Re: [CR]small-small and big-big combos


From: NortonMarg@aol.com
Date: Tue, 2 Sep 2003 13:11:23 EDT
Subject: Re: [CR]small-small and big-big combos
To: marcus.e.helman@gm.com, classicrendezvous@bikelist.org


In a message dated 9/2/03 6:56:40 AM Pacific Daylight Time, marcus.e.helman@gm.com writes:


> I know most of the literature says don't use the small-small or big-big
> combinations. Doesn't this generally refer to triples and/or modern bikes
> with wider spacing? I would think that on bikes in the CR timeframe, with
> double chainrings, cross-chaining would not be as big of an issue, unless
> the chainstays were really short.
>
> I only have 12 speeds, I'd like to use them all.
>

The first thing you should do, is take a look at your chainline. I used to have a preference for having the cranks a little farther "in" than perfect, as I was more likely to use the big ring, 2nd biggest cog a lot. With the chainline in a little I could also use the big/big combo for short stretches if necessary (but never very often). With the chainline favoring that direction, if you use the small/small combo, the chain will drag on the big ring starting with the 2nd smallest gear. If your riding style favors the small ring and smaller cogs, you might think about setting the cranks "out" a bit more than perfect, but you'll lose some performance in the big/2nd biggest position. If you have a 10 speed, you really only get to use 8 gears, if you have a 12 speed, you only get 10 useable (otherwise, you wear it all out, a LOT faster). For that reason, you want to map your gears on a gear chart and make sure you don't have any silly duplications in useable spots. That said, if you have a size gear that really works for you in the area that you ride a lot, it can make perfect sense to have that gear available on both the large and small ring.
Stevan Thomas
Alameda, CA