I have had this sporadic creaking in the crank/ bottom bracket of my mountain bike. It makes said noise several times every revolution. I have brought the bike into several shops, but they have been able to do nothing. I have heard the theory that since it is an aluminum frame, it is just the bike flexing. The one thing I have noticed is that the noise stops when I ride in wet conditions. I have replaced the bottom bracket and everything is as tight as can be. Any suggestions?

I know you dont want to hear this, but inspect very carefully the area around the intersection of the bottom beacket, down, and seat tubes for a small crack in your frame.
This sounds like a very likely possibality.

Steve.

The other possibility is loose chainring bolts. Bicycling Magazine had an article on that last year.

I will add to the other things mentioned as things to look for. Other causes of this is aluminum vs. steel. The two metals have different expansion rates and when they do this "creaking" has been known to occur. Very common with alu. frames. Another possibility is the crank arms need a little grease on them when you put them on the b.b. spindle. Another possibility is the threads on your pedals need grease when screwing them into the crank arms. Another possibility is the threads on the b.b. cups need grease when installing it into the b.b. shell. Other than the above mentioned checks that is all I can offer.

The sound may be coming/transmitted from somehere else, strange but true. Try checking bolts, nuts, clamps etc elswhere on the bike.
Do not grease your crankarms, (as mentioned above), where they interface the spindles. More than one manufacturer requires that those surfaces be CLEAN and DRY, even cleaning with acetone is recomended to remove ALL grease and other comtaninants!!!!
If you grease the spindle flats it is very likely and easy to overtighten the crankarm. I learned this when I was working for one of the best and most respected shops in the nation, we used to get calls from customers from all over the world!
If the BB is a Shimano sealed bearing unit, they they have in the past, recommended the putting silicone seal on the BB or cup threads.

If you are lucky, it is your pedals or one of your pedals. This is pretty common.

If it is not your pedals, then a crack in the aluminum frame would be a good guess - especially if the creak is more than a short "tweet".

Aluminum has always been prone to breakage which is one of the reasons it's popularity has been minimal until recently; despite earlier experiments with aluminum frames in the 1930's.

Steele-Bike, I was biking with a friend of mine this weekend and we experienced the same creaking you explained.

Turns out, the problem was in the connection of the crank arm to the axle.

It seemed tight, but it still creaked. I isolated the trouble by grabbing both crank arms and simultaneously pulling them both up and pushing them down. The exact crank was identified by pedaling only one crank at a time.

I removed the crank arm, cleaned off the crank arm, axle, and cotter (ya, it was an older bike), put a touch of grease on the cotter, and counter-sunk it in with a punch and hammer.

That worked.

Did you ever find the cause of your troubles?

I have two old bikes which were originally made with cottered cranks. I took them off immediately and never rode them. I kinda regret that, at least on one of them, because it's classy looking.

What kind of pedal system do you use? It might be your your cleat rubbing against the pedal, mine does the same sometimes.
Since it stops in the rain, the water may be acting as a lubricant between the pedal and the cleat.

S-B
Is this the same bike that is having the chainslip problem?… If so, could be that #2 chainring giving you the problem?

That's my shot in the dark.

Here is another revelation from the latest tour I went on. My friend has a squawk that drove him nuts. As you noticed, his squeeking also went away when the bike got wet (rain).

After a lot of searching, it was found that the culprit was the crank arm connection to the BB axle.

It's worth a check.

By the way, this post is pretty old already. Did you find the source of the problem?

I have since fixed the creaking. It ended up being at the seat/seat post area. Just a little tightening and all was fixed. This is a different bike than the one that has the chain slip.

The bike that had the crank problem with has now started creaking on the pedal. I am assuming it is the cleat rubbing against the pedal. I have heard this can be fixed by applying paraffin wax on the cleat and/or pedal, but I have yet to try this.

Oh, for God's sakes!

That's what I said. I had taken the bike in to a couple of shops and they never figured it out. They just wanted to sell me a new BB. My new motto is....if something is making a noise, don't assume it is coming from where it sounds like.

Just to throw in a couple of more possibilities, even though the issue in this particular case has been resolved.

I had a squeak a couple of months ago that drove me nuts for a few days until I figured out that it was the edge of my shoe lightly brushing the zip tie that holds the cadence pickup magnet to my crank arm. Moved the cleat over about 1 mm and squeak solved.

Another tip I read just last week was spray a little silicon lubricant on your shoe sole in the area under your cleat (primarily Look and similar cleats). Slight flexing of the sole can cause a squeak against the cleat. This is one that could also be affected in the rain since a little water in there would also provide some lubrication for a while.

FWIW,
Raymond

This is a good lesson for everybody. You know, problems never seem to be where you first think.

Recently I was on a ride with a guy who had a maddening clicking sound from his BB with each revolution of the crank. I tightened the BB (not a fun rode-side project with simple tools). Still, the problem existed. Come to find out, it was the bolts of his front sprocket banging into the mounting of his kick-stand. I took the kick stand off and problem was solved, "You won't be needing this anymore, Bud. Heave HO!!"

This week I had a strange sound coming from what appeared to be my front brake rubbing against my rim. The rim was true and brakes calibrated correctly. What the heck?! I checked and checked and adjusted. It drove me nuts. Sure enough, it was problems from the REAR brake.

That is the art of being a good bike mechanic. Anybody can do the maintanance. The bike mechanic artisto can isolate and fix problems fast.

This is where I fall into the spectrum. I can do the maintanance, just not all that quickly.

I do not know many people who cycle, so any thing I know about bikes is mostly self taught. I was the kid who sat out in the garage tearing the bike to pieces. I couldn't always get it back together, but I sure knew how it came apart.

Man can I relate to that. My parents still razz me about the time I took ALL the knobs off the doors in the house! (It just gets curiouser and curiouser.) Point being, you are not alone in the time honored tradition of taking things apart, putting them sorta back together, (and having a few extra screws, nuts, bolts, etc. left over!!) :( Ah, well, it's ONE way of doing it! :)

Pass the torch of knowledge, boys. It is a treasure. The techniques you learn on your own could be superior to other typical methods.