NOTE: See how I listed "confidence" and "know-how" as key must-haves for this job? This isn't a task for an amateur shade-tree mechanic with a crescent wrench and a big hammer. Do it wrong, and you can strip the bottom bracket threads right out of your frame, thus ruining it (and good luck making a warranty claim for "unskilled, overzealous home mechanic"). So it goes without saying that you should proceed at your own risk, and if things go wrong, you've learned a valuable lesson in not taking advice from the Interwebs.
With all those necessary disclaimers disclaimed, here's what to do:
- Remove the bottom bracket: As this is a senior-level course, I'll assume that you know to pull the cranks first, and that you have whatever tool your particular bottom bracket requires.
- Thoroughly clean the threads on the BB and frame. Get all the old gunk and grease out of there. It doesn't have to be operating-room clean, but the less mess in the interface, the better the chances of success.
- Wrap the BB threads with Teflon tape. It's the white, slippery (and thus, non-adhesive, duh) stuff commonly used by plumbers on threaded fittings. About two bucks should buy you a lifetime-supply roll from any decent hardware store.
- Reinstall the BB. And the cranks after that, duh again.
- Don't lose the threads: The tape can make it tough to discern where the threads are when you're making those first crucial turns into the frame, and the added thickness creates enough resistance to make it hard to tell "going in straight" from "cross-threaded." Proceed with caution.
- Remember your rightsy-tightsies and leftsy-loosies: When you're wrapping the Teflon tape, make sure you're winding it in the correct direction so it doesn't unwrap as you install the BB. The degree of difficulty goes up since the non-drive cup has right-hand threads and the drive-side cup has left-hand threads. Even I have to stand there with the cup in my hand, miming the installation and imagining which way the tape will twist, and I've done about a zillion of these things.
- It won't feel right. If you know how a bottom bracket is supposed to feel going in (and if you've made it past all the warnings so far, I hope you do), the extra resistance is nerve-wracking. Plus, you'll probably push some extra "strings" of tape out of the threads which can look disconcertingly like ribbbons of stripped metal. Do not panic.This is normal.
Why not just use grease? Well, you can, and it will work for a while, but grease doesn't seem to stay in place quite as well, so the creak comes back sooner. Something about the Teflon tape fills the gaps with a bit more permanence, and seems to provide a little more noise dampening at the same time.
So why do I call this the Cannondale Creak? Well, having worked for three different Cannondale dealers (and having owned four Cannondales of my own) over the years, I learned that if someone brought in a (relatively new) 'dale complaining of a creak, this was the fix 99 out of 100 times. I'm sure it afflicts plenty of other frames, but I'll always associate it (fair or not) with beer-can bikes from Bedford. Those gigantic aluminum downtubes are like megaphones, amplifying even the smallest (and most likely harmless) sounds. It's certainly not a value/quality judgement on a particular brand -- after all, the only reason this fix is fresh in my mind is because I just did it on the two (count 'em, TWO) bottom brackets on our Cannondale tandem, a bike that gets the "pry it from my cold, dead hands" seal of approval from captain and stoker alike.