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Jan 07 2019

Crispi NTN duckbutts come up short!

Crispi sz small NTN sole is approx 2mm shorter than Scarpa TX (same mondo size - 26).

Crispi sz small NTN sole is approx 2mm shorter than Scarpa TX (same mondo size – 26) Photo by SkinnyG.

It appears there is a problem with NTN boots from Crispi; not all, but enough to give a warning. The second heel might be too small, meaning the distance from the toe-to-the-duckbutt is too short. The result is a loose, or unreliable connection with Meidjo and Outlaw bindings. At this moment there isn’t any reliable data on how widespread this issue is, but the nature of the problem is clear, out of spec boots from Crispi. While the problem has been noted by both 22 Designs and The M Equipment, apparently new Meidjo v2.1 springbox is slightly different than v2.0 and more prone to exhibiting the mismatch.


What’s the Spec?

All makers of NTN compatible bindings agree on the specified dimensions for NTN soles. Most importantly the originator of the norm, Rottefella, defines the length as follows:

  • Small: 158.5 mm (± 1 mm)
    (for BSL ≤ 306mm – Crispi/Scarpa sz ≤ 26.0, Scott sz ≤ 26.50)
  • Large: 176.5 mm (± 1 mm )
    (for BSL ≥ 307mm – Crispi/Scarpa sz ≥ 26.5, Scott sz ≥ 27.0)
The NTN sole length runs along the curve defined by the bottom of the sole (green) from the front of the toe to the back of the second heel, in the center.

The NTN sole length runs along the curve defined by the bottom of the sole (green) from the front of the toe to the back of the second heel, in the center.

The Symptoms

The problem surfaced when SkinnyG posted his experience in the BackcountryTalk forum, saying, “When my heel is down on the ski, the Meidjo claw partially disengages from the duckbutt.” He noticed “getting a lot of releases due to the duckbutt lifting out of the claw.”

In response to questions from the tribe at BackcountryTalk, SkinnyG determined that the length of his NTN sole was short of the spec, preventing it from being fully captured by the claw and pre-releasing. The length was shy by approximately two millimeters, double the specified limit.

Scope

While boots with a short butt have been noticed, it is not the majority. With maybe a dozen data points at this time it seems the boots that Outlaw-X or Meidjo can’t maintain a grip on are mondo size 26 with a short NTN sole; unfortunately, too short. In all cases the toe-to-duckbutt length is shy of the specified length by half to a full millimeter beyond the tolerance limit.

It is hard to imagine Crispi changing their molds to cause this, but other factors could be at play to cause a shrinkage in the NTN sole length, from a change in material (a change in color can affect properties) to ambient conditions when the boots are injected.

There are also other dimensions that are relevant, like the thickness of the 2nd heel. Or, in the case of 2-pin NTN boots that work with bindings like Meidjo or Lynx, the position of tech inserts at the toe. According to anonymous sources at Dynafit, the axis of the insert cones should be 13.4 mm (+1.1/-0 mm) from the front of the toe. There is also a spec for the height above the plane of the boot sole, width of the cones, angle of the cones, etcetera.

The relevant dimensions for locating a tech insert in an alpine touring boot sole.  NTN boots follow the dimensions for AT boots at the toe.

The relevant dimensions for locating a tech insert in an alpine touring boot sole. NTN boots follow the dimensions for AT boots at the toe.

At the moment, there is no official specification for 2-pin NTN boots/bindings. Practically speaking it is a combination of the Dynafit insert spec and Rottefella’s NTN sole specification.

Solution

The solution is obvious, yet future. Building to specified dimensions may require some expertise, but it isn’t magic. Bindings need to account for boots exceeding their tolerances, and boots need to tighten theirs. In the meantime warranties may need to be exercised, or binding parts modified or replaced. Here’s hoping this only takes one season to ferret out.

Related Posts
Crispi NTN Boots out of spec?

Inserts: Weak link of the 2-pin System

CORRECTION:
The range of boot sizes that conform to a small NTN sole, or large, for Crispi boots was incorrectly stated. Crispi shells break on the half size like Scarpa (2X.5-2X.0), Scott shell break on the whole (2X.0-2X.5). First version had that backwards.

© 2019


  • Dan Ling

    That example picture looks off. It appears that the Crispi boot is slightly lower or angled. A better example would be to show it measured with calipers.