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Double to triple - rear der question(3 posts)

Double to triple - rear der questionMazinger
May 23, 2003 5:06 AM
I've posted before about switching over to a double from a triple. I left the original rear derailleur.

I was looking through some bike specs and noticed that doubles came with the short cage and the triples a long cage.

I have a minor problem with chain rub that I can live with, but was wondering if the rear derailleur type had something to do with the chain rub problem.

Anyone have any comments? Thanks.
re: Double to triple - rear der questionjimmy320
May 23, 2003 5:55 AM
That long armed cage really is just to deal with the extra chain slack a triple crankset makes--about 22 links typically instead of the 14 or so a double creates when shifted largest to smallest ring--isn't always crucial to have the long one depending on your cassette--a close ratio cassette often works with a short rear der and a triple--the more range your cassette has the less likely you'll like the way the short one works with the triple crank.

Chain rub is not a rear derailleur problemKerry
May 24, 2003 3:56 PM
Think about it - the chain exits the chainring at the bottom, and a longer cage in the rear doesn't make the compound angle sharper, it might even make it more slack. Because of chain tension, where most people get chain rub is where the chain enters the chain ring (on top). The RD has no influence on that angle.