on 9/26/10 9:45 PM, andrew hill at [email protected] wrote:

> So.. when starting to build my new (to me) Romulus.. what size bb might folks
> suggest to get a nice wide Q?

You have to watch it a bit there - simply swapping in a bottom bracket with
a longer spindle will change your chainline. It could move it outboard
enough to affect shifting.

Spindle length and tread/Q are two separate things.

http://sheldonbrown.com/chainline.html

http://www.sheldonbrown.com/bridgestone/1991/pages/bridgestone-1991-13.htm

http://www.rivbike.com/article/components/cranks

To grossly overstate, most cranks currently available are wide or wider
tread - reacting to the trend towards shorter chainstays of larger diameter.
(MTB cranks seem to be the widest.) This allows the arms to clear the
chainstays, which is generally a very good thing, but does move your feet
wider, which may not be.  They change the angle or outward placement of the
arms, but also place the rings where they need to be for proper chainline.

The generally accepted wisdom is that tread/Q should be narrow, but what
defines narrow to me may not work for you.  Hip width, knees and ankle
angles and all sorts of stuff come into play.  Some folks get on a wide set
pair of cranks and go "Aaaaaahhhhhh!" while others certainly don't.

- J

-- 
Jim Edgar
[email protected]

Cyclofiend Bicycle Photo Galleries - http://www.cyclofiend.com
Current Classics - Cross Bikes
Singlespeed - Working Bikes



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