So tell me about bottom brackets...

[VeloVT]

This forum is so great...

So back in the fall/early winter (last time I put significant miles on my road bike) I was beginning to notice that there was some play in the cranks. Mostly I'd notice when clipping in (especially when I was getting off to a "running start") or when sprinting -- and it was subtle, at first I wondered if it was actually an issue with the pedal bearings -- basically, when apply significant torque, there would be a little um, catch or slide -- probably just millimeters, but there...

So I took my bike in for miscellaneous things last week and asked them to look at this problem. This afternoon I went down to the bike shop and talked with the mechanic who checked out my bike -- and he told me that my bottom bracket is going. To put this in context -- I have 400 miles on the bike. Ridden in the rain once or twice, but it lives in my apartment and I've never **left it** outside when I have ridden in the rain. I wouldn't say I've ridden it in especially sandy or grimy conditions either. I asked him what the average lifespan of a bb was, and he wouldn't commit ("there are so many factors, what kind of riding you do, what kind of conditions you ride in").

On the one hand, it's not a huge expenditure, but on the other hand, it seems like I should get more than 400 miles out of such a basic, integral part of the bike. Can anyone with more experience give me an idea of what I should expect out of a bottom bracket, and also what I might have done to wear one out so quickly? (I'm not super small, but not big either -- 5'6" and 120).

BTW, the mechanic said, "the movement is so slight, I'm really surprised you could notice it at all. If it were my bike or my wife's bike, I'd ride it for a while longer -- you've probably got another couple of hundred miles in it. I've ridden bikes much farther gone than this." Any opinions on this -- on the one hand, it's tempting, but on the other hand, I feel like shortly it will come to really bother me -- there just shouldn't be play in the cranks, you know, it feels really wrong, even though it is subtle right now. I like to push myself sometimes when I ride, and if my bike is off, I worry I"ll find it frustrating... Also, he said that as it got worse, the shifting would start to feel funny -- making me wonder, if I do let it go a little while, do I risk untimely wear on other components?

And one last thing... mechanic told me that the bottom bracket that came stock on my bike (Felt F50) was low end and I could probably get more life out of a better one. This sounds fair -- any tips on what I should avoid and what I should look for when I do replace it (whether now or later)?

Any advice from the more mechanically experienced is appreciated!

[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.