So tell me about bottom brackets...

[KnottedYet]

I was looking at bottom brackets for my bike just so I could switch to a new Campy crank. My mechanic said they usually last about 4,000 miles. He showed me a used Campy bb (for $20) that he said had a good 2,000 miles left on it.

400 miles sounds kinda weird for a bb to fail.

[mimitabby]

What kind of bike is it? What kind of bottom bracket is it?

[DebW]

Is this a sealed cartridge bottom bracket? If it were a serviceable cup-and-spindle bottom bracket, you could take it apart yourself, repack it, and adjust the bearings properly. You can't do much with a cartridge. How do the cranks attach to this bb? Play could either be in the bb itself, the bb attachment to the frame, or in the crank-spindle attachment. I would assume neither of the latter is true if the mechanic checked it. Personally, I wouldn't keep riding a bike with play in the bb. The front derailleur won't shift properly and it will wear your chain quickly and feel bad. What brand of crankset do you have, and is the bb a traditional square-tapered spindle, ISIS, or something else?

[VeloVT]

I will have to check the specs on the bottom bracket -- i don't know exactly what it is. I know it is an ISIS bracket -- the crankset is FSA (carbon). The other components on my bike are Ultegra... the drivetrain is all still what came stock on the bike, which is a Felt F50. (My first road bike, knew NOTHING when I got it and would have chosen differently if I had known more, but i got a fantastic deal on it).

The movement in the bb is small right now -- I can't reliably reproduce it with my hands when the bike is in the stand (the mechanic, a bit burlier than me, could, however). however I find it quite noticeable when I ride.

EDIT: Deb, according to the Felt website the bb on my bike is an FSA ISIS cartridge bb.

thanks!

[roadfix]

FSA had interface issues in the past between crank arm and bottom bracket....mainly developing some play. Ask your mechanic about this.

[Kitsune06]

Re: bottom brackets:

Mine is squeaking something horriffic, which is driving me nuts because it's *new*.

I expect it's a cartridge. any ideas? I've ridden it in rain but that shouldn't really affect it... =P

[DebW]

Re: bottom brackets:

Mine is squeaking something horriffic, which is driving me nuts because it's *new*.

I expect it's a cartridge. any ideas? I've ridden it in rain but that shouldn't really affect it... =P

If it's new and your LBS installed it, take it back to them and get it checked for free. It shouldn't squeak. Does it squeak when you turn the crank by hand? I'd pull off the crank arms and check the bb independent of the crank. When you put the arms back on, make sure they are installed VERY firmly. Is there movement between the bb and the frame shell (this is easier to test with crank arms on)? You could drip some oil into the spindle/bb interface if that is the origin of the squeak, but a squeak there is probably indicative of faulty tolerances in manufacturing.