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11/17/2021 Mind the Heel Gap

Londoners and Dynafit binding owners tend to be very mindful of gaps. The city-folk are reminded to look out for the gap between train and platform when stepping onto the tube (British for subway). The ski-folk needs to keep an eye on the gap between the back of their ski boots and the heel towers of tech bindings. These are important since forgetting either can lead to falling on one’s face. In this article, we will focus more on ski binding heel gap than the type that can be found underground.

Tech binding heel gaps have been present since the original pin-style bindings were designed by Fritz Barthel in the early 1980s. Unlike most alpine bindings, the toe and heel units on current models of lightweight backcountry bindings do not slide forward or backward when under pressure. That means another mechanism is required to allow skis to flex naturally. This problem was solved with metal heel pins that are designed to slide in and out of tech fittings on a ski boot. By placing a gap between the heel tower and ski boot, tolerance was added for skis to flex as the pins can dive deeper into the boot.

The question is, how much gap should there be between the boot and heel unit? Or asked another way, how much should the metal pins slide into your boot? If there is too small of a gap, the metal pins become fully inserted into the boot and the heel tower itself collides with the boot. This can prevent the release mechanism of the binding from working properly. If the heel gap is too large, your release values might end up on the low side causing pre-release and the aforementioned face plant. In extreme cases when the ski is flexed in reverse, say when picking up your foot lodged in deep snow, the pins can pull out from your boot completely. Therefore, it’s crucial for optimum performance of tech bindings to have the gap configured correctly.

The first step in ensuring you have the right heel gap is knowing the manufacturer's specifications. Luckily, the gaps have become fairly standardized and there are only a few sizes from which to choose. Here are the details:

ATK Heel Gaps
Candy / Crest 4mm
Haute Route 4mm
Raider / Freeraider 4mm
Revolution / Trofeo 4mm
Atomic Binding Heel Gaps
Backland Tour 4mm
Black Diamond Heel Gaps
Helio (all) 4mm
Dynafit Binding Heel Gaps
Low Tech Race 1 & 2 4mm
RC1 4mm
Expedition 4mm
Superlite 150 5.5mm
Superlite 1 & 2 / 175 5.5mm
Speed / SpeedFit 5.5mm
Speed Turn 1 & 2 5.5mm
Speed Radical 5.5mm
Radical ST / FT 5.5mm
Radical 2.0 0.1mm
Rotation 10 / 12 0.1mm
Rotation 7 / Lite 5.5mm
Vertical ST / FT 5.5mm
Fritschi Heel Gaps
Vipec / Evo 1mm
Xenic 1mm
Fischer Heel Gaps
Tour Race 1, 2 & 3 4mm
G3 Heel Gaps
ION (all) 0mm
ZED 9 / 12 0mm
Grizzly Heel Gaps
GR 98 4mm
Olympic 4mm
Marker Heel Gaps
Alpinist 0mm
Plum Binding Heel Gaps
Race (all) 4mm
Oazo / Pika / WEPA 4mm
Guide / Yak 4mm
Summit 4mm
Salomon Binding Heel Gaps
MTN 4mm
Ski Trab Binding Heel Gaps
TR-Race / Adjustable 4mm
Gara Titan 4mm
Titan Vario / Release 5mm
Titan Vario.2 0.75mm
Hagan Binding Heel Gaps
Core / Core Pro 4mm
Ride / Pure 4mm
Ultra / ZR 4mm
La Sportiva Binding Heel Gaps
RSR / RST 4mm
Kreuzspitze Binding Heel Gaps
EL 6mm
RS / RS-A 6mm
GT / GT 2.0 6mm

So how do you set the heel gap correctly? That mostly depends on whether your heel piece has a fore/aft adjustment mechanism. If the heel does not adjust, you have a race binding and it needs to be mounted precisely for your boot. Binding manufacturers provide their dealers with jigs designed to make setting this gap a snap, though with manufacturing tolerances you can't blindly trust them. We specialize in fixed race mounts at Skimo Co and have custom tools and processes to ensure accuracy. This means that, uniquely, we can guarantee a precise race mount.

Adjustable bindings, on the other hand, let you work with various boot sole lengths. Ranges of 20mm to 40mm of adjustment are typical. With Dynafit touring bindings, a few twists with a Pozidriv screwdriver will set your gap, though a flathead will do in a pinch. For Trab adjustable bindings, a socket wrench may be needed. Plum includes a mini Torx key with their adjustable bindings. Whichever the tool, you will have some flexibility when it comes to changing boots and a margin for error when mounting by hand.

