Bottom Bracket Question
 

I'm new to square taper cranksets - started out on the current external bearing stuff.

I've got two bikes that I want to replace the cranksets on: a '97 Bianchi Trofeo and an '87 Centurion Ironman. The Bianchi has a 52/39 Miche crankset on it, which works okay but seems to be constructed of case-hardened margarine and looks kinda cheesy to boot. The Ironman has a Biopace crankset in good shape, but it's a 52/42.

I'm thinking about replacing the Ironman's crankset with the Velo Orange compact, and the Trofeo's with either the Velo Orange compact or a used Campy standard. Assuming the BBs are in good shape, do I need to change them to go with the crankset, or is it just an unbolt-the-old-and-attach-the-new operation? If I do need another width, how do I determine what width?

Thanks!

Maybe. The biopace has JIS tapers which should work with the VO crankset. I THINK the Miche and the Campy used the same tapers, but they may be slightly different (ISO). You may have the same problem with the VO crank on the Miche BB axle where they appear to fit, but either bottom out before the crank bolts are tight, or do not go onto the axle far enough.

In either case, older crank axle tended to be longer, engaging the crank spider more-or-less under the big ring. Newer cranks had shorter axles. It is possible that yor chainline will not work when mixing and matching cranksets to BB axles. BB axles came in a variety of lengths and used to be readily available. Not so much anymore. The bottom line is you will simply have to try it and see if it works or not, swapping BB axles to match, or simply going with a new cartridge BB.

I took a standard Trofeo like yours, that had a Miche crankset.
I simply took the Miche off and bolted on a Veloce.
http://i261.photobucket.com/albums/i...s/P1120738.jpg

As Balindamood says it is all about the taper and length. Also I suspect it won't be an issue on the Miche BB but the 105 may be offset toward the chainring/drive side.

I never realy understood the whole compact drive. We are still running something like a 11-23 or 12-25 9/10/11 spd in the rear so what is the advantage of a 3448 chainwheel over a 42/52(3) other than lower top end?

BTW depending how small of an inner ring you want you could make that 105 crank a compact, you could do a 38/48

With the setup I have on my two "modern" bikes, I spin out in the 50/12 combination at ~35 mph. That only happens on downhills, and they're few and far between where I live. ;) I normally run in either the 50/21 or 50/19 (12-27 cassettes). I do okay with the 52/39 on my Bianchi, but would probably be happier with a 38 small ring. I'm going to play with the 42 for a while to see how it works out. From what I understand the smallest Biopace ring is 40t (130 BCD), and they're hard to find.

You don't need to use Biopace rings you can use any round 130bcd rings. I would use either both biopace or both round.

I know, I just want to try out the Biopace rings to see what they're like.

Your Veloce crankset is en route, as of Monday.

Thanks, Rob!