Clockwise from left, 4 different types of ski boots and ski bindings.

Understanding Ski Boot to Ski Binding Compatibility

This is Not a Compatibility Chart: The Excuses

Let me preface this by saying that an answers-all breakdown of boot-binding compatibility would need to get specific by brand, model, and model year, while accounting for all models, and years, from each brand, and any possible inter-brand combination thereof – which this does not.

On top of that, boot-to-binding is only half the equation. Binding-to-boot compatibility is its own interconnected, but-not-always-inversive beast.

It’s an annoying answer (especially if you came here for specifics), but truly, the best way to guarantee a given boot will be compatible with a particular binding is to consult the manufacturer’s most current compatibility-related materials.

Excuses adequately established, there are some things you can, and should, know about your boots that will make identifying compatible bindings much easier…

Understanding Boot-to-Binding Compatibility: The Point

The following information, broken down into five categories, will provide the foundation you need to determine the compatibility of a specific ski boot and ski binding, on your own. These categories are: Standards & Certifications, Types of Boot Soles, Boot Sole Length, Boot Flex, and Boot Sole Wear.

What Do Boot Standards Mean? DIN, ISO, and TUV Explained.

Let’s start with the organizations who provide the standardization that makes inter-brand compatibility possible in the first place. Their acronyms are used all over the place, and help consolidate the specifics of the lug measurements, sole types, and other features they’re referencing (more on that later). If you have no desire to understand the why behind boot-binding compatibility, these acronyms will usually get you to that top-level yes/no answer you’re looking for.

DIN (Deutsches Institut fur Normung)
Not to be mistaken for release force setting – which it’s used interchangeably with these days – DIN is a German organization that sets standards that specify requirements for products, services, and processes. In the ski industry, DIN is used to standardize everything from measuring the geometry of skis to categorizing types of ski boot soles. In other words, “DIN” isn’t a binding setting, but rather the organization that Normung-ed the denotation of release force settings in ski bindings.

ISO (International Organization for Standardization)
To grossly oversimplify it, ISO is the international version of DIN. They provide the requirements, specifications, and guidelines that ensure international consistency of goods and products. Within the ski industry, there is a ton of overlap between ISO and DIN standards, and you’ll often find products that reference a DIN ISO numerical classification (this is a standard adopted by DIN).

Note that not all boots and bindings have been standardized by ISO, which doesn’t mean they’re unsafe or generally incompatible – it literally means that they’re not standardized by this specific organization. Typically, it’s because they feature some sort of new-to-market technology that hasn’t yet been standardized by ISO.

TUV (Technischer Uberwachungsverein)
TUV is a little different in that a TUV is an independent German safety monitoring and testing company that runs in-depth, truly comprehensive tests of technical products. The successful completion of these tests results in a TUV safety certification. Within the ski industry, “TUV-approved for…” is a term you’ll come across when researching boots and bindings. Generally, it’s referencing the tested-and-proven compatibility between different DIN/ISO-categorized products.

Now, it’s worth mentioning that TUV conducts these tests for profit. Which doesn’t mean they’re biased or unreliable or corruptible in any way – TUV is highly respected. It’s more something to keep in mind when assessing products that are not TUV-approved. The TUV stamp comes at a price, and not all companies have the resources or desire to seek it out.

There are more, of course – EN, CE, SUD – but DIN, ISO, and TUV are the big three you’ll come across, and they’re the acronyms you’ll find used as a compatibility spec.

What Type of Boot Soles Do You Have?

ISO 5355 (Alpine)
ISO 5355 refers to most ski boots with “traditional” alpine soles. ISO 5355 ski boots are further categorized by Adult Alpine (Type A), and Junior or Children Alpine (Type C) ski boots.

ISO 9523 (Touring)
ISO 9523 refers to most ski boots with touring (or Vibram) soles. These soles typically feature some form of “rockered” profile and/or a rubber compound designed to make walking easier and more comfortable.

Walk-to-Ride (WTR)
WTR is a sole-binding system. On your boots, WTR means hard-plastic toe and heel pieces with a slight rocker (in other words, less than Touring soles) designed to enhance walking comfort. WTR bindings, meanwhile, are bindings designed specifically to accommodate those WTR soles (and almost always Alpine soles, too).

GripWalk
GripWalk is a sole-binding system from Marker. On your boots, GripWalk means co-polymer soles with a rocker profile designed to enhance walking comfort. GripWalk bindings, meanwhile, are specifically designed for these soles and require no toe-height adjustment for either GripWalk or ISO 5355 Alpine soles.

WTR and GripWalk are not currently ISO standardized. Both WTR and GripWalk are compatible with some ISO 5355 Alpine soles, but not all. This is where the importance of toe height (specifically adjustability) comes into play.

Do You Have Adult or Junior Lugs?

Lugs are the primary interface between the boot shell and binding, and as a result, they are critical to boot-to-binding compatibility.

