CAST SI&I Alpine Touring System

Technical Overview of the SI&I System

In general, the plate system is very simple. For the toe: You attach a base plate to the ski that allows you to attach an FKS toe piece, or a Dynafit Radical toe piece.

CAST SI&I System, Blister Gear Review
CAST SI&I System with Dynafit and Look Toe Pieces.

(Note: other bindings are supported as shown on the Kickstarter website.)

Both toe pieces are also attached to a plate. The toe piece plates slide under 270 degrees of flanges on the base plate and lock to the base plate with a stainless steel sliding lock.

The base plate of this system is cast aluminum that is machined to high tolerances using a CNC machine. The toe piece plates are laser-cut aluminum. Both plates are then hard anodized and coated to reduce icing. Both toe pieces are connected to the plates with machine screws and stainless steel inserts that are pressed in from the bottom of the plate and include a flange to increase their resistance to pullout. The pullout strength is much higher than that of a binding screw into a ski core.

Note: My prototypes did not have the flange, and a lot of folks have put many aggressive vertical feet on that system with no known issues. This new design with the flange will be even stronger.

[Editor’s Note: In case you’re wondering what “agressive” means here, we’re talking about the most agressive skiing in the world. Look up any comp footage of Lars, Silas, Dylan Crossman, or Tom Runcie. It’s not that this system is only for people skiing the rowdiest lines out there, but the system was certainly designed and tested to handle the rowdiest lines out there.]

The heel piece of the binding is lifted off the ski to maintain the ramp angle of the alpine binding. This is done with a high-density injection molded plastic that is 7mm thick. The climbing bails are also integrated into this piece:

SI&I Heel Piece, Blister Gear Review
SI&I Heel Piece

The Boot

Ah, yes, the boot. In my mind, this is the toughest part of the system in terms of the production run logistics. Obviously, a standard Lange RS130 or alpine DIN toe is gonna be a bit squirrely in a tech toe. So what was done to my boot was simple.

Lars had a jig that my DIN sole slid into, and we (by we, I mean Lars worked while I watched) drilled two holes into each side, tapped, epoxied, and threaded in an insert.

We then used a countersink bit to make ‘er work. It was quick, cheap, and funky, but I love it.

CAST Tech Fitting Boot, Blister Gear Review
Joe’s Tech-Fitted Lange RS.

The new SI&I system, however, incorporates a true tech fitting (more on this below) that is definitely a more bomber setup and looks more durable. The logistics of mailing in your boot and paying for this work is not the most appealing, but it’s well worth it. And I look forward to the day when every good shop in the world is able to do this modification.

Touring Setup

To tour up, you install the Dynafit toe in the base plate, strap up your brakes with a Voile strap, put on your skins, and run up the hill.

If you get to that point in the tour where it is no longer flat, you reach down, raise a climbing bail, or maybe even both if you are feeling aggressive, and you keep going.

At the top, you unstrap your brakes, and if you were sharp enough to have remembered to bring your FKS toe piece, you swap out the Dynafit toe piece, stick it in your backpack, and you ski down.

It truly is that easy.

The new climbing bails are similar to my current system, although more bomber, and adjustable with two degrees of elevation. I have had no issues with my bails, and they work well around a 0 degree and 10 +/- degree tour. An update on the new bail system will definitely be needed, though I don’t have any immediate concerns.

 

29 comments on “CAST SI&I Alpine Touring System”

  1. Nice review, thanks!

    But one thing is wrong: it makes a huge difference if you have more weight on moving parts or in your backpack. I wouldn’t change the system, it seems just fine. The difference is the acceleration needed on moving parts: the heelpiece of the binding has to be accelerated each step if it is on the ski by your foot. If it’s in the backpack that acceleration is not needed because the upper body doesn’t have to be moved like that. Consider a bicycle wheel and attach some weight to it, the farer away from the axis, the stronger you have to pedal – same with boots, bindings and skis, they are moving to get you up. The torso itself doesn’t move, it is moved. Just go running with you skiing boots on and compare it to having them in you backpack and notice which one costs more of youre legs energy.

    sorry for my lacking english skills

    • Hi, Burny – I agree with your point. What I was focusing on was that removing the weight of the binding from the heel of the boot during touring is the major benefit, and that is more important than reducing weight on the ski.

