Side vs underfoot tension

[Mattaboy]

the Voile transit binding coming out is exciting. It’s the best uphill weight I’ve seen on a tele binding, and it gives me hope that tele gear will be roughly on par with AT within my lifetime.

the cable routing got me thinking though.

I’ve had boot out problems on piste before with the switchback x2. It might fine on a blue, but it feels a bit sus in the backcountry.
I didn’t stick with the switchback so I want to ask the crowd:

side vs underfoot tension routing

do folks find boot-out with side cables to be a problem? How did you overcome it, or did you?
Does Routing cables underfoot like the BD-01 solve the issue?
Does the side cable improve lateral control, or is it just a patent infringement thing?

[jtb]

Side vs. underfoot routing doesn't affect the tension of the heel throw on the boot. There shouldn't be any impact on boot retention or lateral control. The exception would be something like the Bishop BMFR or Spike binding, where there is additional hardware besides the spring providing lateral stability. But if we're comparing between Hardwire/BD01/Vice, they would all have similar properties for boot retention, given similar spring tension.

The problems with putting springs on the side of the boot are:

• limits spring length and width; pretty much restricted to what's offered by Voile or Kreuzspitze
• limits activity setting; if you want very low activity, you may get interference between the boot and rods or springs unless you mount them very wide

Mounting springs under the boot solves the above problems but introduces some new ones:

• underfoot hardware causes snow packing issues, especially when touring
• more complicated linkage to the boot heel increases complexity, weight, and height off the ski

My experience has been that the limits of the spring become more of an issue at the resort, because the skier tends to apply more leverage on hard pack, moguls, and tracked up crud, thereby needing stiffer and/or longer-travel springs to avoid bottoming out and bending hardware (or worse). This is why you tend to see underfoot springs on resort-focused bindings. The lightness, simplicity, and lack of snow packing with side-mounted springs is a big win in the backcountry, where the power limitations on the spring are not as much of a drawback as at the resort.

TL;DR: if you're booting out of Hardwire springs, you need stiffer springs and/or increased preload on the boot. My guess is you're not booting out of Voile stiff springs at high preload. The factors going into how the springs are routed are more relevant to the forces and travel you need for the type of skiing you do, and not boot retention or lateral control.

[bobbytooslow]

the limits of the spring become more of an issue at the resort, because the skier tends to apply more leverage on hard pack, moguls, and tracked up crud, thereby needing stiffer and/or longer-travel springs to avoid bottoming out and bending hardware (or worse). This is why you tend to see underfoot springs on resort-focused bindings. The lightness, simplicity, and lack of snow packing with side-mounted springs is a big win in the backcountry, where the power limitations on the spring are not as much of a drawback as at the resort.

Hadn't thought of it in these terms before, but this is absolutely correct. My resort skis have mostly underfoot springs (22D Vice), and my touring skis have side cartridges (Voile LT).

I'll add that the bigger stiffer boots used at the resort will generally not shorten as much when flexing (compared to a softer touring-minded boot), and so they'll require more spring travel to allow the knee to get low without the springs bottoming out. And it's tough to fit a spring with that much travel into a side cartridge.

[jasonq]

i'll add another downside to side mounted springs, you can knock the cables off with the other ski. This can actually happen with any heel throw type configuration, just easier with side springs.

to convince yourself of this, put a boot in a binding with a heel throw. now press down on the wire/bail/whatever that leads to the heel throw. The throw will rotate down and snap off. it is surprising how easy this is to do if you can step down on it with your opposite ski. it takes a good deal of preload to minimize this, but i am not convinced preload can totally eliminate it. And of coarse preload makes a binding more active, and also reduces usable spring travel. So not a free lunch.

side springs just give a nice big target to press down on. And the wire bail coming out the back is generally centered on the spring, which is farther from the boot, creating another bigger target.

i personally think like 50% of pre releases attributed to low preload are actually this and not low preload.

the solution is to use a leash that attaches to the top of the throw and prevents it from rotating back off. BTS and myself have post pics of these types of leashes before.

[Charley White]

I think the bootout mattaboy is referring to is not boot leaving binding but boot\binding contacting hard snow at a high edge angle and losing edge purchase. As in why WC racers had such high shims. (Or like "pegging it" on your motorcycle.)

[jtb]

I think the bootout mattaboy is referring to is not boot leaving binding but boot\binding contacting hard snow at a high edge angle and losing edge purchase. As in why WC racers had such high shims. (Or like "pegging it" on your motorcycle.)

Ooh, good point. I hadn't thought of this problem in a long time. I think TTS mitigates it by placing the pivot block under the foot, and putting the heel throw higher on the boot. This may be a 75mm problem, as that's the only binding where it's possible to have the boot flat on the ski.

[cesare]

I read that the same way as Charley White. I was going to ask OP how wide are your skis? NTN bindings do not have wings as wide as SBs so unless the ski is quite narrow, I wouldn't expect any boot-out, if that's what you are talking about.

