My BB is creaking on each turn.

It's one of these:

http://www.amazon.com/Shimano-Deore-FC-M521-Octalink-Crankset/dp/B002VS2GBK

Is it okay to ride still until I can get it tightened? There's no play in the cranks.

Cheers.

yea my hope BB is creaking especially when pressure is applied in a high gear, there fine to ride, been riding like that for a while, still need a new one though as its annoying lol

I think it just needs tightening, it happened before and that fixed it. Do you know what tools I need to tightend it?

3 Tools.
An allen key to remove the bolt under the top cap. (10mm I think?!?)
A crank extractor. http://www.parktool.com/products/detail.asp?cat=26&item=CCP-44
and a BB tool http://www.parktool.com/products/detail.asp?cat=25&item=BBT-22

or a friendly LBS who would have the crank off tightened and back together in less time than you picking up a couple of inner tubes and flicked through single track mag 😀

i use a big fat allen key mines x type and to take the cups off just use a big BB spanner

Depends on why it's creaking as to whether it's safe to ride, if the arm is loosethen you may damage the splines, if the cups are loose then you could destroy your BB shell threads.

Thank you all. Will take it to the LBS next week.

Another stupid question – am I missing a crank nut here, or is it just a plastic cover that would go there?

http://picasaweb.google.co.uk/lh/photo/oI434cUREvNLComjZ6bC7w?feat=directlink

You are missing a crank nut.

Is it vital to holding the cranks on? I must have done a few rides with it off 🙂

I've found the exploded diagram for it:

http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/FC/EV-FC-M521-2740A_v1_m56577569830637966.pdf

The bit that's missing – it looks like a cover to me?

Sorry to be thick, I'm no mechanic.

If you have a 10 mm allen key try putting it in the hole you show on the picture. I do not think you are missing the bolt as it is a hollowtech crank in the picture it looks like you can see the faces of the allen key bolt inside the crank arm

Agreed with Coatsy though, will be much more expensive if you damage the splines. LBS it. A decent one won't charge for advice or charge more than a tenner to tighten it.

It is a hollowtech crank but not an HTII. It uses an octalink bb I have a few of them, on the higher models a self extracting crank bolt is used. The inner screws into the bb, the outer using a pin spanner screws into the cranks – you can just about make out the threads in the photo (otherwise used for crank puller). When you unscrew it the inner pushes against the outer thus providing the force to pull the crank off without a crank puller, but an old fashioned square taper bolt should work too. You need to sort it otherwise you will kill your crank – you may already have done enough damage to ensure it creaks in perpetuity. I had an FSA one this happened to.

I can get a 10mm allen key to fit in there.

If I turn it clockwise as hard as I can, will that sort it out until I can get to an LBS? If I understand mefty, the outer is the part that I am missing and doesn't hold it together, it is used only as a kind of counter-force to extract it.

I'm planning to ride Brechfa tomorrow.

(it actually seems to have stopped creaking a bit now, I noticed it at the start of its last ride and the ride seems to have sorted it out somewhat)

I am really confused as I can now see why your allen key is connecting, but can't see where the bolt is putting pressure on the crank, mine which I have just taken off is 8 mm and has a flange which holds the crank to the BB, I can't see anything equivalent in your phto. The bolt may have sheared but then I would not expect to see anywhere to engage the allen key, odd. If the bolt has sheared then the crank will eventually come off, don't know when, I had to hit my FSA one off very hard a few times when the crank extractor destroyed the threads.

It's the stock chainset off a 2009 cannondale prophet, so searches I've done identify it as Shimano M521.

So if I assume that the exploding diagram is correct (see further up), is it possible I haven't actually lost a piece?

On the right hand crank arm, pieces 1 and 2 show an exposed thread?

Or is it piece 1 in, with piece 2 missing?

Just wondering whether to cancel my ride tomorrow now!

Thanks

I found this picture that shows the bit I'm missing.

http://www.chainreactioncycles.com/Models.aspx?ModelID=30968

I've found this picture of the part itself:

http://www.nodari.com.ar/productos/?function=detail&id=2206

you will be fine just couldn't make out the bolt head in the photo, the other bit only functions to get the crank off or as a cover

actually relooking at the photo – are you sure it has not sheared – i would take it out and check to photo you found.

I'll get it out now.

It came out easily, here's a couple of pics:

http://picasaweb.google.co.uk/lh/photo/qg7sXTkC1uCzxAQ8XH4eeQ?feat=directlink
http://picasaweb.google.co.uk/lh/photo/TIJ4pZPPKAkfX3V8o_hDsg?feat=directlink

Looking in my spare parts box, I have this from a Race Face Evolve XC, can I put that in instead do you think? (It seems to fit, although needs an 8mm allen key to put in)

http://picasaweb.google.co.uk/lh/photo/1GYK-BMgTz7cv_Fqp-iudA?feat=directlink

(Thanks for helping on this, I appreciate you must have better things to do!)

Cheers.

The original will be fine – just make sure you tighten it up.

Thanks mate. Will tighten it up then take it to an LBS next week.

To be honest you can ride it without the other bit for ages, i wouldn't spend much sorting it just means you need a crank puller to get the cranks off.

stick the original back on, make sure it is tight. Take the 10mm allen key with you just in case as it is easy to carry. Take it to a LBS next week and ask them to solve the creak. but most importantly enjoy the ride. 😆