Need help choosing the right bottom bracket.
 

need help finding the right bottom bracket for this frame. This bike originally came with a cotter pin bottom bracket and im trying to upgrade to a square taper bottom bracket but i dont know which one to get. I believe its a schwin varsity but im not sure. please help!

heres the bike:
http://bikeforums.net/attachment.php...hmentid=318500
http://bikeforums.net/attachment.php...hmentid=318501
http://bikeforums.net/attachment.php...hmentid=318502

heres the crank ill be using. just a simple single speed crank from ebay
http://bikeforums.net/attachment.php...hmentid=318503

Its not a Varsity, its an early Nishiki, pre 1975. Varsity did not come with a cottered crank. Its good news that it is not a Varsity. Varsity would be more work to convert.

Spindle length is determined by the crank you bought, not the bike it is going on. Suggest you contact the seller. Or play around with various spindle lengths (do you have a co-op nearby?)

Best to buy a crankset with a bottom bracket, its less hassle.

Simple UN26 cartridge bb is a good choice, and only $10 on line.

Hi. Measure the width of the shell where the BB threads in. If it's 68mm, you most likely have an English threaded BB. This is the most common type. If it is a Nishiki this is your threading.

Next you need to determine length. If you want to use that crankset, the manufacturer or velobase might be able to give you the correct length. But realistically, almost any "single speed" BB will probably work. If you get one of these in the 68x110 size it is probably going to be fine. If you have a way to test fit a few sizes, you should do that. A LBS will probably also have what you need and can find the correct size for you. If you want to upgrade slightly you could get one of these. If you don't already have it, you will need this tool to install the BB.

Hope that helps.

yes i do. whats the most common bb size? 68X113?

You may want to read this:
http://sheldonbrown.com/chainline.html

I measured my BB shell and it is 70 mm. english threaded. I searched and all 70 mm bb's are italian threaded. can i possibly run a 68 or 73 mm bb ?

If you use a cup & cone type BB (as opposed to a cartridge), you can mix 'n' match spindles and cups: use English thread cups with a 70mm spindle. :thumb: