are still flat on the ski, once your toes pivot up(and the front of the boot contacts the bumper), your wax pocket is disengaged and that ski moves into the swing-glide phase. The wax engagement is supposed to happen pushing down, not back. By the time your toes contact the bumper, your foot is behind you,

The flexor is engaged as soon as the boot heel begins to lift. This occurs as soon as you swing the glide ski forward. Once the glide ski is ahead of the “kick” ski, the trailing foot cannot possibly remain flat. In fact the longer one's stride the less time your "kick" (the trailing foot) is flat on the ski. Your foot is flat on the lead ski (the glide ski). The advantage of NNN over NN, is that it facilitates the engagement of downward grip right out to your toes.

Bgregoire:

Luc has a lot of sound info relevant to this discussion here:

https://thingstolucat.com/ski-touring-equipment-guide/

I agree with most everything he has to say, especially about the 75mm / NNN/BC bit

Relevant info about those AT boot and bindings too...

There IS a lot of good information in Luc’s post- but IMO, not when it comes to the discussion on NNNBC.

There are of course limitations to any technology. But Luc isn’t discussing the limitations of NNNBC he is simply dismissing it entirely because it does not suit his skiing context. This is worthless and misleading.

There are many, many skiing contexts where I would not choose NNNBC in the backcountry- that doesn’t make it useless as a backcountry binding technology.

In fact, the fundamental reason why I like NNNBC is that it is designed for a very specific backcountry-xcountry skiing context. In short- it is not designed to be “good at everything”. I see that as a good thing.

There is no panacea of Nordic skiing technology.

What I take from Luc and Anrothar’s context is that if you are going to be skiing in conditions where your boots and bindings get wet and freeze- NNNBC ain’t the ticket.

That doesn’t mean that NNNBC isn’t a legitimate long-distance backcountry Nordic binding.

And ignoring the icing-up issue- where is the evidence of all these NNNBC toe bars pulling out?

Back to Mike's question about the resistance of the NNN flexor...

I argue that for efficient true Nordic "kick and glide" performance, there must be some resistance in the boot sole and/or binding. There is this new theory that somehow resistance works against K&G efficiency. This is not true- we are on skis- skis that glide freely. The resistance in the boot-binding does not affect the glide of the ski.

Resistance also affects heel-lift. This has a huge affect on climbing efficiency. A free-pivot binding is vastly more efficient at climbing because there is no resistance to lifting your heel- not because the ski glides more freely.

(Reducing heel-lift is important in skate/freestyle skiing and Nordic skating as well- as the ski/skate is lifted clear off the snow/ice)

At least in xcountry skiing there is a balance that must be struck between resistance and flexibility. If there is too much resistance, there is too little flexibility and the ability to freely stride is reduced. (Johnny posted this winter that he was finding the standard NNNBC flexor too stiff for K&G. This may reflect the type of snow he was skiing on. Perhaps he needs a softer flexor in his particular context?)

One of the advantages of NNNBC versus NN is that the flexor allows you to K&G with quite a stiff-flexing sole. In order to facilitate comfortable, flexible striding, a NN boot must have a relatively soft-flexing sole- which compromises resistance and power.

From my perspective, in the backcountry, if NN is "better" than NNNBC, it is primarily because it is more versatile, allowing the skier to trade up to a much wider range of boot power- from flexible BC-XC, to powerful Telemark.

But if you don't mind having different technology for different skiing contexts- having both NNNBC and NN setups will offer better performance overall.

I have given up on the idea of "quiver-killing" ski technology.

I have embraced the idea of having a range of setups that deliver high performance for a very specific context. As a result- each one of these setups does not deliver optimum performance outside that context.

Just because NNNBC bindings ice up in wet conditions doesn't mean they are worthless as a backcountry-xcountry technology.

Just because my T4s and 3-pin-cable bindings are too restrictive for optimum K&G doesn't mean they are worthless for XCD skiing.

