Went to replace my BB90 bottom bracket bearings on my Trek Checkpoint because they were 3 years old and creaking. Pulled the crankshaft, popped out the bearings and pulled the plastic sleeve out and found this little gravel pile in there. Only way I figure all this could get in was to get flicked up through the little drain hole at the front/bottom of the frame.
My previous bike had internal cable routing for a bottom pull Front Derailleur, but the routing didn't have internal sleeves. The hole for the FD cable popped out on the downtube just before the bottom braket. I ran 1x so I didn't use it.
After many miles of use, I needed to replace the BB. When I pulled my crank and unthreaded the old BB, the entire shell was completely packed with sand. Luckily the BB sleeve kept it out of the BB and crank spindle.
The bike also didn't have a drain hole in the bottom of the BB, which didn't help.
I put a piece of frame tape over the hole, which eliminated the issue going forward...
