From a quick google-bash it seems that this issue is only being flagged on Ultegra and Dura-Ace cranks; t
his poor bloke has had one of each fail; the second being a replacement for the first. He probably had some time to calm down before writing his blog entry, but had that been me I'd have lost my sh*t on the second one and being in the litigous US would be slinging around suggestions of legal action as there's clearly an issue with these products that presents a clear and potentially very serious safety risk to their riders.
Trapped moisture in voids during manufacture leading to thermal cycling and failure of adhesive/meniscus. Suggestion that the ?vast majority of failures have been experienced between latitudes 30 north and south (Tropics of Cancer and Capricorn plus a bit).
Interesting observation. Certainly looks like it's a problem with the bonding; being a luddite I was a bit disappointed to see that this much-touted "Hollowtech" format relies on bits being glued together.
Having just bought a bike with a 105 R7000 groupset I'm relieved that I can't find any examples of such failures on these cranks, although they are a bit newer so have had less time for the problem to occur.. and while being heavier I imagine the assembly process and bonding agents used are probably the same as those in the two higher-end groupsets.
Not what I expect from Shimano tbh; one of the few manufacturers in this industry that I have (had) pretty much 100% faith in / respect for
It seems that knowledge of these issues is gaining momentum and it'll be interesting to see how the manufacturers handle it.