Just because AT tech delivers miserable XC performance- doesn't mean it isn’t worth the sacrifice to be able to climb and ski truly extreme terrain.

[MikeK]

I had hung onto that idea of versatility from the beginning, thinking that keeping one binding system would allow me to mix and match skis and boots freely.

What I found out with my own experience and my wife, there was never a situation where I wanted to use a plastic boot with a really skinny ski. It can be done, but it just didn't appeal to me. My wife tried it but the skis are still hard to turn and kick and glide suffers immensely.

There is also a reason I haven't switched my wider skis over NNN - it's not that I think I couldn't control them with the right boot (I thought that at one time but given the boots I have now, I think that may not be true anymore), it's now rather the fact that I could ski them with a more powerful boot and it would make sense.

My current thought that below a certain width (sidecut really), a stiffer camber and with a longer length, I'd rather have NNN and take advantage of the gliding aspects. I still find these skis adequate to maneuver - not nearly as easy as it would be with a shorter length, lesser camber, more sidecut (and/or rocker) and more boot power, but adequate for overland skiing in many different snows. I'll evaluate wax this coming season and really see if there is an advantage in fresh snow and climbing. In a broken track or hard snow, I have no doubt they will be superior.

As far as the stiff sole - that is an issue. Can be an issue on either system for heel lift. Ideally we want a really torsionally stiff sole with a nice soft toe flex and supportive, but unrestricting upper. Fact is it's hard to make a leather boot, or any boot that does that. Doesn't much matter what the system is.

I think Johnny was confusing some things and I've talked to him about it. His issue with NNN is heel lift. I believe the real issue is boot fit but the fact that he was comparing the NN Alaska to the NNN Alaska and that the NNN Alaska had a much stiffer sole, making the heel lift issue worse.

I told him perhaps to look into an exo-skeleton boot so he would have an instep buckle to pull his heel down into the pocket and hold it tight. He's firmly against the skeletons though... I suggested he make formed heel insert for the boots, a half liner if you will, to help take up the volume. I also saw someone post some aftermarket buckles that perhaps he could add onto the Alaska. There is an internal plastic heel stiffner that could be tied into. I'm not quite sure how you'd keep it waterproof though after riveting the buckles on. Maybe some seam sealer tape on the inside?

[akmtnrunner]

Free-pivot bindings were created to facilitate climbing- not XC skiing.

The physics of boot-binding resistance is fundamental to Nordic ski technology and technique.

"True" Nordic ski technology requires resistance in the boot sole and/or binding in order to produce downward "kick", so that there is enough grip, to stride forward on the alternate leg (or control the rear ski in a telemark).

Before NNN the resistance came entirely from the boot sole, and with the invention of NN- from the duckbill as well.

The flexors (bumpers) on NNN bindings create resistance- in other words; NNN bindings are not free-pivot.

The physics of this is not different than the resistance in a Telemark binding. With a Telemark binding, heel resistance transfers power downwards into the ski- facilitating a number of effects including the ability to reverse-flex the rear ski, and steer/edge the rear ski.

The resistance of the NNN flexor transfers heel-lift into downward force. In a XC context, the downward force compresses the camber underfoot, facilitating an efficient “kick”. (i.e. the kick is downwards- not backwards. The propulsion of an efficient diagonal stride is the result of grip allowing you to lunge forward on one leg- it is not the product of pushing, or “kicking” backwards).

The Rottefella quote that Anrothar posted confirms this:

By switching to a softer flex (light grey), the pressure on the front of the ski is reduced which will prevent the skis from digging into loose snow. A hard flex (dark grey) will bring the ski back more quickly after the kick and will also increase pressure exerted on the snow. Suitable for hard packed snow.

The other quote is referring specifically to skate or freestyle XC skiing:

The NNN NIS bindings rely on two bumpers or “dual flexors” to keep the ski horizontal as you swing it forward to become your glide ski.

