There is a long story here, but ulitmately I am really disappointed in what I thought was a great product before today. I have a warrenty claim into Shimano and this will likely be covered, but I don’t know if I want another one of these on my bike. Some research shows that this is not that uncommon for people to experience this with the hollow tech cranks.
Am I over-reacting? Anybody else have this problem? Just slap on another and keep pedaling?
I don’t think so. Such a failure could cause a serious accident and just shouldn’t happen — unless you have had an accident or so. To me that is akin to a frame, fork crown, steerer or handlebars fracturing. Shimano should replace this under warranty.
On another forum I frequent, an avid amateur racer has had this happen twice with DuraAce cranks. Anecdotes ≠ evidence, I know.
Sometimes stuff breaks. And Shimano probably sells more cranks than anyone else, perhaps more cranks than everyone else combined. As long as they sort you out with your warranty claim I’d just get on with life.
Corrosion gets under that joint and delaminates the outer part from the core of the spider. It’s not the brightest design, in my mind.
I’m on my 3rd Ultegra hollowtech in 4 years. With my current one, I’ve gotten more rigorous about breaking down the crank once a month and greasing at those joins to keep corrosion from penetrating. I hadn’t thought to attempt a warranty claim.
Meanwhile the “is never get carbon cranks they can break” philosophy is still widespread. Really if you consider how much force goes through the cranks, it’s understandable how they can break. Hell I’m surprised chains can hold together as well as they do under sprints. Cranks also have some flex so it’s not out of the question that they can fatigue over time.
Just happened to me yesterday (R8000). My pedal started to vibrate so I slowed down right before it fractured. I was very lucky not to crash. Just past two years so I’ll see if Shimano covers the replacement.
Personally I have seen a few HollowTech cranks crack or separate, just like the ones posted above. Shimano are really good at covering them and I’ve even had out of warranty items replaced.
Should you be concerned? Only if you want to be. Yes it cracked but so can a lot of things and there are far more cranks in one piece. Don’t stress it, only change it if Shimano refuse to.
I hope you did not get hurt when “separation” happened.
That seems to be a systemic issue with Shimano’s current-gen Hollowtech cranks. Search for Peak Torque Shimano cranks on Youtube. He is an engineer and explains the underlying problem with the construction.