      Not only are you accelerating that extra weight on the heel, but you are also pivoting and lifting it up and down with every step. The ski stays at a consistent height compared to your torso, and is moved the same number of vertical feet. Since nobody’s going to use this system for rando racing, I was emphasizing that this a bomber alpine system that also tours incredibly well compared to anything but a full tech setup. Some people will want that removable heel for the reason you mention, I’m just not one of them.

      But you make a great point, we will revise and try to clarify. Thanks for reading and for the comment.

      • Yes, that’s totally correct – in fact that is one of the major benefits of the dynafit invention. It’s great to see that idea in combination with a true alpine binding. The system Silas and his brother came up with is so simple, yet it seems the right path.

  2. Joe, you downplayed having a removable heel piece but the reason I would be very interested in that option would be to have the same flexibility as the MFD system and swapping to other skis. For $75 you can get the mounts on another set of skis and just swap the MFD plate around on different sets of skis (assuming brake width is adequate for the various sets of skis). Without the removable heel piece with the CAST system, you need to own/buy another set of bindings for another set of skis you want to make compatible. Am I missing something in my logic? MFD is a very cost effective way of making multiple skis AT compatible, especially when I paid just $140 for a new MFD system.

    By the way, love all the write ups. Thanks.

    • Slide,

      I mentioned this briefly at the end of the section discussing the removable heel. To me, I’d rather deal with binding freedom inserts on he heel (half as many as the total binding, not too bad) and not have the added weight skiing, or the manufacturing cost. You are still able to swap all bindings between skis, although now it will take 5 minutes versus one. It’s all a personal preference. I completely understand wanting the swappable heel plates, but they aren’t for me personally.

      The added 5 minutes of switch over time in the garage will be saved by the quicker skin to the top when compared to the MFD.

      And the swappable heel plates will be a reality some day, but this project started off to make a bomber touring setup, which they did. Once we fund that, who knows what CAST will come up with next, but I guarantee that swappable heels is on the list.

    • Rob,

      Going up you’ll be on just the dynafit toe piece, so that would work fine. Going down, you’d have to check the compatibility of the boot with your current alpine binding setup. Personally I feel you need a sliding afd to work with vibram soles, but some people have made them work by modifying the toe piece or the boot sole.

      Joe

      • For the latest on AT/technical boot compatibility with alpine (DIN) bindings – see Backpacker Magazine, Sept 2014 (pg 46). Engineers at Uni Of Washington/Seattle tested 120 combos of AT boots & alpine bindings for their release capabilities. And found that very few combos will release correctly. Even if the boot fits into your alpine binding, you’ll very likely never be sure it’ll release when or how it should. And you may even be damaging those bindings. Hmmmmm…

  3. I H8 those dorks behind me who freely mooch off my trail breaking efforts and then have the unmitgated audacity to poach my pow line. (there’s got to me a snowmenclature term for that!)

  4. Quick question that I have due to looking at the above pictures.

    One of the benefits of the Pivot system, is that your heel can “pivot” out when the binding releases. However, looking at the pictures the, side of the risers when locked down look as if they would prevent this from happening as the boot heel would catch on them.

    This seems a pretty big problem or is it just the angle the pictures are taken from??

    Thanks.

    • Steven,

      I don’t have the updated system yet (should in a few weeks here and will update). But I believe it is the angle of the picture. I can’t imagine that would be an issue. Although I do see what you are looking at.

      I’ll update when I receive the new setup.

      Joe

      • Thanks.

        Yea, it would be very odd for that to be the case, but would still be good to have an affirmative answer.

