Video: Pre-Season Testing & Data Acquisition with Lewis Buchanan in Lousa

 For reference, here’s my previous comments-section engineering analysis of Thibaut’s Snowshoe Enve rim failure videos, from September:

Those rim pings and pops from the previous rock garden (and his relative sketchiness steering through that section) were most likely the rim cracking and delaminating ply-by-ply, prior to catastrophic failure during the crash. As the plies fail, spoke tension will decrease and steering precision will likewise decrease. Composites will often fail sequentially, ply by ply, audibly (as often heard when structurally testing composite structures / components to failure) — until the structure gives up and fails completely, usually in spectacular explosive fashion. In the video from blowmyfuse, you can hear the wheel cracking through the last several plies as he hits the last few bumps before it fully implodes. In my expert opinion, based on detailed observations of about a dozen ENVE wheels, ENVE introduces structural flaws into their wheels at the spoke holes — and they do this by molding-in the spoke holes (at least this was the case in past years, and I believe they still do that molded-in process). The hole-molding dowels they use (or used) spread the uncured prepreg fibers around the dowel, creating small resin-rich regions in each ply around the dowel where the fibers spread. They should mold the rims whole like We Are One and then drill the spoke holes after. That will prevent microcracks from forming in the relatively brittle epoxy resin-rich pockets that ENVE tends to create in each ply around the spoke holes. Those microcracks can turn into larger cracks that can form large delaminations between plies, or inter-ply transverse cracks through the thickness of the laminate. Cyclical loading like that is just about the worst thing for microcracks around a resin-rich hole in a composite structure. As those epoxy-resin microcracks get larger, the compressive forces on the carbon fibers increase — and carbon fibers usually fail in compression rather than tension. When the carbon fibers fail, you’ll hear them “pop” ply by ply before a big final compressive + tensile catastrophic failure of the remaining composite plies in the structure. Anyone who knows composites well knows that holes, especially spoke holes, are generally a bad idea in composites (as such, many companies create engineering / design / materials work-arounds to seriously increase the strength of the area around spoke holes in carbon fiber rims). ENVE’s molded-in approach is particularly risky, in my opinion, particularly with how the spokes introduce cyclical loading, spread over a very small surface area, right at the spoke hole...creating a huge gradient of tensile and compressive stresses on the resin and fiber, through the thickness of the laminate, right around the spoke hole. This is a recipe for failure, especially with the crack-prone resin-rich regions in the plies on ENVE’s wheels. I’ve seen ENVEs crack and split at the spoke holes just from wheel building (right along the center line of the rim, initiating from the resin-rich flaws introduced by their spoke-hole-molding dowels). Considering this, it’s not surprising that Thibaut’s rim ultimately broke in several places, right at the spoke holes. The sort of failure we witnessed most likely indicates a structural flaw / cracking at the spoke holes, more than it indicates a flat tire rim failure from compressive impact to the outer rim edge. Also, Thibaut’s rear wheel appears to be cracked (or a decal is coming off), as seen when he is sitting after the crash...but it looks like a crack / delaminating ply, as it starts at the spoke hole and extends toward the rim edge at a 45-degree angle, consistent with their ply orientation.