No, it's probably a crankbolt with an integrated dustcap. They're great, if you have a hollow spindle BB it's totaly worth replacing your old 14mm bolts with 8mm allen head bolts with dust cover. No more having to take out teh dust cover, no more having to worry about having a 14mm socket that isn't going to strip the bolt head. It's pretty great.

Here it is installed:

http://www.parktool.com/images/repair_help/crank107.jpg

and here's one so you can see what it looks like out:

http://www.cleanbikes.co.uk/PARTS/Pi...Crank_Bolt.jpg

Cool...keeps the water out too, I have found some rust inside my caps from riding in the rain and have clean them several time in the past 2 month as a result, I never had a problem stripping the 14mm bolts though.

I don't have the appropriate crank bolt socket, so I use a standard Ace socket set. The socket is tall enough that when torqueing up the bolt with it's shallow head, it's easy for it to slip off. I really have to work to keep the socket square to the head. It's much easier to have allen heads. Plus then I can just carry my multitool and have everything I need to tighten up the bolt in the field. Getting out 5 or 6 miles towards the trailhead on your 52" singlespeed mtb and feeling the left side crank start to flop all over is a good way to learn that lesson. "Hmm... do I gingerly pedal all the way home and hope I don't trash the crank or do I walk the whole way? Decisions, decisions."

When I first installed my cranks I greased the crankbolts and found that after a week a fixed/no brake riding that one side was loosening, so I tookem' out degreased the inside bb threads and bolt and used some blue loctite and torqued to spec., never loosened up again and I have disassembled it a couple times for cleaning without any problem (no seizing or anything). with all the salt that has been on the roads in New England I pretty much have to dismantle and clean my ride weekly. With this rain the salt should be gone now...thankyou mother nature.

Uh, maybe I missed you negating this possibility, but do you think that maybe it's a combination of lack of grease and a chaining that's not pefectly straight? That would explain why it would only creak, or would creak a lot more, when you're mashing (e.g., standing and pedaling).

After you have cleaned, serviced and adjusted all the components on your bike have a good look at all the mitre joints under a strong light for creasing in the paint.

The last creak I had turned out to be a crack developing between the head and down tube.

Lotsa great answers here. Went to american cyclery and they suspected many of the same things, they whisked the bike onto the stand and proceeded to tighten the chain ring bolts, they were tight except for one, the one that needed tightening actually gave the same kind of creak as it was torqued down. I thought that would be it.

It's still there

All along my left foot has been telling me left crank arm. It happens only once in a given direction, if it were the bottom bracket it would happen every rotation.

We can forget everything else drive train related because I'm can still get it with the chain removed. When I find my crank puller I'm gonna pull the arm off and reseat it.

I vote for regreasing and tightening your pedals. I often get a rather nasty creak when I'm standing hard on my left crank (although, the side doesn't really matter I don't think).

i had the simular problem with my left crank arm last fall. as soon as i would put forward or backward pressure on the left pedal it would make a tinking sound. i thought it was the pedal (actually bought new pair) but the sound was still there. i didn't know what else to do so i pulled off the crank, cleaned it (didn't grease it), then put it back on and tightened the crank bolts to the point where my hands where beat red and hurt like hell from the wrench. the tinking magicaly went away.

good luck!

similar thing happened here. them cropcircles just appeared o'ernight

I mean, I tightened up the crank and it went away. I still hear it from time to time tho, in just about the same position as danger man said. Thot it was the crank bolt stripping out...still don't know what causes this sound.

[edit: taking bike apart again this evening, updates soon]

i second bostonfixed's suggestion about the bottom bracket. the fact that the creak responds to pressure suggests shear stress between the bottom bracket shell and the cups. i had a creak like that was infuriating me, not chainring bolts, not crank bolts, not pedals. i finally disassembled the bottom bracket and it had gotten a little dry and crusty between the cups, which are alloy, and the shell, which is steel. a little wire brushing and light greasing and i can sneak up on anybody now.

Hmm... I noticed a similar creaking noise recently that seems to come from my left pedal, possibly only when I use one side of the pedal (stock Wellgo double-sided clipless). Seems like it mainly happens when applying reverse pressure. I'll have to run through these checklists tonight.

My friend had this problem and it turned out to be his BB. The cheap plastic threaded piece had cracked and was falling apart. If not that check and see if your BB threads are properly greased.

Creaking can also have something to do with the taper of a square taper crank. Depending how long/hard you have ridden your cranks and the quality of said cranks it could just be that the taper on the left arm has slighty rounded, I have done it to two left arms, one was a sugino super mighty and the other a crappy sugino. Fixed/no brakes are especially prone to this problem- thanks

I have a creaking sound now, so I just did what anyone would do: ordered sugino 75's to replace the crappy bmx cranks i'm using.

that should take care of it.

I've only had my Sugino 75s since maybe August or September of last year, so I kind of doubt the taper has rounded very much since then. But if they did somehow, I'ma be good and angry.