re: [CR]bottom-bracket woes


Date: Tue, 16 Sep 2003 22:09:45 -0400
From: HM & SS Sachs <sachs@erols.com>
To: chasds@mindspring.com, classicrendezvous@bikelist.org
Subject: re: [CR]bottom-bracket woes


Charles Andrews asks:

After trying, manfully ;>, to handle this problem myself, I've realized I'm stumped, and I hope you all can help me.

I want to install a late-ish (mid-80s maybe?) Suntour Cyclone crank on a bike with 130mm spacing. English-threaded. The problem is, I don't have the matching bb for the crank. But I figured I could substitute something. Pre-1990 Campagnolo square-taper bb spindles don't work in this crank, they bottom out. I haven't tried a Shimano yet, but that's next.

I'm avoiding getting a Phil bb since they are so expensive, but assuming I did get one, which taper do I look for? JIS? And how long should the axle be?

So, my question is two-fold: first, what taper will work in this crank? and, second, how long should the spindle/axle be so that a double-chainring will clear the chain-stay?

------------------- I don't know about the taper issue; my sense from Sutherland is that it doesn't matter much (but I could have misread the esteemed experts). On the spindle length issue, I use a short-cut method that is probably good enough: (1) Install right cup. (2) with bearings, insert longest spindle you can cadge anywhere. Finish assembly with left side, and install right crank, w or w/o chainrings. Now, sight the chainring middle (you're running a double, not a triple, eh?) back to the cogset, and see how far outboard it is from the center of the FW (we would not talk about cassettes on this list...). Subtract that amount from the right side of the spindle length, and you know what you need for that side. Do similar action on the left, but judging chainstay clearance. Subtract to what you want. Now, you have a good shot at getting the right length spindle. By the way, this automatically compensates for the fact that the 130 mm rear spacing "wants" the back cogs out further from the C/L, and you don't have to guess how far up the taper the axle will set. Of course, you still have to find a spindle that won't let the crank slide up too far.

EXCEPT: They don't all have the "cone" ridges on the spindle the same separation from each other (like the Campy units for the helix threaded thick cups have the cones set inboard). And the cones aren't always in the same position right-to-left.

BUT: in my experience, unless the frame has really, really, tight chainstay length, it doesn't matter too much if you're off a mm or two.

Now, let's be honest: my beloved spouse is an engineer, but I still find it easier to keep a relatively large stash of spindles, some too pitted to use, than to explain this crude method to her...

harvey "measurement challenged" sachs mcLean va