Dynafit Anti-Twist Device, installed to left, shown apart to right. Click all images to enlarge.
We start covering anti-twist solutions for tech binding heels, and look what ends up on the front porch: Dynafit’s “original equipment manufacturer” (OEM) solution to the less than perfect anti-rotation of their Speed Radical binding heel. (In case you live in a bergschrund: Tech binding heels are usually designed with rotation to effect sideways safety release. This sometimes results in the heel unit rotating accidentally while in touring mode. Various solutions are directed at this problem, the best being hardware ‘stops’ that 100% block rotation.)
This add-on is part# 48870 Speed Radical Anti-Twist Device. Ostensibly available from customer service or through dealers. It looks simple, but is a little tricky to install properly. You have to use the included slightly longer screws, and be sure to flatten any “volcanoes” on your screw holes as the including washers need to sit perfectly flat on your ski. Clean everything well so no small bits of glue or dirt shim up the washers accidentally. Carefully epoxy and tighten screws that are going in for the second time as stripping screw threads in this situation is all too easy.
What you get: Device, washers (spacers), slightly longer screws.
Anti-Twist installed, with binding in touring position showing how it’s physically blocked from further counter-clockwise rotation. Incidentally, that add-on cap attached to the heel lifter is a B&D Nubbin lift extender. I use those because I shim up my binding toes for less ramp, and thus end up with less heel lift.
Looking underneath, Anti-Twist fits over the spindle base. We used double-sided tape between the device and the spindle base to take up some space as well as make the install go easier by holding things together.
The work went smoothly, everything is nicely thought out.
Mockup of how things end up sitting on ski. The washers act as spacers to compensate for the new layer of metal under the spindle base.
IMPORTANT! Screw hole volcanoes must be shaved to perfectly match flat top surface of ski, otherwise the washers get shimmed up too high and your installation will have slop. Epoxy the new screws and tighten carefully to not strip the screw holes. And as the Dynafit instructions emphasize, use the new screws!
I found that placing double sided tape between spindle base and the Anti-Twist makes the install easier, and takes up some space that was creating a small amount of play. Use thin tape, not thick carpet tape, as the thickness of the washers/spacers closely matches that of the Anti-Rotation plate that sits under the binding spindle base.
As viewed from above, the small plastic stopper appears functional and nicely designed.
Just to be clear, another expository view.
Dynafit Anti-Twist is Art: 48870.
Weight of one Speed Radical Anti-Twist Device (including slightly more weight from longer screws): 16 grams.
Added height of heel unit above ski (thickness of washers/spacers): 1.0 millimeter
Could this device be built into the binding base? Yes, doing so would be beautiful. Let’s lay some odds on who will do it first, Dynafit or the after-market?
Check out the Maruelli Antitwist for Speed Radical, it works on the same concept but has interesting differences.