marked001

I'm building up a Fetish Cycles Position frame.. .and I just bought a shimano 600 bmx crankset... how oh how do I know what size bb to buy?? thanks

brunning

depends in part on your rear hub, but a shimano un-53 in 68x109 will probably get you close. i'd double check with someone who owns the frame.

Learn_not2burn

I've been using 68X108 (fsa platinum pro bb) on my fetish, anyone feel free to contradict me if I'm wrong though. My chainline isn't perfect though, this is due to the fact that I am not pleased unless it is completely silent, so I adjust it so much that I actually do more harm than good.

marked001

I"m going to be using some deep v's built up by Iro...and they use Iro's hub... not sure what that hub actually is... so once i get the wheels..is there any way for me to 'measure' anything? or should I just risk and go with your recommendations? much appreciated guys.

queerpunk

sheldonbrown.com has a list of hubs, sprockets, and the chainline they'll yield.
if you follow his links to harris cyclery's parts-->cranks, you'll see what BB's will yield what chainline.

IRO 's hubs (made by formula), with a DA cog, wants a 42mm chainline--that means that a straight chain will be 42mm away from the centerline of the bike. so you want to get cranks and a BB with the right length spindle, so that you'll get a 42mm (or close to that) chainline.

once it's all on, you can double-check by measuring from the center of your seat tube to the center of your chainring.

capice?

marked001

i got it.. sooo...where exactly is a bb measured 'to'.. ?