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Old 06-06-11, 12:46 PM   #1
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How did this happen? - Bottom Bracket Bearings

Since I got my Author Matrix bike out of storage (7 months) its had some play in the bottom bracket which has gradually been getting worse. I took it apart today to find that one of the bearing cages had completely rotten and all the bearings fell out of that cage causing about 10mm of play. How could this have happened, the bike was always stored in a dry garage?

For the time being I put some thick grease into one of the bearing 'cups' and laid the bearings into that, then put what was left of the rotten bearing cage back on and re-assembled everything. What am I looking at replacing, just the bearings or getting a sealed bottom bracket unit?

Last edited by kamilb1998; 06-06-11 at 12:52 PM.
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Old 06-06-11, 01:12 PM   #2
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Humidity in the air got in... somewhere. Not nec. in the bottom bracket, but any water that got in, it's going to try to find the lowest place.
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Old 06-06-11, 01:44 PM   #3
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Probably not serviced in Decades, I'd say, Buy a new sealed bearing
cartridge Bottom-bracket.

Bring the old axle in to the bike shop to get a length match.

you may have more catch-up from the interval since last bike maintainence work.
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Old 06-06-11, 03:49 PM   #4
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With temperature changes, water can condense inside the frame tubes and dribble down to the BB. Really, seriously bad there, guy. Spring for a sealed item.

I had one old BB I opened up and a petrified wasp fell out! No idea how the little guy got in there, maybe the owner was in the habit of removing his seat to prevent theft.
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Old 06-06-11, 03:59 PM   #5
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If the bearing races are OK(chances don't look too good) you can put new bearings in with no cage.Otherwise,buy a new sealed unit and be done with it.
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Old 06-07-11, 04:21 AM   #6
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Every time I get caught in a heavy down pour, for an extended time, I remove the BB. Most of the times I'll find water droplets in the BB cavity. I wipe clean the cavity threads, and use anti-seize on the BB threads; this makes disassembly easier. Even though it doesn't rain that much where I ride, it is still extra work, but it does pay-off in the long run.

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Old 06-07-11, 09:40 AM   #7
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You would use 11 1/4" balls on each side without the cages. That's the worst case of bottom bracket neglect I've ever seen and I only work on bikes that are at least 30 years old.
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Old 06-07-11, 12:37 PM   #8
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Sorry to say that your BB is toast. With that much corrosion having occured the bearing tracks are now badly pitted and that's going to cause the BB to run rough and wear out the balls and the bearing tracks in the cups and axle in short order so that it'l just get worse and worse. If you need to get the bike together just to ride for a few days to a week until you can get a new cartridge BB then ditch what is left of the cage and put in an extra ball to "fill" the races. Just be aware that you've only bought a little time. That BB is a rolling disaster which is living on borrowed time at this point.

Your best bet is a replacement sealed cartridge BB. That much rust also suggests that you've got the condensation issue mentioned already. This easily happens in garages that have no heat source and go through big temperature shifts. To more readily allow air to flow and keep the frame dry internally a "drain hole" at the lowest portion of the BB shell is a nice idea. Also be sure to butter up the threads and the entire inside of the BB shell with a light coating of grease.
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