Bottom Bracket Size

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ferdy

ferdy

Joined
Dec 27, 2008
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I need to replace the bottom bracket cups on my 1930's Colson Flyer. I grabbed several from my pile of saved cups and was surprised to discover that none of them fit. The diameter in the frame is the same as the more recent one piece cranks but the bearings are about an 8th of an inch smaller. It appears they are shaped slightly different. I'm afraid to try try to force them into the frame. Any one else run into this? Any idea of a source for replacements?

Fred
 
My bearings are okay, it's the size-shape of the cups that's the problem. Even though the diameter in the frame is the standard size the typical cup seems too wide to squeeze in, I's afraid to try to force them in.
 
ferdy said:
My bearings are okay, it's the size-shape of the cups that's the problem. Even though the diameter in the frame is the standard size the typical cup seems too wide to squeeze in, I's afraid to try to force them in.
Click to expand...

I now remember having that problem in the past. My cups were very unevenly worn but I ended out reusing them. I forgot about this. I think for occasional use it might be OK to reuse the cups? I tried putting in modern cups with a vice but they wouldn't go in. Don't try this it is a waste of time. I tried to file replacements down but the metal is too hard. I also tried grinding but it was too uneven and you can't get the inner part without damaging the lips. I tried removing the dimples on one set of replacement cups from a junked cheap big box bike, but for some reason that didn't work either, can't remember why, probably still too big. I have enlarged seat tubes on two bicycles with homemade drum sanders. This takes a few hours. I made the drum sander out of a pipe and used contact cement to hold on 50 grit paper. I used a bolt and nuts to make the end small enough to fit the drill chuck. I used lots of oil to help keep the sandpaper from sticking and tearing. I then used my brake cylinder hone to finish polish it. The best way is to fab a drum that is slightly smaller (including the added sandpaper) than the pipe you are enlarging. It will tear if it is too tight but oil helps keep the paper intact. You just add new paper with spray contact cement when it tears. If you need to enlarge the drum, use tape. I think this would work on your bottom bracket, you just have to go slow, take several days and perhaps do several half hour sessions with lots of trial fitting. This would be a last resort. Perhaps enlarging the bottom bracket and grinding off race dimples might be the best way? Of course you can't take off a lot of metal as the bottom bracket might become too weak. I hope someone else has a better answer as I could also benefit from new cups for two of my 1930s bikes. I hope you don't need to find a woman's donor bike. People that see you riding your vintage bike don't realize the amount of fiddling and fab that it takes to get these bikes back on the road. If you come up with a solution please post it.
 
Thanks guys. Not sure what direction I'm going with this but I will keep you posted. Sounds like no one is aware of any place to purchase a replacement set. Never gave it a thought and have the bike all painted up so I'll need to be careful with the frame. Probably the first one to make this mistake! :headbang:
 
I'd try memory lane or post a "WTB" on here and/or the CABE, to find the original-size cups/bearings.

The questions i have are:
-I understand that the cup are different, but is the frame's shell any different? Does the shell taper in for the unique cups, or is it a straight shot? In short, do you see any reason why running the newer/more common size cups would hurt the frame?

-Do you have the original crank? What's THAT thing like? Have you tried mocking it up within a newer/more standard frame/BB set?

Do you have pics of the BB shell and/or the cranks? I'd like to take a look-see, and i bet others might be better able to advise you if they could take a butcher's at it.
 
If you cant replace the assembly with newer standard parts maybe take the ild and new cups to a machine shop and have them turn the new cups O.D. to match the old.
 
Bicycle808 said:
I'd try memory lane or post a "WTB" on here and/or the CABE, to find the original-size cups/bearings.

The questions i have are:
-I understand that the cup are different, but is the frame's shell any different? Does the shell taper in for the unique cups, or is it a straight shot? In short, do you see any reason why running the newer/more common size cups would hurt the frame?

-Do you have the original crank? What's THAT thing like? Have you tried mocking it up within a newer/more standard frame/BB set?

Do you have pics of the BB shell and/or the cranks? I'd like to take a look-see, and i bet others might be better able to advise you if they could take a butcher's at it.
Click to expand...
The originals have a different taper to them. There is enough difference that I don't believe I could press them into the frame without damage. The newer standard BB set stuff works just fine with the crank, just can't squeeze the newer cups into the openings in the frame. The crank is your typical prewar dogleg, 24 tpi crank (newly rechromed)
I'm traveling but will take some pictures when I return. I appreciate the questions, comments, and suggestions.
 
ferdy said:
The originals have a different taper to them. There is enough difference that I don't believe I could press them into the frame without damage. The newer standard BB set stuff works just fine with the crank, just can't squeeze the newer cups into the openings in the frame. The crank is your typical prewar dogleg, 24 tpi crank (newly rechromed)
I'm traveling but will take some pictures when I return. I appreciate the questions, comments, and suggestions.
Click to expand...
Don't try to press them in, I already tried that. They just won't go in, I didn't damage anything. I used a large bench vice, not even close to going in.
 
So I finally got back to this. I've added a couple of pictures that show the differences. The smaller cup and bearing are from the Flyer, the larger ones are the "standard" size, sorry I don't have calipers to offer an exact measurement. Now I know. I did eventually find a cup that fits, the bearings are good, time to reassemble and ride! Thank you to everyone for the suggestions, and concerns. Fred
WIN_20160331_11_14_00_Pro.jpg
WIN_20160331_11_20_09_Pro.jpg
 

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