Part Five in a week of Dynafit. Without you esteemed blogsters commenting on it, I never would have realized that all these years I’ve been setting my Dynafit release somewhat by instinct. I’ve always been certain how the horizontal release scale worked, but for the vertical numbers I’d just assumed the tiny raised plastic hatch marks (ridges) were somehow a scale of 5 to 10, and that the big printed numbers were there to call attention to how the hatch marks were scaled.
Then I looked at the binding and thought about it. Sometimes that’s dangerous. The thinking, anyway. The more I looked, the more confused I got. So I contacted my sources this morning. Yep, the hatch marks are the settings, the big printed numbers just indicate the range of the marks. Check out the photos.
For ultimate safety, it’s useful to adjust vertical and lateral release values independent of each other. In other words, use a chart to figure out your DIN number, then set your bindings perhaps one number below that. Ski the bindings. If you have an unnecessary release (prerelease) just dial up the binding for whatever mode that release was in (vertical or lateral) and leave the other setting alone. I’ve found that I can leave my Dynafit lateral setting quite low, but need to keep the vertical setting at or slightly above what the DIN chart recommends. For extreme skiing when loosing a ski could kill me, I dial everything up 2 or 3 DIN numbers above my usual, and when on the actual danger terrain I use the touring lock which blocks lateral release up to around DIN 15/18 or so my sources say.
One other thing about adjustments: The space between your boot heel and binding is CRITICAL. It’s 4 mm for TLT models, 6 mm for Comfort/TLT/ST. BUT, do not set this by trying to use a ruler, you must use the feeler gauge included with the binding. See our Dynafit binding FAQ and other articles for more about this.
All this leads to one of the more cryptic bits of Dynafit trivia. What do the “MY” and “MZ” printed on the side of the binding mean? They obviously attempt to communicate which is the vertical release scale and which is the lateral. But, is this some sort of insider Tyrolean engineering thing or what?
So, I emailed Fritz Barthel, inventor of Dynafit bindings. Here is what Mr. Barthel says the origin of the terms is:
This derives from the (cartesic) coordinate system for a boot-binding-ski system that is used in the ISO standards. The z-direction of this coordinate system is pointing “upwards” (direction of the shin bone ) therefore a torque (rotation) around this Z axis applied to the boot is the torque needed for lateral release. The Y direction is “sideways.” A torque around this axis applied to the boot would open the binding in vertical direction.
Thus, “Mz” = momentum (torque) around the z-axis, “My” = momentum (torque) around the y-axis.
(Editor’s note: The confusing aspect of this is that while the Z axis is vertical and the Y horizontal, the marks on the binding end up being the opposite, with MZ meaning lateral release (because this actually means rotation around the vertical axis, and so forth for MY.)
In the standards the release values are defined as torque (and also measured by the TÜV with devices that apply “torque,” also for front release.) E.g., a setting of “8″ for the lateral release would mean that a torque of 80 Nm on the boot should open the binding (plus/minus some tolerance). The “forces” to hold the boot then depend on the “lever,” in this case the boot.
That’s why the tables in the manuals compensate for the length of the boot changing the torque. The standard settings end with “10,” everything beyond that value is not covered by a standard. “10″ means 100 Nm, which is the equivalent of a bucket of water hanging on a lever with a length of one meter. Imagine you hold your foot horizontally, the lever is attached to the boot and you try to lift the bucket of water through rotating your leg. “20″ would mean 200 Nm, nobody is able to open such a binding statically (in slow motion).