Dynafit ZZero is still one of the lightest 'stiff' boots out there for backcountry skiing. Why this boot does not include cuff alignment feature is a mystery akin the location of Atlantis. Rivet to be replaced is indicated by arrow.
For our project, we used a cuff alignment fastener set (screw rivet) from Scarpa. You have to hand it to Scarpa, they're always ahead of the game on this sort of thing. For example, almost all fasteners on their boots are threaded and easily removed for repairs or mods. In the case of this Dynafit boot, we'll be removing the fastener with surgical precision using a nice sharp drill bit.
First step with removing OEM rivet is to drill a centered pilot hole. Cool with water from a spray bottle, otherwise the heat from drilling will damage surrounding plastic
After you've got a pilot hole, drill slowly with a larger bit till the rivet head pops off. You'll need the red washer, but will be enlarging the hole in the washer so a bit of damage to the washer is ok. Just be sure you don't drill into the boot plastic while removing the rivet.
Drill out red washer with step bit so it fits the neck on the inside of the external portion of the screw rivet.
Ready. Also, the hole in the boot cuff is drilled with the step bit to enlarge for the exernal portion of the cant fastener.
Next, the most challenging part of the process. Install internal portion of screw rivet by heating and melting into the boot shell. Hold the part using a metric bolt inserted and locked with a nut. WARNING, if you overheat this part you run the risk of punching it right through your boot shell -- a difficult mistake to repair. THIS PROCESS DOES NOT REQUIRE MUCH HEAT. Trick is to test on a scrap of boot plastic from a dumpster boot or something like that, and have an assistant quickly spray with water once the metal has bedded slightly deeper than internal surface of boot cuff. If you don't have a test boot, you can do small melt tests on the inside of the plastic where the buckles attach.
Testing temperature of fitting on throw-away plastic.
Internal fastener T-nut is held with a bolt, nut, and vise-grips. Super tricky. Practice first.
One problem with using the Scarpa fasteners is that the machine screw is slightly too short for the added thickness of the ZZero cuff (due to washer and carbon fiber stringer). Best solution is probably to make another fastener by cutting a hardware store flat-head screw to length, but the stock screw does work if you make sure the internal fastener is bedded as deeply as possible without melting it through the boot.
CRITICAL, once you've got everything put back together and the cant angle set where you want it, it's essential to 'lock' the machine screw by peening the end as well as installing with Loctite. Peening is done on the interior of the boot, using a pointed puch cut to length so it fits inside the boot on a chunk of steel, while you tap on the outside head of the screw. Scarpa screw has a nice configuration on the end that makes it easy to peen. If you cut a custom screw, peening may not do much. In that case, do the final install of the screw using JB-weld as thread locker. Don't be afraid to tighten everything firmly.
Mod completed, cuff alignment fastener installed in Dynafit ZZero backcountry skiing boot.
– When you obtain the cuff alignment fasteners, get two sets and keep one set in your repair kit in case your install comes lose in the field and you loose parts. By the same token, be sure you’ve got the tools in your repair kit to tighten the cuff fastener.
– We’re not sure how will stocked Scarpa is with their cuff rivets, nor how willing they are to part with them. If you have trouble with sourcing, another way to get cuff alignment parts is from dumpster boots.
– Practice the melt-bedding of the internal fastener on junk parts or boots.
– Know this project has a WildSnow wrench level of about 8 on scale of 1-10. You’ll need a well equipped shop as well as well developed hand-skills.
– See our previous post about doing this same project on a pair of Garmont Masterlite backcountry skiing boots.