        Enjoy when it arrives! I’m jealous!

  5. Hello,

    I’m thinking of getting a Cast setup and had an auxiliary question. What’s your opinion on riding bindings at the very lowest end of its DIN setting (8 in the case of the CAST-compatible FKS18)?

    Thanks

    • Vince,

      There are a couple good write ups on the site in the Bindings 101 and 201. These discuss this exact question.

      Personally, if you are going to rock a p18 on 8, I would be inclined to go with a p14 to save weight. The toe is a slightly different design, but you still get all the benefits of the pivot heel.

      If you aren’t concerned about weight, there is no reason you can’t run a p18 at the low DIN setting.

      Joe

      • There exists such a thing as a single-pivot toe in a 6-15 DIN: Rossi FKS155. Once I get the new (apparently only available in Canada, suckers :P) WTR compatible AFDs for them (just to be clear, only for single-pivot toes, no such thing for 14 DIN toes), and some wide brakes, I’ll have a pretty sweet setup for my Kuros. Oh, and save up $275USD at a craptastic exchange, guess I shouldn’t have mocked y’all.

        Joe, couldn’t agree more about single-pivot Look/Rossi, and about sliding AFDs. Sounds like you value your knee ligaments as much as I do.

        All this effort to be able to use one set of boots for alpine and touring, which is key when you gotta fly to the goods.

        Andy

  6. Nice write up on the CAST system. Quick question. Does the dynafit crampons work with the Cast plates? Looks like it should fit no problem but would be nice to get a confirmation that they don’t interfere.

    Slightly off topic but do you know if a BD Factor 130 w/AT sole fits in a Look P14 toe piece. Deciding between them or the Salomon STH2’s to pair with a CAST setup.

    Thanks in advance,

    Supra

  7. I imagine you Joe or some of the other guys at Blister will have put a bunch of more days on this system this season. It would be really good for another update, especially as I read they have dropped the weight down to 180g per ski.

    • Considering the snow in Tahoe this year…unfortunately I haven’t put a “bunch more” days on these. However, I’ve put enough on them that I have stopped even looking at what else is coming down the pipe line in terms of AT setups. IMO, there isn’t a design that compares if you’re looking for a system that is alpine oriented. It makes almost no compromises on that end, while being very efficient on the touring end when comparing to a Duke, etc. I always joke with my buddies when I’m switching over about how “inconvenient” the system is to transfer over. Some folks think/say it’s a pain. But it’s only the folks that have never used them that have those comments. They are awesome, on all fronts, period.

    • …or any frame AT system for that matter. Brilliant thought. TotAlly blows away the foregoing discussion. Well played, sir!

  8. Hey all. I realize this is an old thread but the Blister site is pretty active and generally has helpful comments so I figured I would post this here.

    I have been using (and loving) the CAST SI&I setup since their kickstarter campaign. It’s totally bomber on the downhill and tours great going uphill with only a minor delay when switching over (seems comparable to the swap time of my old dukes, mostly because you have to take your boot out of the binding during the changeover). I’ve ran into a discouraging issue this fall, however, when trying to use a pair of Scarpa Freedom RS boots. It seems the rockered “Mountain Plus” sole (the ones with the tech toe piece) will not work with Look Pivot toe pieces (too low of a stand height, around 20mm). This means the incredibly popular Scarpa Freedom boots can’t be used with the SI&I system unless one was to modify the “Piste” (DIN) sole to have a tech toe.

    Does anyone have experience with this issue? It’s a pity they aren’t compatible as they are both awesome products.

  9. One year after the last guy…but I’ll give it a shot.

    The last two seasons I have toured with my snowshoe/snowboarder friends, key is we ALL use snowshoes. Needless to say, this is probably the most annoying and heaviest way to tour, as I was putting my alpine boots and my skis on my back. This year, I refuse to keep doing this and would like to purchase a touring setup. However I don’t like the idea of sacrificing a pair of skis to touring since I will only do it about 5-10 times a season.

