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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 need 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 binders 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 specifications.  Luckily, the gaps have become fairly standardized and there are only three sizes from which to choose.  Here are the details:

Dynafit Binding Heel Gaps
Low Tech Race 1 & 2 4mm
RC1 4mm
Superlite 1 & 2 5.5mm
Speed Turn 1 & 2 5.5mm
Speed Radical 5.5mm
Radical ST / FT 5.5mm
Radical 2.0 0.15mm
Vertical ST / FT 5.5mm
Plum Binding Heel Gaps
Race 135 - 185 4mm
Guide / Yak 4mm
Ski Trab Binding Heel Gaps
TR-Race / Adjustable 4mm
Gara Titan 4mm
Gara Titan Release 5mm
Hagan Binding Heel Gaps
ZR 4mm
La Sportiva Binding Heel Gaps
RSR 4mm
Kreuzspitze Binding Heel Gaps
SCTT 6mm
GT 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 it 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 it’s possible to do this free hand if you have patience and skill.

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 bindings, a few twists with a Pozidriv screwdriver will set your gap, though a flathead will do in a pinch.  For Trab bindings on the other hand, a socket wrench is 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.


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!
Reply to this comment:

Comment from Stano 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 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 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 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 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:

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