Not the 02's but........
by Lou Dawson
All randonee bindings allow more boot movement than good quality alpine bindings. Some skiers find this to be a trivial issue -- others take it seriously. The "one-rig" breed of randonnee bindings, comprising the Fritschi Freeride and Naxo NX01 and Naxo NX21, are the bindings most often taken to task on this issue. Yet all bindings wobble and bob, with the Naxo NX01 having slightly more movement than the Freeride (the Naxo NX21 has virtually the same stability as the Freeride. If you like the Naxo's features, but want it to equal the lateral stability of the Freeride, here is a modification that makes makes the 04/05 model Naxo NX01 equal to the Freeride.
Naxo binding with Torque Plate installed for an approximately 6% increase in torque resistance.
Torque Plate being inserted in rear of Naxo plate reails, notice rabbits milled on sides of plate, creating flanges that fit in rail slots.
When we bench tested the deflection of both bindings, I noticed that both allowed quite a bit of movement at the toe and heel, but the Naxo NX01 plate appeared to torque more, presumably due to it being two small bars arranged side-by-side and easily twisted, probably due to their having an open slote on the inside, rather than being a closed tube. It seemed that manufacturing a plate that inserted between the bars could stiffen them significantly, so we did just that.
We started with 1" x 1/4" hardware store aluminum bar stock. Using a router with a cutting guide and straight cutter, we milled two shelves (known as "rabbits" in some trades) in the sides of the stock so it would slide tightly between the Naxo plate rails, with the milled side flanges fitting the existing slots on the inside of the binding rails. We then cut the milled stock to length so it would fit in the gap between the Naxo to and heel units, once the binding was adjusted for boot length. To insert the plate, we removed the binding plate end-cap and slide the heel unit of the rails -- an easy process that only took moments. The whole project took about three hours.
Detail of custom built Torque Plate.
We measured the results using a side-by-side comparo and test rig, and found the plate beefed the Naxo to equal the torque resistance of the Fritschi Freeride.
We test randonnee backcountry skiing bindings for how solid they attach your foot to the ski (as when the cuff of the boot is tilted/pushed from side to side). While this is not as big a factor in control as some people think, it still makes a difference in how the binding “feels,” and definitely affects how well bindings ski on hard snow or ice, especially if your skis tend to flutter or chatter, and you need a binding that doesn’t exacerbate that effect.
For this evaluation I use essentially the same test rig as in my preliminary test done a while back. With the general procedure the same as detailed here, though we’re now a bit more careful, and made sure our results repeat. Results below use dashed lines as horizontal bar graph, each dash for one unit of deflection. A “unit” is simply arbitrary and only a basis for comparison, it is not a defined measure of weight or force. What I found fascinating is that the Freeride and heavy duty Naxo Nx21 (formerly known as the “Stomp”) were essentially equal to the Marker alpine binding, while the Dynafit was quite a bit more solid than anything but the Duke, even though it appears incredibly minimal. Shows you what good design can do.
Marker Duke
——————– (19 units deflection from vertical*)
Dynafit
——————– (20 units deflection from vertical)
Fritschi Freeride Plus (2006 model with black toe wings and red support plate under binding)
————————– (26 units deflection…)
Fritschi Freeride (2004 model with white toe wings)
————————— (27 units deflection…)
Marker M1100 Titanium alpine binding
—————————- (28 units deflection…)
Naxo Nx21
—————————– (29 units deflection…)
Silvretta Pure Freeride
———————————– (35 units deflection, measured virtually the same as other Pure models)
Silvretta Pure Performance
———————————— (36 units deflection, 07/08 model has solid carbon rails instead of hollow, should be slightly stiffer)
Naxo NX01
——————————————- (45 units deflection…)
*Marker Duke, when used with alpine boots could possibly be somewhat stiffer than measured here, as we used Dynafit compatible randonnee boots for all tests, and the sole of most such boots does twist more than a quality alpine boot. More, the base support of Duke is wider than any binding, and is said to thus give better edge control on wider skis. We don’t know if that’s true or not, but it sounds worth considering and could mean the real-life feel of the Duke is more solid than our chart indicates.
Due to inherent error in any mechanical testing system, I’m confident in saying the Marker alpine, Freeride and Naxo Nx21 bindings are all essentially equal in lateral twisting stiffness, while the Pure and Naxo NXO1 are clearly much looser. Marker and Dynafit are the clear winners overall — stiffer than the alpine binding and the Freeride!
The “units” above are for comparison only, they have no direct relationship to any unit of distance or weight. My gut tells me a difference of under 4 units would only be noticeable to precision skiers who could switch skis during the same run while using the same boots.
An interesting aspect of this study is the realization that if you use bindings with less flex, you might be able to use a more moderate boot and get the same performance as with a stiffer boot and flexy binding. All you stiff boot lovers might want to keep that in mind when considering Dynafit.