[Mattaboy]

The boot out Charley White described is what I’m getting at.

cesare my skis are 95 underfoot.

I remember doing some math to find the angle for boot-out with targas, and I think it ended up being about 45degrees. That might feel extreme, but I’ve definitely hit that angle and spun out before.

Ultimately my use case here is skiing Mt Washington. I’ve just sourced some F3s and I want the binding I use to be able to handle Mt Washington terrain, which is why I’m asking about bootout. Front runners are the Meidjo and the Transit.

The uphill weight of the transit is compelling, but the cable routing seemed to be similar to the switchback, so I thought I’d ask if folks knew something I didn’t.

[cesare]

I guess I'm not the right person to answer since all my skis are wider than 95 and I ski in TX-Pros and Lynx in Hokkaido. 40+ days this year and only one was not powder. Before Lynx I used all manner of TTS bindings and before that Switchbacks on Dynastar Nobis Inspireds, which are 89. Never had a problem with boot out on those in Colorado but I did one time on a steep fall from a hanging glacier with much narrower skis that cost me seventeen fractures and a lacerated heart. So I understand the concern.

It doesn't seem to me like there is a huge difference in weight between Meidjos and Transits but the performance will be quite different. Meidjos are not as active as Lynx, but they are active enough to satisfy big boot, hard charging skiers. I don't know how active you can get the Transits to go but since they also do not have underfoot cables and a plate connecting to the second heel, they will feel a lot looser or more neutral. On the other hand, the tech toe will also give them much greater power to the edge than you had with Switchbacks. It's a whole new world skiing with tech toes both uphill and down.

[jtb]

I have TTS with Voile side springs and F3's on a 95uf ski and have not booted out when carving groomers. I suspect tucking the pivot rods under the foot and placing the heel throw on the heel shelf reduces the problem compared to a hardwire. The springs are really tight to the boot on TTS. However, that does introduce the problem of the boot sometimes contacting the rods or springs in a turn and bending them. I do have that problem and suspect you would too if you try carving groomers on the Transit.

Edit: also, thanks for the clarification and sorry for the misunderstanding and thread drift

This is what I mean about TTS placing the springs tighter to the boot than 75mm. All skis shown below are <90uf.

[Manney]

Risers common in slalom and giant slalom. Reduce possibility of booting out on hard groomed surfaces. Not so much of an issue in recreational pow because of speeds and snow resistance. Some insights here… mostly all about creating an even playing field…

https://assets.fis-ski.com/image/upload/v1658092621/fis-prod/assets/Specifications_for_Alpine_Competition_Equipment_09.07.2022.pdf#page11

Gotta dig a bit… start looking at component interfaces.

[Manney]

Lots of things that affect geometry… especially outside competition where there are no hard limits… ski width under foot and camber, stiffness being major ones besides bindings.

everything comes at a cost though

[xmatt]

It doesn't seem to me like there is a huge difference in weight between Meidjos and Transits but the performance will be quite different.

In fact, Meidjo weighs less than Transit does in total. But, if you remove springs from Transit, the Transit weight is less. After thinking about it, I've decided that overall I count that as lower weight for Transit. I ski both Meidjo and Moonlight (which is very similar to Transit, I think), and while it takes a short amount of time to add and remove springs on Moonlight, overall transitions are faster on Moonlight. That is, under ideal conditions, the fastest is Moonlight without removing springs, next fastest is Meidjo, and slowest is Moonlight removing springs. But, under non-ideal conditions, I sometimes wind up chipping snow out of Meidjo when I transition and that occasional loss of a lot of time means that overall I think Moonlight removing springs is faster than Meidjo. But my transitions, while relatively fast compared to many people I tour with, are still painfully slow by skimo race standards so maybe it is more about convenience than actual time. I mean, if you are on a narrow ridge with wind above a steep slope, it's more about doing everything smoothly than about doing some acrobatic move to save 30 seconds.

[muffin]

I've never booted out on TTS, even at high edge angles where the side of my kneepad grazes the snow. My skis are 72mm wide and my pivot rods are tucked under my boot like in jtb's pictures. Skiing groomers.

I knock the cables off occasionally like jasonq describes. Usually I stay in the toe and don't realize what happened until I drop that knee and the binding free pivots about the toe. Mildly terrifying, even on an open slope.

[Paul Lutes]

Risers common in slalom and giant slalom. Reduce possibility of booting out on hard groomed surfaces. Not so much of an issue in recreational pow because of speeds and snow resistance. Some insights here… mostly all about creating an even playing field…

https://assets.fis-ski.com/image/upload/v1658092621/fis-prod/assets/Specifications_for_Alpine_Competition_Equipment_09.07.2022.pdf#page11

Gotta dig a bit… start looking at component interfaces.

I'm a little confused as to why you keep throwing up Alpine/fixed heel FIS rules instead of Telemark/free heel FIS riles (https://www.fis-ski.com/en/inside-fi...ary/telemark)?