So I've had my first Shimano crank failure. It was on my gravel bike. The bonding between the main forging and the smaller c-cross-section insert along one edge of the left-hand crank failed, causing the hollow "torque tube" become structurally incomplete. The crank went flexy as a noodle, especially out of the saddle. I nursed it for 90km and had it replaced with a second-hand XTR crank to get me through to the end of our gravel bike-packing trip.
Now, my puny watts are unlikely to have caused the component any meaningful stress at all, so I'm surmising that it is the effect of standing on the pedals when descending rough roads that was the cause of the stress and ultimate failure. It was about 4 years old. My caution is that road components (even very good ones) might not be the best choice for gravel-biking due the different way they're stressed. Interested in others' experience.
Now, my puny watts are unlikely to have caused the component any meaningful stress at all, so I'm surmising that it is the effect of standing on the pedals when descending rough roads that was the cause of the stress and ultimate failure. It was about 4 years old. My caution is that road components (even very good ones) might not be the best choice for gravel-biking due the different way they're stressed. Interested in others' experience.