    I am still planning on getting a pair of WTR boots, potentially Salomon’s, and have been considering the Marker Kingpin. But this means on ski trips I still have to bring two pairs of skis. I like the Cast system because you get the best of both worlds on one pair of skis, as well as not sacrificing the performance of the alpine binding inbounds or in rough out of bounds conditions. Am considering this system with the Look Pivot 14s. Are the WTR AFD plates needed for the 14s or only the 18s? Or was it only for Scarpa?

    I have no previous experience on pin bindings, but the idea of them going downhill seems crazy. How would you rate this system compared to whats out there for the 16-17 season?

    • Hi Elise:

      I know this is a late reply and you’ve probably already purchased your bindings and have been skiing on them all season, but here are answers to your questions in case it helps you or others:

      Boot Compatibility:
      Keep in mind that WTR is a design specific to Lange and Rossignol boots, so technically WTR AFD plates are only certified to work with Lange or Rossi boots with WTR soles. That said, they might work with other rockered soled boots.

      If you buy rockered soled boots or WTR boots, you will need one of the following bindings:
      1) New Look Pivot 14 Dual WTR bindings (switchable AFD between WTR and DIN boot soles)
      2) Look Pivot 18’s with aftermarket WTR AFD plates (CAST sells these replacement plates, they seem to be rather rare but CAST must have bought up a stockpile directly from Look)
      3) Choose another binding with adjustable height AFD, Marker and Salomon both make adjustable height AFD bindings and CAST made systems for both brands of binding.

      If you choose to buy non-rockered boots and do a CAST tech sole conversion:
      1)Use old-school solid plastic soled boots and DIN standard AFD’s on Look Pivot 14 or Pivot 18.

      I sent CAST a pair of solid-plastic soled boots from 2008 and they did a great job on my boot sole conversion. If you want to put tech inserts on a different boot (not solid-plastic soled) you will need to contact Lars at CAST and find out if he can convert it for you. Since Lars’ personal boots in his videos are race boots with solid plastic soles, I suspect that the solid sole conversion systems have gotten plenty of R&D.

      How I would rate these bindings compared to other AT options this season:
      All told, the CAST system is more expensive than most of the other burly AT binding options, but it is the only system that does not sacrifice performance anywhere (climbing efficiency or skiing power and security). I’m sure other people on the internet will argue, but those people probably think that Marker Kingpins (or insert favorite tech binding here) release and retain their boot just as well as Look Pivot 18’s. I don’t think so. If you want to be able to ski resort and backcountry terrain on the same solid setup, without missing a beat or ever second-guessing your equipment, CAST is the best option. If you can afford to have a quiver of skis, boots and bindings and don’t mind changing from one setup to the other from resort to backcountry to optimize for skiing vs climbing depending on the day then there are other viable options out there.

      I hope this helps! I have been skiing the resorts on my Look Pivot 18 CAST system all winter and they work flawlessly. I can charge hard in my race boots or my softer CAST converted tech boots (same BSL, DIN standard soles) without making any adjustments to my bindings or skiing style.

      I have only used the walk-mode of the bindings 3 days this season, and those were mostly shake-down runs for my new toys. The changeover was a little fiddly if I got snow in the interface, but I have since rubbed some Holmenkol yellow ski wax on the interface to keep snow from sticking and I’m planning to do some spring tours in the coming months to try them more. I love the confidence of clicking into my Look Pivots on the changeover, I have always skied on race bindings and I know when they’ll stay on or come off. With Look Pivots I can run a nice safe-for-my-knees DIN of 10 without having pre-release problems.

      Cheers!

      Clayton

  10. I am still using these in 2024.. you could get these with a lot of different bindings with the originals. I am still running marker squires and K2 pinnacle-mind bender boots. The only time I had a pre release was when I skied into a stream. Like them a lot.

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