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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 05-27-08, 03:44 PM   #1
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Is this a problem? Crack in my new bottom bracket.

I have a 2004 Giant Boulder SE. The bottom bracket bearings wore out on me, so I got them fixed last month. Since I don't have the tools or a lot of extra money to deal with any "trial and error" stuff on my behalf, I took it to a well known bike shop. They were very nice and seemed to take their job seriously, so I decided to use them to fix my bike.

I've taken the bike on two rides since I got it fixed. One was a 7 mile ride on a decent trail, and the other was about 20 miles on flat macadam.

While putting the bike back in the garage today, I noticed this.

What do you guys think?

http://s2.photobucket.com/albums/y36...060265copy.jpg
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Old 05-27-08, 04:08 PM   #2
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It looks like the plastic bb collar is cracked. Not a big deal but you ought to have them replace it anyway if they guarantee their work.
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Old 05-27-08, 04:21 PM   #3
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Yeah, I figured it was just a collar. Do you really think it's worth lugging back in there to have them replace a plastic piece that isn't really a big deal, though?

My bike has some pretty intense battle scars, so seeing this minor crack makes me think "If it aint broke, don't fix it." And since it rides smooth and pedals great, I'm tempted to ignore it.

Do you guys think I should have them take a look at it, though?
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Old 05-27-08, 04:30 PM   #4
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Ya, I am in agreement with TimJ and Roasted. That is like complaining about getting two pickles on your hamburger instead of three.

When I read your post, I thought you were hosed, but when I saw the pic, it's just like....

Well, anyway. Get a new collar. IF the shop gives if for free, thank them with a big smile. IF they charge you, pay with a five dollar bill and use the change to get yourself a really nice coffee.
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Old 05-27-08, 04:34 PM   #5
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Thanks, guys. I just don't think I know "enough" about bike mechanics just yet to really have leverage of justifying a point. I just wasn't sure if it would lead to further problems, like maybe allowing dirt in which could wear everything out at a much faster rate or anything. The way I see it, is that it's minor. But... I checked here to seek more experienced opinions.
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Old 05-27-08, 05:02 PM   #6
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But it most surely was caused by a mechanic over tightening it (been there, done that), so I would expect them to replace it for free (they have a drawer full of aluminum or steel replacements that will likely fit and won't crack). If you leave it be, you may be dealing with an annoying creak down the road.
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Old 05-27-08, 05:17 PM   #7
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But it most surely was caused by a mechanic over tightening it (been there, done that), so I would expect them to replace it for free (they have a drawer full of aluminum or steel replacements that will likely fit and won't crack). If you leave it be, you may be dealing with an annoying creak down the road.
An annoying creak? The only thing I'm really concerned about is the bottom bracket staying intact and holding up. If a month from now I can expect the bearings to wear out, then yeah I'd like to take care of it. But like I said, if it's really not a big deal, and the actual guts and metal parts of the bracket will hold up regardless of a hairline crack in a plastic collar, then I'm not worried about it getting fixed.
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Old 05-27-08, 05:28 PM   #8
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Well, it's a sealed bearing unit, so nothing will happen to your bearings. A creak every pedal rotation would annoy the hell out of me, though. I suppose it could eventually unthread itself, but probably won't.
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Old 05-27-08, 06:01 PM   #9
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If it unthreads itself, should I just grab a new one and pop it on? I haven't exactly mastered the art of dissecting a bicycle, so I'm not 100% sure about how these parts interact with one another as you guys do.
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Old 05-27-08, 06:17 PM   #10
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If it unthreads itself, should I just grab a new one and pop it on? I haven't exactly mastered the art of dissecting a bicycle, so I'm not 100% sure about how these parts interact with one another as you guys do.
Unfortunately, there is no standard size, so it can be a bear to find a good fit. That's why I'd recommend bringing it back to the shop if it isn't too big an inconvenience for you. Otherwise, if it becomes problematic in the future, you'll have to hunt down a collar that fits (again, been there and done that, and it wasn't easy). You also need some tools and know-how to remove the crankarm and install the collar.
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Old 05-27-08, 06:27 PM   #11
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The crack can't spread and the collar/cup won't unthread by itself so there is no harm in ignoring it. It's not a functional problem.
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Old 05-27-08, 07:36 PM   #12
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Is this collar what actually houses the entire assembly inside the frame? Or is it just kind of... there for the sake of holding back potential dirt?
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Old 05-27-08, 08:30 PM   #13
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Is this collar what actually houses the entire assembly inside the frame? Or is it just kind of... there for the sake of holding back potential dirt?
It holds the cartridge body in place on the non-drive side of the shell. The cartridge is a completely sealed unit.

http://www.parktool.com/repair/readhowto.asp?id=94
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Old 05-27-08, 08:58 PM   #14
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It holds the cartridge body in place on the non-drive side of the shell. The cartridge is a completely sealed unit.

http://www.parktool.com/repair/readhowto.asp?id=94
I see. Well as long as the darn thing will stay in there, I'll be happy.
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Old 05-28-08, 03:23 AM   #15
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Looks to me like you might have a crack where the chain stays attach??
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Old 05-28-08, 09:28 AM   #16
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Looks to me like you might have a crack where the chain stays attach??
Where? The only questionable thing I see regarding the chain is on the far left on the actual chain. If that's what you're speaking about, it's not a crack... it's the very edge of the next link.
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