its just a little project im doing for a short commuter to work. i have almost everything i need besides the head set and bottom bracket but i read you need a special adapter to put the BB in. I was wondering if anyone has done this conversion before or if anyone knows what size headset, BB and adapter i need for this bike? its a 70s Schwinn Chicago continental i attached a photo to this thread. any help would be greatly appreciated!!! im new to bike mechanics but i have worked on cars for over 10 years so im pretty good with a wrench.

It should just be a standard Square taper English bottom bracket I can't imagine them using Ashtabula cranks but it was a lower end bike so it is wholly possible in which case I am unsure of what to do (since I have never actually worked on Ashtabula cranks and don't have much knowledge or care for them)

For square taper cranks you would just need to figure out what spindle length and taper (ISO or JIS) you need and that would be dependent on the cranks you get (and generally manufacturers tell you what they recommend for length and what spindle it would be)

Why not just get an Ashtabula crank that fits as is? There cheap and heavy,and bomb proof like the frame

Truvativ makes an adapter to use english threaded bottom brackets, but might be simpler to stick with a 1 piece crank. You will have trouble trying to make that threadless fork work because you can't just find something new to fit. These kinds of Schwinns had larger diameter head tubes that fit 1" english threaded steertubes. You"ll need a complete headset and threaded fork.
Info:
Parts for older American Bicycles

For the bottom bracket, your options are 1) reinstall a one piece crankset or 2) order a truvativ bottom bracket adapter and install it will a cartridge bottom bracket and 3 piece crankset.

As for the headset, genuinebicycleproducts.com sells a headset that lets you install a 1 1/8 threadless fork. This sells for about 50 bucks. Its essentially a 10 dollar headset that's been turned in a lathe to fit your headtube, but if you don't have a buddy thats a machinist its your only option short of installing the original headset and fork.

I will note that the site mentioned above also has aluminum seatposts that will fit varsity/continental.

Anyway, good luck with the build!

This adapter is a charm to install and work with. A blissful dream compared to some more modern press-fit OS/BB30 adapters.

to OP.. I just recently converted a 79 Schwinn Le Tour IV. Mine didn't have an American type BB.. but I believe you had to use one of these to do the conversion
SBS Bottom Bracket Conversion from American to Euro Adapter | eBay

to hobbitman.. for me was easier to use a 1 1/8 quill adapter then put on the stem I wanted.
https://www.amazon.com/gp/product/B00...=sr_1_2&sr=8-2

since I can't post pics yet.. link to my bike.
https://goo.gl/photos/RJA1fv7kUv1U9chd9

There's usually about 10 different solutions to the same "problem" with a bike. The SBS appears to be the same thing as the Truvativ adapter, just more expensive.
https://www.amazon.com/Truvativ-00-64...o-euro+adapter

The quill to threadless adapters are a bit kludgy imho. You get the positives of a a removable face but still without the convenience of a true threadless setup. Personally, I'd just get a cheap threadless fork and buy the headset I posted. It costs a bit more, but you'll only do it once in the foreseeable future but the result is cleaner, lighter, and more convenient to adjust. That's just my personal opinion though.

Nice bike though! A good mix of retro and modern.

@hobbitman yah many ways to skin a cat.. but I do hear you on the conversion of threadless. Thinking I might do the same for my bike, I like the chrome fork look, why I went my route with quill adapter. hrmm see if I can find a threadless chrome fork.
@mjhoffman887I did find this that will work as well and not cost so much. Only issue is only comes in 2 sizes. Any updates on your bike.
https://www.amazon.com/Sunlite-Conver...bottom+bracket

i installed the truvativ adapter and dropped the bike at the shop so they could do all the measurements for the BB. i have a origin 8 crank set they put everything together for me 80 bucks including brand new BB and chain i only need 1 adapter so i can put a thread-less handle bar set on and im done until i decide when im going to paint it thanks guys heres a pictures