Unlike Classic technique; the glide ski is lifted clear off the snow when skate skiing. Skate bindings typically have a stiffer flexor, not only for reduced heel-lift, and “kick” power- but also to make it easier to keep the glide ski stable (i.e. “horizontal”) when it is carried through the air.

The binding resistance in NN comes from the flex of the boot sole and the duckbill. The stiffer the sole/duckbill flex- the greater the downward power transfer (this is precisely why I personally do not like soft-flexing, floppy 75mm boots in the backcountry).

The NNN flexor brings adjustable resistance right into the binding; and it allows the skier to produce downward kick right out to the end of your foot- the trailing foot provides grip, to allow a very powerful forward lunge. This increased efficiency of the Nordic kick made NNN inherently more efficient than NN.

As a comparison test- try a XC ski with NNN/NNNBC bindings and take the flexor out. You will lose grip at the end your stride, and the free-pivot may cause you to over-extend the trailing foot.

Free-pivot bindings were created to facilitate climbing- not XC skiing.

Now, when xcountry-skiing on an “alpine touring” ski- with little to no camber underfoot- the benefit of binding resistance is much reduced- if not lost entirely.

Anrothar:

As far as I know, in correct k&g technique you engage the wax with a flat foot, and and it stays engaged while your toes are still flat on the ski, once your toes pivot up(and the front of the boot contacts the bumper), your wax pocket is disengaged and that ski moves into the swing-glide phase. The wax engagement is supposed to happen pushing down, not back. By the time your toes contact the bumper, your foot is behind you,

The flexor is engaged as soon as the boot heel begins to lift. This occurs as soon as you swing the glide ski forward. Once the glide ski is ahead of the “kick” ski, the trailing foot cannot possibly remain flat. In fact the longer one's stride the less time your "kick" (the trailing foot) is flat on the ski. Your foot is flat on the lead ski (the glide ski). The advantage of NNN over NN, is that it facilitates the engagement of downward grip right out to your toes.

I know this is an old thread, but in case someone comes across it in a search (as I did), I'd like to respectfully disagree with Lilcliffy in regards to the bumper (or flexor) increasing grip. Hear me out.

A nordic boot flexes easily at the ball of the foot, without influence on the binding. This is the key difference to a tele boot, which has either a cable around the heel or stiff bellows to transfer torque via a heel lift. In order for a nordic boot to exhibit the torque into the binding/ski, the top-front of the boot must move forward into it, which means rotation about the binding pin, which means the ball of the foot has risen away from the binding/ski.

This is not to say that we don't press downward with toes to contribute into the kick, just that the vast majority of our kick happens while the balls of our feet are still also pressing downward into the ski. Our toes just aren't equiped to be powerful enough to carry the full force to flatten the ski camber by themselves. I also hope to not marginalize the instrumental role of the toes. Only they can fine-tune our balance on the ski, to guide our body's powerful kick in just the right way.

The cited response from Rottefella doesn't contradict this, nor Anrothar's assertions (which I agree with). I am certain Rottefella's references of the bumper's influence on ski pressure are not during the kicking phase, but during the return phase, when the ski is unweighted. Having that downward tip pressure is instrumental during the return phase to steer the ski straight before it is weighted. A softer bumper is appropriate in softer snow, a stiffer bumper in firmer snow, because the required pressure to edge into those snow surfaces. Again, just as Anrothar has described.

I've nordic skis many times without bumpers, as they fall out easily from my favorite old pair of skis. By far, the only significant effect is loss of control while the ski is unweighted. Now, I will say that that loss of control translates into a loss of confidence in that ski as I approach the unweighted phase . . . at the end of the kick Confidence in controlling the ski self-governs our effort. And if our effort (force) wanes at the end of the kick, there's less pressure flattening the camber, meaning less grip. So I can completely understand someone would conclude that a free-pivoting binding means less grip. I contend though, that it is not for the reason they may think it so, and only as significant as they believe