I have a Trek 3900 Mountain bike that had a serious creaking problem whenever I would pedal. I found that the ring that holds the Shimano sealed bearing was really loose. I tightened it up and it helped somewhat. It loosened up again and I put loktite on the threads and really tightened it up but it is still creaking a little. The bearing cartridge seems fine. Any ideas?
Creaks are notoriously difficult to diagnose. Because a bicycle is constructed from tubes, sounds often travel through the tube and sound like they are coming from a completely different place than where they actually originated.
The following are, in more or less descending order, the most common causes of creaks that sound like they're coming from the bottom bracket. As you run through the list, take each bolt and/or part off; clean it, re-grease it, and tighten it back up.
Bottom bracket tightness. Check both sides. If you have access to a torque wrench, use it.
Crank bolts. You probably had to take the crank off to get to the bottom bracket.
Pedals. Make sure that they're bolted on tight. Make sure that there's no play on the pedal axles.
The bolt that clamps your front derailleur on. The derailleur can creak when the frame flexes if it's not tight.
Seatpost and clamp. The seatpost moving inside the seat tube can cause a creak that sounds like it's coming from the BB. Take it out, clean it, grease it, put it back. The seatpost rails can also creak where they attach to the seatpost or where the go into the seat. That sound won't usually travel to the bottom bracket, but anything's possible.
If none of that does the trick, work your way outward from the bottom bracket checking every single bolt on the bike. It could really be just about anything. Creaks can be very frustrating.
The ever helpful Sheldon Brown has a good article on diagnosing and fixing creaks.
Take the shell off of each side of that bottom bracket and grease each one up, along with the spindle. When you tighten that bottom bracket back on, don't over torque it or under torque it, if you over torque or under torque that bad boy is going to squeak. If you aren't sure of the torque or you don't have a torque wrench, visit your local shop.
Take the shell off of each side of that bottom bracket and grease each one up, along with the spindle.