American BB for BMX

[badmother]

Hello. Could somebody plse tell me the dimension of the bottom bracket housing of the American cottered threadless system? (Threads on the axel). Need this to try to buy an adaptor to fit a modern BB. Hope somebody can help!:)

[chicagotypewrit]

i want to help but i have never heard of a cottered threadless system maybe im just stupid. but are you talking about the bearings where the spindle for your cranks go?

[badmother]

Yes. Cups is just pressed in, no threads. Think it is called Thompson. Need to know the diameter. Mine is approx 40 mm (cannot measure accurate unless I remove the shells for the bearrings). Approx 70 wide. Is this standard?

Need to know becouse I want to know if I can buy this one http://www.sjscycles.co.uk/product-SJSC-Gusset-A-Cup-Converter-American-68mm-(BMX-1-piece)-to-accept-English-(threaded)-68mm-systems-15019.htm for a easy upgrade. Tis one just say: "Gusset A-Cup Converter American 68mm (BMX 1 piece) to accept English (threaded) 68mm systems." Need to find a solution, but nobody tell you the radius (like mine is 40), just how wide it is (68, 70, 72 and so on). Can anybody help?:D

[castanagajt]

darn I hate to say but here in the states the american to euro cup conversion since 1998 when Bullseye closed their doors. Profile made the Profile Evolution came around 2000 yet short lived which the american sized cups get screwed on and install the profile cranks.

The trend never caught on here so we won't have a conversion for you on that. Perhaps you should write this on the mountain bike forums in this site and they may have a better answer than us bmx guys. I believe that they do this type of converstion much more than we did. Well Euro conversion. I hope this helps somewhat.

[ascend]

Tis one just say: "Gusset A-Cup Converter American 68mm (BMX 1 piece) to accept English (threaded) 68mm systems."

The "American" and "English" bits tell you the radius (it assumes you already know that these are key words). "American" is also known as "one piece", "one piece crank", and "Ashtabula". For a nice table comparing the names and their sizes, see:
http://en.wikipedia.org/wiki/Bottom_bracket#Shell_diameters_and_threading

[badmother]

Thank you for trying. Found alot of info, but no solution yet. I tryed to post in the Vintage forum, maybe somebody there has done this already.

[CMcMahon]

There was/is no true standard for American BBs; the BB shells were all slightly different in width and inner diameter. I'm confused as to exactly what you're trying to do, though; are you trying to put new cranks in an old frame, or old cranks in a new frame?