[LostBoyScout]

Hey, quick question for you 's...

Is the eccentric BB the same size as a BMX BB, or different?

I am thinking about a custom frame for next year, which I want to be designed to run either geared or SS, and have vert dropouts. I am thinking eccentric BB, and a replaceable derailleur hanger x2, with one shaved down to work perfect for SS.

 

[recidivist]

Your typical tandem/SS eccentric bottom bracket assembly consists of a an oversized BB shell and an eccentric. A (normal 1.375" x 24tpi threaded) BB then threads into the eccentric. I don't see any reason they couldn't make an eccentric which fit a BMX bottom bracket, but I wouldn't swear such things exist off-the shelf.

(A quick check of ceeway's web site shows eccentrics available with 54 and 57 mm ODs, while the BMX BB shell is 51.5mm ID)

Alternately, I think the oversized tandem BB shells are larger than BMX BB shells. One could make an adaptor (a lot like a BMX-to-MTB BB adaptor) to fit a BMX BB into a tandem BB shell.

 

[LostBoyScout]

Thanks for the info, and your Spot is SIIICCK!!