'38 Schwinn Motorbike Klunker - Sealed Bottom Bracket Question

Apr 22, 2019
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First post here! Disclaimer - I did try to search first to get an answer to this question.

I recently completed a Klunker build and had a local bike shop help me with the bottom bracket purchase and assembly. My issue is I don't think they did it correctly. The bottom bracket was shimmed and seems a bit too large. The crank is a Truvativ Stylo Single Speed 1x 33T Crankset ISIS Drive 175mm.

My question is this - does anyone know what BB setup is the best to use on this frame? I'm just looking for some guidance here. Thanks for any help in advance!
 
Oct 15, 2008
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Crystal Beach, TX
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Sounds like they used an adaptor to mate the 3 piece crank to your vintage frame. I had to shim mine a bit. I am thinking that beach cruiser/bmx bottom brackets have not changed since 1938. Post a pic and we will have some better answers.
 
Jun 20, 2010
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Agreed with the adaptor comment. Your old Schwinn has an American sized bottom bracket and the ISIS B.B. would be English threaded sealed cartridge style. There are press in adapters that make this combo work.
 
Apr 22, 2019
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Thanks, Big Orange Cat! Where did you source the threaded insert? Do you have a brand or size that I can look for? I've seen them on eBay, just want to make sure I'm looking for the correct one. THANKS AGAIN!
 
Dec 13, 2011
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Thanks, Big Orange Cat! Where did you source the threaded insert? Do you have a brand or size that I can look for? I've seen them on eBay, just want to make sure I'm looking for the correct one. THANKS AGAIN!
I pulled it off another bike I found, but should be a standard American to Euro bottom bracket conversion with an Euro sealed bottom bracket.

Going to need one of these too:
 
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Sometimes you have to grind on the BB shell to get these with the 3 bolts to fit. In the 1980s I used a BMX BB adaptor and that worked without any problems and was easy to install. I don't know if the latest versions are any good but they are about as simple to install as an American BB. You might need a different spindle with a different offset to get the chain line right, but probably not. $20
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