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I'm trying to get my head around this mess. The bit which fails first is the glue. It happens in older, heavily used cranksets. Maybe Shimano knows why, but they're not saying. It might be corrosion and/or the atmosphere at factories in far east climates.
i'm sure i read somewhere that part of the reason for the failure was due to water ingress through the unsealed hollow axle, which then causes internal corrosion.
seemingly part of the fix on newer hollowtech cranksets is that there is now a plastic bung in the axle.
don't know how much truth there is in any of that though...
i'll try and find a link.
bigshape-
Peak Torque video from 2020; in his opinion a combination of hot humid air being sealed in the cranks in the factory as parts are sandwiched together, then water condensing as cranks exposed to cold coupled with tiny gaps between sections as adhesive fails also causing capillary action and pulling surface moisture in making corrosion even worse.
dubtap
I'm trying to get my head around this mess. The bit which fails first is the glue. It happens in older, heavily used cranksets. Maybe Shimano knows why, but they're not saying. It might be corrosion and/or the atmosphere at factories in far east climates. After the glue comes unstuck the aluminium drive side arm has to bear a much higher load than it was designed for, so it gradually weakens and loosens and eventually snaps.
If Shimano says your crankset might be affected, but it hasn't snapped yet, you don't automatically get a replacement. First a bike shop is supposed to inspect it. We don't know what they're supposed to look for. Perhaps they give it a wiggle to see if the glue has failed? And perhaps Shimano believes that if the glue hasn't failed yet, it never will? Or it will fail in such small numbers that they don't care about the legal and reputational repercussions?
Lawyers and regulators think that every vulnerable crankset should be replaced. In other words, a full recall, as seen in other industries.
Shimano is being obstinate and arrogant and incurring the wrath of dealers and distributors. Could this go all the way to a humiliating climbdown and televised tearful apology from the big boss? It's still a family business. Four of the top people are Shimanos. The family owns 11% of the shares. Not the sort of thing associated with progressive corporate governance.
Shimano has 50% of the world's component business, and 70% of the high end. But the Covid boom is over. Component manufacturers' revenues for 2023 will be 25-30% down. The market is oversupplied. Disgruntled Shimano buyers have other options. Maybe this will be a turning point, with Shimano' s monopoly being slowly lost to the likes of L-Twoo.
Sources:
https://road.cc/content/feature/investigating-shimanos-snapping-cranksets-304173
https://road.cc/content/news/solicitors-view-shimano-cranks-roadcc-podcast-304479
https://seekingalpha.com/article/4572435-shimano-bike-component-monopoly-at-an-attractive-price
https://www.forbes.com/sites/carltonreid/2023/08/11/cycle-industrys-collapse-after-bike-boom-ends-this-year-say-analysts/?sh=7c3efbab66d9
https://road.cc/content/tech-news/budget-groupset-going-take-over-shimano-di2-300065