BB backed out a few mm (probably from hitting a bunch of rocks in the uptech recently, usually pretty good about it but you know ) enough for my chain line to start dropping chain in the front while pushing my 3 lowest cogs in back. Sound plausible? Idk.
by fanclubmoss
5 Comments
If installed correctly that should be impossible.
Looks like it. A small drop of blue loctite would have kept it in.
So here’s my theory: the marks on the bb tell me someone may have tried to loosen and/or fasten it without the proper tool. I don’t see a scenario during riding that would scratch it so thoroughly, and evenly, without completely wrecking the bb housing too. not fastened properly, worked itself loose.
Keep an eye out for a bearing on its way out. Obviously it didn’t cause the marring, but BB threads are designed to remove themselves from the frame if seized. Maybe that compounded the issue.
It’s just unscrewed itself on the rock. Tighten it back up a good to go, but if you have it dismantled then just swap it out.