All Alpine ski boots come with either adult norm lugs (Type A) or junior norm lugs (Type C). Whether a lug is considered adult or junior is a matter of sole dimension norms, as determined by ISO/DIN specifications. It is important to note that the manufacturer’s categorization of a ski boot (adult vs. junior) is not a foolproof indication of which type of lug it will have. For example, some “junior” ski boots are equipped with adult lugs.

Since the dimensions (height, width, and length) of the lug differ from Type A to Type C, the binding’s ability to properly retain/release the boot is directly tied to its compatibility with adult or junior lugs. For example, a junior lug in an adult binding will not be big enough to properly interface with the heel/toe cups and anti-friction device (AFD), which means the binding can’t do its job. This incompatibility is not always obvious – it’s possible to “click in” without being properly and safely engaged.

In order to assure proper forward pressure, it is critical that your bindings are both compatible with your boots’ lugs (adult vs. junior norm) and mounted for their specific sole length (see below). Adult-norm bindings are not compatible with junior norm boots. And while most junior-norm bindings will accept adult-norm boots, the scenarios in which that is an advisable setup are rare.

What is Your Sole Length?

Ski boot sole length is the distance from the front of the toe lug to the rear of the heel lug, measured in millimeters. Sole length is not uniform across Mondopoint sizes. For example, two pairs of 26.5 ski boots from the same manufacturer may very well have different sole lengths. To find the specific sole length of your ski boots, check for raised markings at common points such as the inside or outside of the heel lug, or at the midpoint of the sole.

Knowing your sole length will allow you to determine whether a binding’s adjustment range will accommodate your boot. If your sole length is too short, proper forward pressure can’t be set. Too long and you won’t even be able to step in.

What is Your Flex?

Ski boot flex index is an unstandardized method (used industry wide) for denoting the approximate force required to engage the boot. Flex, press, bend, crush – whatever you want to call it – this is a “measurement” of how much oomph it takes to move the upper cuff. Typically, anything under 75 would be in the realm of junior boots, while 75 and above spans the full (adult) range from ultralight beginner to heavyweight DH racer. Determining the “right” flex for you is a matter of weight, strength, ability, and plain old personal preference.

In many ways, flex index can be thought of along the same lines as the DIN setting on your bindings. Let me be perfectly clear, I’m fully aware of the safety implications of proper release tension; this is only to compare the similarities between determining factors.

When it comes to boot-to-binding compatibility, flex index is important mainly because of implication, or what can be assumed. For example, if you’re in a 75-flex boot, you shouldn’t use a 20-DIN full-metal race binding – the assumption being that said binding is attached to a terrifyingly stiff race ski that is way outside of your ability range. Conversely, if you’re in 150-flex plug boots, the assumption is that a 10-DIN composite binding will not be adequate for your weight and III+ skier type.

Are Your Toe and Heel Pieces Worn Out?

Replaceable Toe/Heel Pieces:

Replaceable toe and heel pieces ensure that normal wear-and-tear caused by walking does not prematurely end the life-cycle of your ski boots. Replaceable toe/heel pieces do not mean invincible boot soles. It’s important to closely monitor your boots and always replace toe/heel pieces well before any wear reaches irreplaceable parts of the boot sole. Otherwise new toe/heel pieces may not properly seat and/or fully touch, thereby compromising the boots ability to properly interface with the binding.

To determine if your replaceable toe/heel pieces are too worn for safe use you should always bring your boots to a ski shop that has a binding adjustment and testing machine. This machine will allow a trained technician to accurately asses whether your boots are engaging with bindings properly – i.e. that release force settings are an accurate reflection of the force required for proper release. Anything less than machine testing and you’re playing a guessing game with retention.

That being said, you can (and should) give your replaceable toe/heel pieces the eyeball test on a regular basis to know whether a machine test is worth pursuing. Carefully inspect the toe and heel of each boot and look for areas in which the material of the replaceable portion is creeping close to the solid plastic of the shell (the part that can’t be replaced). Also, look for uneven wear, which can compromise the binding’s ability to apply even, proper retention force.

Solid Lugs:

Some ski boots, such as ones designed specifically for racing, forgo replaceable toe and heels pieces in the name of the maximum energy-transfer efficiency of solid lugs. If your ski boots are equipped with solid lugs, closely monitoring their wear is of the utmost importance. Improper contact between boot and binding caused by worn lugs can result in premature release – both laterally and vertically.

With solid lugs you should forego the eyeball test and rely solely on machine testing. Without the clearly defined border between replaceable and irreplaceable, it’s more difficult to determine how much material you’ve lost, and thus, how close you are to reaching the threshold where bindings can’t properly interface with your boots.

In Conclusion

With the information provided above you should be able to understand what to look for, and what questions to ask, in order to determine if your ski boots are compatible with a specific binding. Again, for a definitive answer, manufacturers’ most current compatibility-related materials will always be the way to go.

If you have specific questions regarding boot-to-binding compatibility, please feel free to reach out to our Experts directly at cs@jans.com

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