If you can't find out what spindle length the manufacturer supplies, it's simply guess-and-check. You can decide where you want the chainline and get a BB to make that happen.
By the way, the guess-and-check method requires only
one bottom bracket to figure everything out. I keep a trashed one around for this purpose. This is the procedure:
1. Install the "test" BB (in my case an old junk one.)
2. Install the crank. No need to tighten it all the way, just enough so that it's firmly on the spindle.
3. Measure the chainline.
4. Use math to figure out how much spindle length you need to add/subtract to get the chainline you want. For example, if you want a 42mm chainline but your test BB gives you 45mm, you need a BB that's 6mm shorter than the test BB (since the length comes off each side.)
Originally Posted by
corrado33
The BB is for a Surly cross check, which has a 68mm wide, standard English threaded 1.37˝ x 24t . First off, what's the 1.37 x 24t mean? Is that the thread designation (another way of saying it's an English thread?)
Yes.