by
Lou Dawson
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| Home brew test rig to evaluate binding
stability. 03/04 Freeride to left, 04/05 Naxo NX01 at right.
Rig uses lever arm projecting from boot top, with older rando
boot as weight. Skis are firmly clamped to bench. |
As Randonnée
bindings become more alpine-like in look and performance, it's
inevitable that the way they hold your foot to the ski will become
an issue. This is especially true of the Naxo and Freeride plate
bindings, two offerings that compete to be the "one-rig" setup
of choice that can perform both at the ski resort and while backcountry
climbing.
Scientific testing of Naxo and
Fritschi binding slop and foot retention is difficult.
Most factors can be equalized, but adjustment of the toe jaws
up and down makes a significant difference in boot movement --
and there is no exact way to set a perfect toe jaw height as
boot rubber compresses and plastic flexes. More, the heel release
tension (vertical release) setting may influence lateral boot
deflection, as the boot heel tilting during torque will tend
to lift the heel jaw. Thus, even the vertical release DIN needs
to be exactly the same for perfect comparative testing, and simply
setting it by the number on the binding is not accurate enough
-- it would need to be set according to a measuring machine.
Adding to the confusion,
the shorter the Naxo or Freeride plate is in relation to your
boot, the less it will torque. But because the two bindings
come in sizes that have varied relationships to boot length,
certain boot lengths might do better in the Naxo; others in the
Freeride.
All that said, a seat-of-pants
comparison of Naxo and Freeride is possible. One can simply
place two skis side-by-side, snap the same size boot in either
binding, with the same DIN and best toe-jaw height adjustment
possible, then wriggle the boots. Beyond that, one could clamp
both skis to a bench, and rig up a crude measuring device to
reach some sort of repeatable comparison between the two bindings.
Recently, I spent
some quality time in my shop, and did both types of tests.
It was an interesting project.
First, let me be clear that both bindings have quite a bit more
movement than a good quality alpine binding. Yet truth be told,
it's surprising how much slop their is in an alpine rig as well.
Check one for yourself.
Starting the test
For the tests described here II used the same "size" bindings,
a medium 04/05 Naxo NX01and a standard Freeride of '04 vintage
(as far as I know, the beef of last year's Freeride is the same
as this year's, so for comparison it worked fine). Length (size)
of the binding is important because the longer the binding
plate, the more it will twist and deflect under load. Thus, using
the shortest binding size possible for a given boot is the way
to go. In my test case, neither the short size Naxo nor Freeride
would have fit my test boots -- so my comparison is realistic.
In real life when buying bindings, be sure to
compare and see how short you can go. If you discover that the
shorter size of one of the bindings will fit your boot, use that
as part of your buying decision -- it will be lighter and torque
less, and possibly be more durable since the shorter plate may
place less leverage on associated binding parts.
Bias
l received complimentary
bindings from the suppliers of both products, and receive equal
product support from both companies, so my "swag bias" is
equal. More, I don't favor either binding as a one-rig solution.
They both worked well during my field tests, and frankly, both
ski downhill fine for my style (less aggressive but precise
and smooth, with occasional bursts of as much power as a middle
aged and fit recreational skier can muster).
Seat of the pants
Both the bindings were mounted on skis of similar width and flex,
and fixed securely to my solid workbench using steel bars
and clamps. I used the same boot for all tests, a Garmont Mega
Ride that I kept buckled the same. I adjusted both bindings
to the same DIN number (7), and did the best job I could on
the toe jaw height setting, with my goal to adjust the bindings
as similar to each other as possible, while doing it in such
as way that stayed with manufacturer's specifications and instructions.
I then simply clamped the Garmont
boot in the binding and wriggled it side to side in a way that
tilted it left/right. First impression was that BOTH bindings
had quite a bit of movement. The Freeride toe jaw could be seen
wriggling and rocking under the head of the height adjustment
screw, and the whole binding could be seen twisting, and when
the boot was tilted hard to the side, the tilting of the heel
would lift up the binding heel unit. The Naxo NX01 had similar
movement that was easier to induce. The NX01
toe jaw could be seen flexing, the plate could easily be seen
twisting, and the tilting of the boot lifted the heel unit.
More precision
Again, while I could feel the Naxo was easier to move,
the difference was too small to allow any accurate assement.
Thus, I needed something that approximated a more scientific
approach. To that end, I built a test lever consisting of a
vertical steel post and attached horizontal lever arm. I buckled
the post in the boot, and weighted the arm with the same amount
for each test. To quantify, I simply measured the difference
in deflection of the vertical arm while weighting and un-weighting
the contraption. The process was a bit crude, but the results
were repeatable (a prime qualification for any worthwhile test).
Results
First, let me say that a better test would graph resistance through
a range of motion, rather than static deflection. Thus, my
test was only a crude and preliminary read on binding deflection.
Nonetheless, the numbers reflect my "feel" test.
With what I thought to be reasonable torque for testing (yielding
quite a bit of movement, but not yanking the boot out of the
binding), deflection of my vertical lever on the Fritschi was
about 1/3 less than that
of the Naxo NX01.
Noticeable on the bench, yes. Noticeable on the ski slopes?
Perhaps. Cause for concern? Depends on your style of skiing,
what type of skis you use, and what type of snow you ski on.
Field testing
bears this out. Expert skiers testify that while they can sometimes
feel a difference between the Naxo NX01 and Freeride in terms
of slop, the difference rarely, if ever, affects their skiing.
With wide skis on hard snow, the difference may be noticeable.
On packed powder and most natural snow (crud or powder), the
difference means nearly nothing. More, if flex
is a huge issue for you, consider the Dynafit, which in the same
tests was more solid than any other randonnee binding.
(Caveat: An
interesting thing we learned during this test was that boot movement
can be significantly reduced by over-tightening the toe jaws
and moving them down past manufacturer's specified range. DO
NOT DO THIS. Over-tightening
the toe jaws of any Fritschi or Naxo binding model may result
in catastrophic failure. Such failures have been reported with
both Freeride and Naxo, and we suspect at least some of these
failures may be the result of mal-adjusted bindings. More, when
comparing the bindings yourself, take care that the toes are
adjusted correctly. After a day of playing with these issues
in the workshop, we suspect that radical differences in boot
movement sometimes reported may be the result of mal-adjusted
bindings during casual comparative tests in ski shops.)
And lastly, if you really do
want a Naxo NX01that's stiffer, here
is a way to modify it so it
provides about the same lateral stability as a Freeride or NX21.
[Wildsnow.com
Gear Review Policy]
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