A client brought in a bike with a clicking bottom bracket. On taking it for a test ride there sure was a clicking coming from the bottom bracket. Opening it up revealed that about half of the thread on the drive side had been stripped at some point so you might be forgiven for assuming this was the source of the clicking - especially as it had been fitted with Loctite. It doesn't look healthy, does it?
In reality, the source of the click was something much less sinister. The rear wheel quick release skewer wasn't tight enough. It was tight enough to stop the wheel falling out but not enough to stop slight movement in the frame when pressure was applied to the drivetrain. The click from the rear end was being transmitted through the chainstays making it sound like it was coming from the bottom bracket. Tightening the quick release skewer about half a turn fixed the problem. Whilst unusual, this isn't unheard of.
Other common sources of bottom bracket noise are:
- Non-drive side crank incorrectly fitted or not to torque (Hollowtech and similar)
- Unfaced or badly faced bottom bracket shell
- Pedals requiring servicing
- Badly worn or unlubricated bearings