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Discussion Starter · #1 · (Edited)
I’m seeking advice on how to clean out the dirt inside of a frame, particularly the chain and seat stays, and how to prevent it from entering the frame.

I rebuilt the bottom bracket (adjustable or fixed cup type, and first rebuild after ten years) on my commuter only to hear a grinding and clicking noises within a few weeks. After taking it apart I found the bearings covered with mud. So I rinsed out the frame as best as I could by pouring water down the seat tube and trying to get it also down the seat stays from the openings in the seat tube. It seemed to be flushing clear eventually.

After a few weeks however I got the noises again, and again opened it up to find muddy bearings. Each time the noise came soon after lots of rain.

I’m not sure how the dirt is entering the frame. Around the axle is my guess. The gap by the seat tube collar, the headset, or the holes in the chain stays are other possibilities. The seat post is sealed on top. The bike is ridden in the rain a lot and I don’t have fenders. Perhaps the stays have dirt in them from years of mountain and road biking. There is also a plastic cable guide under the bottom bracket but the attachment screw seems snug.

I could just replace the fixed cup with a sealed cartridge bottom bracket but I’d like to try and get this fixed cup system to work. Perhaps I should install a plastic sleeve around the axle.

Any thoughts on how to clean the frame and prevent more dirt from entering? The bike has holes in the rear of the chain stays (about 2mm diameter) and appear to be connected internally with the seat stays. Would a shop have a small attachment to blow compressed air into the frame?

Thanks for any advice.
 

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Are you sure it's dirt,

and not rust? If it's a steel frame and has spent a lot of time in the rain, you might have rust sloughing off. When it mixes with the ground metal from the deteriorating bearings it might not look rust-colored. You might have made it worse with that interior washing. I can't imagine how that much dirt can get inside a frame. If it is rust, you need to clean a bit more, DRY thoroughly, and coat the inside of the frame with something to slow the process.

If it's an alu frame I'm stumped. However, ten years of wet riding on a conventional bottom bracket is a lot, and personally I'd replace it with a cartridge bb. They're really way better (especially if you ride in the rain), and they're cheap. I got a Shimano UN-52 for my fixed-gear commuter for 25 bucks, and I never have to think about it. It's got about 5000 miles on it, and I suppose after another 5000 I'll just buy a new one.
 

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Discussion Starter · #3 · (Edited)
Thanks for responding. It is an aluminum frame. It does have a steel steerer tube however but I don’t think that’s the source. It's had lots of use as a mountain bike and commuter in everything from mud to dusty conditions. When I took the headset apart I think I remember what looked like a small amount of clay/mud around the threads on the steerer tube. Maybe that was seeping down to the BB but the holes into the BB seem to be centered on the seat tube and chain stays.

I just looked at the fork and realized the steerer tube is completely open on both ends. Perhaps dirt could have traveled the 16 cm through the tube when riding or laying on the side.

A cartridge BB is probably the way to go but I’m stubborn and would like to figure this out and have some success at rebuilding an adjustable BB. The cups are not smooth but don’t feel extremely pitted either. I took them out and felt the bearing surface with my finger and a ball point pen. The axle was replaced with a used axle in better condition and the bearings were new each time. A friend who has done these rebuilds thought it should work okay. There was some bearing binding when I rebuilt it (without cranks attached) and it seemed okay for a couple of weeks.

The last adjustable BB I took apart was so filled with dirt I just put in a cartridge BB. And that was a used road bike I bought.
 

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BB insert

Art853 said:
A cartridge BB is probably the way to go but I’m stubborn and would like to figure this out and have some success at rebuilding an adjustable BB.
Are you using a BB insert of some sort? Back in the Nuovo Record days, Campy introduced a two part plastic sleeve that served to seal between the BB cups, preventing any contamination from entering from the center of the BB (cutout frames were becoming popular about then). Stronglight made one that had an accordian design. You can create a BB insert from a pop can - cut a strip the right width and then roll it up to fit inside the BB.
 

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Discussion Starter · #5 · (Edited)
I don't have a BB insert (or plastic sleeve). I should try it. That would protect the bearings from dirt entering from the seat tube and chain stay but not if it is still coming in through the axle. Does much water and dirt enter frames down the seat tube compared to coming in via the axle on an adjustable BB?
 
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