To help measure the heel gap, some manufacturers include various shims that approximate their specified heel gaps. These should slide snugly between the boot and the heel housing. For adjustable bindings, you can tune the fore/aft settings with the shim in place until it fits. See below for a sampling of the shims that might ship with your bindings.

If you do not have a shim, various arrangements of pocket change will do the trick. Two unworn nickels measure just under 4mm, and adding a quarter will approximate the 5.5mm gap. Alternatively, a cheap set of metric hex keys makes a great heel spacer kit.

In conclusion, it is important to be mindful of your tech binding heel gap, sometimes referred to as the “tech gap”. You should only need to set it once per boot configuration, but please make sure it is as close to manufacturer spec as you can get it. If you would like more frequent reminders of gap dangers, we recommend a sightseeing tour of the London underground.

This article was originally published on 12/26/2013 and was last updated on 11/17/2021.


Comment from Ben
I have a pair of Ski Trab Titan Vario 1 bindings, but they are mounted with the ATK adjustment heelplate, not the bulky Ski Trab heelplate that comes with the bindings. Since I am mounting these heels "race style" should I have a 4mm gap like the Gara Titan or a 5mm gap as is recommended for the Vario 1?
Reply from jbo
Hi Ben, the Vario 1s need a 5mm gap, whether fixed mounted or on any plate. It's quite a nice distance that enables flat mode to work well also.
Reply to this comment:

Comment from Jerry
I just bought a pair of 2020 Dynastar Speed Turn 2.0 bindings. the Dynastar website recommends a 4mm gap, rather than the 5.5mm recommended here. Why the difference?
Reply from jbo
Hi Jerry, sounds like an error by Dynastar.
Reply from Jerry S
OK, thank you very much
Reply to this comment:

Comment from Peter
Just got new boots and I'm curious: how strict is the 0mm recommendation on the G3 ion? The shop that mounted them (and adjusted to the old boot) left about 2mm, and the 0mm gap now seems to provide a little resistance stepping in. Ok to split the difference? Unknowingly skied the 2mm gap for 3 years (shoulder shrug)
Reply from jbo
Oops Peter, that is a bit wide. But yes, we have slightly opened the gap to help with step in on some occasions (altering the rubber sole can also help) and it hasn't caused any notable issues.
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Comment from Steve
Why does Rotation 7 have a 5.5mm gap, while Rotation 10 has a 0.15 gap? Seems odd since they are both based on the Radical 2.0, right?
Reply from jbo
Hi Steve, the 7 pairs the rotating toe from the 2.0 with the original Radical (1.0) heel.
Reply to this comment:

Comment from Erik Sandelin
Recently bought a pair of new skis with new dynafit st rotation 10 and the heelgap adjusted to 0.15mm as above. After two very shorts runs the heelgap is now roughly 4-5mm on both. Ever encountered this behaviour? Is it related to the 10mm "travel" of the bindning?
Reply from jbo
Hi Erik, that doesn't sound good! You can notice some travel when stepping in if the brakes get hung up on the boots, but that isn't a permanent change. You may have something broken in the baseplates.
Reply from Erik S
I realise that i overestimated the gap When looking from above. The increase is not 4-5mm but still slightly lager than paperwidth. I also got the feeling the gap had decreased somewhat a couple of hours later. I am gonna a do a more careful experiment to be sure of ny observations :-)
Reply to this comment:

Comment from Brendan
After skiing around 5000 feet of brutal suncups, I came to find that both my boots had somehow forced themselves down past the pins on my Kreuzspitze GT heels units. They were flat on ski, and the pins were gouged into the plastic pretty good. I had set the gap carefully at 6mm. I've used this setup quite a bit, and never otherwise had this problem, but also never skied such an undulating surface for so long. I'm wondering how to avoid this. should I consider shortening the gap?
Reply from jbo
Hi Brendan, that's not good. You can close the gap 1mm to help if you plan on skiing a lot of suncups! Also, we convinced them to lengthen the heel pins a bit since the 2016 version you have; we have some that we could send you that are 1mm longer. It would require some binding surgery to install.
Reply to this comment:

