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Unlike the rest of the broken bottom bracket questions, my bottom bracket does not make any noise or feel like anything is grinding.

There is about 1/2cm of play left to right that i can see on the top chainring. I can definitely feel it being loose.

What is the worst amount of damage that I can do to my bike riding like this? (assuming that I dont fall off and die etc because of this little matter)

The bracket itself is new(ish) it was installed there about a year ago, but I did ride 50 miles per week on it since.

What could have caused this to happen? My best guess right now is that someone did this to my bike because I park it out doors while I am at work.

edit: My level of expertise in that area of the bike is pretty low, so here is a video of what is happening:

(set quality to HD)

I noticed that on the side of my chainrings there is a noticeable gap between the seal and the bottom bracket.

So what is going on here? and more importantly can I fix it myself without special tools

Can I expect any kind of a warranty from the bike shop who put this in a year ago ?

Solved: Took out the bottom bracket. It is fine and so are the cranks. The threads on the frame are not fine though. I need a new frame :P

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  • Could you provide some additional detail? What kind of bottom bracket is this? Where is the play that you are seeing? Is the spindle moving side to side or the cups?
    – psycling
    Commented Feb 4, 2014 at 19:27
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    Are you sure it's the BB, not the pedal arm itself?
    – Alexander
    Commented Feb 4, 2014 at 20:05
  • 2600 miles is exceptionally low for a bottom bracket to die even if they're neglected in the rain and snow, and they're not exactly easy to damage directly.
    – Batman
    Commented Feb 4, 2014 at 21:10
  • Sounds more like the crank isn't secured to the BB axle. Draw us a picture, your terminology is inconsistent.
    – Emyr
    Commented Feb 5, 2014 at 11:10
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    It came out easily.. along with the threads of the frame. :P
    – mkoryak
    Commented Feb 7, 2014 at 18:32

2 Answers 2

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Here's a quick test. Grab the crank arm that you say is moving and wiggle it. Does the arm on the other side move? If so, you've probably got a bottom bracket problem. The answer then depends on whether you have a sealed or loose bearing botton bracket. As mentioned previously, a sealed shouldn't do this after 2600 miles. (Neither should a loose bearing, but it is more likely).

If the other arm is not moving, then the one wiggling is probably coming off of the bottom bracket spindle (the axle). The spindle may be rounded off, or the crank arm may be rounded off. The only way to really tell is to take it off and see. This probably means that it wasn't installed securely in the first place.

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  • If the crank arm is not loose, check whether the chain ring itself is secured correctly.
    – arne
    Commented Feb 6, 2014 at 9:04
  • updated my question with the video of the problem.
    – mkoryak
    Commented Feb 6, 2014 at 19:41
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    looks like a bottom bracket problem. And by the looks of it, you have a loose bearing bottom bracket. You will need a few specialty tools: crank puller, bottom bracket wrenches, etc... try to find a local bike co-op near you and they can help for cheap. EDIT: just saw your solution. If the threads are gone on the frame, you might be able to chase them... depends on how bad they are. Again, looks like you're in a city. Find a local bike co-op and they may be able to help
    – Booker
    Commented Feb 11, 2014 at 18:13
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The worst amount of damage is, that you will can not get the BB out of the frame, therefor you'll have to change the whole frame (thou I never saw a BB that can't be pulled out).
Yet your bearings are surely already totally destroyed, and maybe the axle too. As soon as you will replace them, it's better and it will be easier to do.

About the matter of it. You should check for loose in your BB from time to time. Maybe it wasn't screwed well or something, and with the time and lots of riding it's unscrewing. When it's a little unscrewed it begins to damage itself from inside and the more you ride on it, the more damage it will do in future rides starting by destroying the bearings, then beat out gaps in bearing cups (that's why they so hard to unscrew) and gaps on the axle.

Worst with loosen cranks. The cranks must be tighten very well. If a crank isn't tight enough, it will unscrew, and the damage there much worst. The pedal will fall, and the rider can really fall down in mid of street and can be damaged by traffic up to death.

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