Found a cracked bottom bracket shell on a 90s Trek

I was stripping down an old 930 frame last month at my shop in Portland and found a hairline crack running along the bottom bracket shell. Turns out the previous owner had been riding it with a loose crank arm for years, which must have flexed the shell just enough. Has anyone else seen this kind of crack from loose cranks, or is this a rare one?

2 comments

2 Comments

michaeladams2d ago

Used to think those cracks were just bad luck but this totally explains some failures I have seen.

val_taylor2d ago

Totally agree @michaeladams, I thought I was just unlucky with how some of my builds held up over time. Then I took a closer look and realized the same kind of cracking was happening right along the grain. It's like a lightbulb went off once I saw the pattern.