Bottom Bracket Spindle Length Question
 

Firstly, I've been a long time reader of Bike Forums and finally joined, so hi all. Secondly, i'm sure this topic has been posted a 100 times already, so if you know a thread with an answer for my question please redirect me. And now, the question:

I have a custom Marino frame that has 135 rear spacing. I am currently in the process of trying to fit a 2x10 setup onto it, and the last bit of technical "fun" to wade through is figuring out the right bottom bracket width. I will be using an FSA vero compact double crankset with a 68mm shell width on my frame. Now, most online sources show that the vero should have a spindle length of 110mm. So in my mind, to go from a 43.5 chainline to the 47.5 chainline for a 135 spaced rear hub this would mean an overall increase of 8mm, or a 118mm spindle. Am I wrong?

As a note, I contacted FSA to make sure that I had the correct spindle length and they told me it was 103 and the correct one for my application would therefore be a 108mm. That doesn't make sense to me, can anyone confirm/deny this?

Thanks much, will post pics when I'm all done.

First, you need to see if you need a "power drive" or a JIS bottom bracket (splined interface or square taper respectively). JIS bottom brackets are bog cheap. Being that your bike is non-standard, if you need square taper, I would either use the expertise of an old-school mechanic (this BB design is, like, 20 years behind the state of the art) to give you advice, or experiment a little. Start at 110 maybe, but realize you might need to change. Also, you need to determine if the bottom bracket needs to be symmetrical or have an offset. Good luck!

If it's "power drive" you need, then just go with what FSA recommends. Also, you might get better help in the "mechanics" section of the bikeforums, since this tech is so out of date.

When I first installed an FSA Vero Compact double on my Specialized Sirrus years ago, I left the 122.5 BB on it. It worked all right, but would occasionally drop chains to the inside. When that BB showed wear, I replace it with a 107, which worked fine, and shifted fine. I later moved that crank to a bike with a 113 spindle, and it worked fine, and shifted fine.

Personally, I would get a 113, and never think about it again.