Comment from David Stevens
Am I right in thinking Dynafit Rotation ST10 bindings have a minimal 0.15mm heel gap?
Reply from jbo
Hi David, that's right! You should be able to slip a piece of paper in there but that's about it.
Reply to this comment:

Comment from Marc H
Hey guys, do you know the gap of the old Dynafit Tour Lite Tech heel? It's grey, blue and red with a metal post as the high riser? I assume its 4mm, but the pins are quite short and there's a plastic nub that protrudes between the heel pins. Thanks.
Reply from jbo
Hi Marc, most of those older "classic" bindings were 4mm. I can't be certain without a photo, but you're likely correct.
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Comment from Jakob
Hi, I have a pair of Hagan ZR Bindings mounted with a 4mm gap. Now I am thinking about switching to new boots with a 2 mm shorter BSL which would mean a 6mm gap (assuming accurate measurements and a similar distance from the front edge to the toe inserts). I read somewhere that some people mount the ATK race bindings with the 5.5 mm gap to be able to rotate the heal 90° for a flat position. If 5.5mm works I am guessing 6mm will be fine without a remount as well. Does anyone have experiences with that?
Reply from jbo
Hi Jakob, the official BSL marks aren't perfectly reliable when calculating precise heel gaps. That said, it is likely possible you can ski at a 6mm gap, noting the release value will be very different and you may need to adjust accordingly (style or locked vs unlocked).
Reply to this comment:

Comment from Martin
Hi, thanks for the article. I recently purchased Dynafit Radical 2.0. In my mind the shop has set them to the traditional 5.5 mm gap. Is there a way to check/change the gap to the exact specs? I am worried if I just start guesstimating when trying to reduce the gap to 0.14
Reply from jbo
Hi Martin, you can clamp a piece of paper (~0.1mm) between the boot and heel, then back up the heel until it falls out.
Reply to this comment:

Comment from Alex
Hi. Thanks for a great article. I recently received some skis from a euro retailer. My boots are difficult to clip in and the 'tech gap' is certainly less than Dynafits recommended 4mm for the low tech race heel piece when measured with a 4mm Allen key. Would the heel piece wear in with time or should I return the whole thing to the retailer.
Reply from stephen p
Hi Alex, yes, a tighter gap can increase the entry and release forces. Unfortunately the gap doesn't change over time with a fixed mount.
Reply to this comment:

Comment from CER
I'm assuming the gap on the PDG binding is the same as the Low Tech Race 2.0 at 4mm? Thanks!
Reply from jbo
Hi CER, yes, that is a 4mm gap as well.
Reply to this comment:

Comment from Scott S
And the gap for the RC1 binding? 4mm?

Reply from jbo
Hi Scott, just updated the list with some newer bindings. Yes, RC1 is 4mm.
Reply to this comment:

Comment from Stano at SkinTrack
On a different note but still on topic:

Sometimes, race bindings are hard to get in when they are new and get easier over time as the pins wear where needed. This could also be created by a too little gap which is totally possible to make since mounting a race binding is laser error margin process.

To fix the issue of problematic stepping when mounted correctly I have seen Euro mechanics file the pins a bit after mounting new skis - basically, wearing them down right away!
Reply from Rando Richard
By filing down the pins, does that only make entry easier, or would it also reduce the release value? As a 60+ skier (w/ big feet) using a pair of non-adjustable race bindings I am looking to back off the release value a little...w/o purchasing new heel units.
Reply from Stano at SkinTrack
In my opinion, filling down the pins does not change the release value per se. However, once pins are well worn out then your boot might pop out of the binding sooner if force is applied in the right/bad angle, however, such release would not be due to the heel spinning because the release force was overcome but due to poor conditions of the pins. Hope that makes sense.
Reply to this comment:

Comment from TZed
Does the TR Race and TR Adjustable binding use the same jig?
Reply from jbo
Good eye! The adjustable version is currently lacking in jig support. The toe piece works but the heel is left to paper and patience. At least there is some room for error on that one.
Reply from jbo
Quick update. The new TR2 binding jig also has holes for the TR Adjustable. It will be shipping in the fall.
Reply from TZed
Will you be carrying the TR2? It seems like with such limited boot options it will be a hard sell
Reply from jbo
Haven't made a final decision yet but it's unlikely. We're not in a position to push a new standard at our size, and it's not in our sweet spot of lightness. Definitely getting a jig though!
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