so im doing my first fixed gear project with a 75 schwinn contenintal and i know i need different wheels and cranks, my problem isnt in the wheels but what size bb i need, everything is in a different dimension than what Im used to with bmx. I have what i call an american or standard bb bracket but everything i look at is in either mm or cm. Ive tried to get a conversion through google and other searches but nothing is ever consistant with what I learn. ive also been considering the ebay conversion kit with eighthinch conversion. keeping in mind that im just starting is this a decent deal if it will fit my bb? Im on a budget and know from bmx how building up a bike goes so im not expecting perfection, just not trying to waste money.

Thanks for any input!!!

Standard BB should be 68mm wide.

but what is the bearing/cup diameter? I noticed that conversion kit I like is threaded so I belive it may be what i call a euro bb... but even if it is, is there a american to conversion kit? i know they make american to mid or spanish bb for bmx but like I said im pretty limited to bmx as far as my more than basic bike knowledge goes. Im pretty mechanically savy given I work on cars too but I lack the dimension/size knowledge i need to finish what I got started.

Your frame has an American BB shell. To use a modern ("euro") BB, you need one of these:

https://www.amazon.com/Truvativ-00-64.../dp/B000VT550K

^^^ That's definitely what you're looking for. I have used one of these adapters that Scrod linked. It works pretty well. I think the hardware uses a 4mm bolt, which is kinda lame. I knocked my adapters in with a mallet before tightening the hardware. I wouldn't be surprised if they stripped very easily trying to drive the adapters into the shell.

thanks for the link! pretty well sure thatll make it fit. they call it an english bb so Im assuming euro is the same thing.

No prob. English-threaded is the same as what used to be commonly known as a "Euro" BB.

You'll definitely need to press the adapter into the shell before tightening the bolts.

You can use a BMX 3 piece crank and b.b. I have done that on a couple of old Schwinns with American sized b.b.s I've even used an old one piece crank before.