Bicycle Mechanics - Bottom bracket

How do you know if the bb is going bad?
Do you think that a bb could make a noise only in a certain postion like at 12 o clock postion? only?
Why? Because my noise problem thats been going on for some quite time seems to me that it is the bb!
I hear a crack, pop, sound when the right side crank comes over the top (12 clock ) WHEN I PEDAL AT A FASTER SPEEDS LIKE ABOVE 16mph! Not at slower speeds! I tryed everything to eliminate and im leaning to the bb! Whats your imput?

Open it up! See what's going on in there! It sounds like it's just worn out. Put in new bearings or a new sealed unit.

... it *could* be that this is a chainring or cog thing, and below 16 mph, you're not in the offending gear.

Not a cog thing. I changed wheels with different cassette. I cant tell if chain ring is bent! Did look at it closlely, any sugestions?

More likely your pedal or cleat. The cleat could be slightly loose in the pedal, and shifts position slightly as your foot comes over the top. Try pedalling with just one foot and then the other. Also could indicate a slightly loose crank.

How do you know if the bb is going bad?
Do you think that a bb could make a noise only in a certain postion like at 12 o clock postion? only?
Why? Because my noise problem thats been going on for some quite time seems to me that it is the bb!
I hear a crack, pop, sound when the right side crank comes over the top (12 clock ) WHEN I PEDAL AT A FASTER SPEEDS LIKE ABOVE 16mph! Not at slower speeds! I tryed everything to eliminate and im leaning to the bb! Whats your imput?

It's much easier to find what's happening to the BB spindle if the cranks are removed; removing the weight of the cranks/pedals makes it very easy to feel even the slightest roughness in the BB bearings.

- Wil

Try to move the cranks from side to side to determine if the BB is worn. If you have an adjustable BB (http://parktool.com/repair/readhowto.asp?id=93), you can rebuild it by cleaning and regreasing. If it's a cartridge bottom bracket (http://parktool.com/repair/readhowto.asp?id=94) and has lots of play, you may need to replace it. Assuming there is no play in the bottom bracket, you can probably get rid of the creaking by removing the BB cups and cleaning/regreasing the threads of the shell and cups.

it could be you pedal.

Could be your seat. The Brooks on my fixed gear starts singing at a certain cadence/speed.

Like all these things, it is a process of elimination, and it could be places other than the BB. Pedal, even rear hub bearings are some options, too. But try hockey's suggestions on checking BB wear first.