Bottom Bracket question

JonS123

Trying to identify a creak, and having tried other things have taken off the bottom bracket to take a look, juding by the fact I could remove the non drive side "cup" thing with just my hands and no need for a spanner, I wonder if that could be it

What I am unsure about is how much resitance should the bottom bracket have? eg if i flick it round (when its out of the bike, and just the BB no cranks etc) it will only do one revolution then stop. Should it be like this or have less resistance

Its a shimano UN26 (square tapered), there is no crank wobble or any other indicators that its nackered, just the annoying creaking noise I can not locate - from looking at it the side towards the non drive side has some surface rust on it, so somehow water has made it in

Thanks!

davis

Well, your cup was loose, and maybe that caused the creaking.

As for resistance, you can find they've got quite a large amount; if you put new bearings in and spin with just the cranks then they won't spin for that long.

Presumably you've tried just spinning the cranks in-situ with no chain? If there's no obvious grumbling/graunching, coupled with the lack of left/right wobble, I'd say your BB was ok.

(Waits for nicklouse to tell me I'm all wrong).

The creak is caused by your pedals. It's always your pedals, always. Well, ok, sometimes it's your saddle rails, but it's definitely one of those two. Unless it's your handlebars, which it might be. Of course, sometimes your dropouts/skewers creak a bit too...

nicklouse

davis
why would i do that.

as above lose cup will be the issis and a bb with nothing attached has no mass to allow it to spin for long.

davis

nicklouse wrote:

davis
why would i do that.

'cos you know more about bikes than I do. (I was kind of expecting to make a muppet of myself)

JonS123

Thanks for the replies, everything put back together, will go for a test ride tomorrow and see what happens

godders1

Creaks from quite a few locations can sound like they're coming from the BB area (pretty much anywhere from the seat tube backwards). Fresh grease and re-seating of the seatpost is another thing to try.

JonS123

The creak has gone, and it must have been the BB, since I tried removing the pedals (striped them down at same time) and cranks and greased all threads etc

Now I have noticed a slight "clunk" on the chain every 2 and a bit revolutions of the cranks when in big chainring and small cog, almost as if the rear derailer is trying to move the chain up a cog but not working, even though I've re-checked its alignment - though I should add the casette/chainring/chain must be due a replacement sometime soon as they must have had the best part of 3000 miles on them

nicklouse

a stiff link in the chain.