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Triple to Double(4 posts)

Triple to DoubleAET
Sep 14, 2001 12:51 PM
I'll be buying a new bike soon and will likely be going for the double chainring.

i am not a great climber so if my bailout gear is 30-25
on my triple what should i have on a double if the small chainring is a 39? btw, i don't really need the 30-25 but
i fear 39-21 my be a bit hard on me.
It sounds like you're running ShimanoCliff Oates
Sep 14, 2001 1:11 PM
A 30-25 ratio is 31.5 gear inches. The best you're going to do with a standard Shimano road double is 38 gear inches (37 if you swap the standard 39t small ring for a 38t ring) using a 12-27 cassette. I believe I've read of people using up to 30t cogs on MTB cassettes with standard Shimano road double derailleurs, but I'm not a Shimano guy so someone else would have to address the specifics of that.

FWIW, you might want to play around with the gear calculator on Sheldon Brown's web site.
re: Triple to DoubleChen2
Sep 14, 2001 3:11 PM
When I went from a triple to a double I chose the 12-27 rear cassette and standard 53-39 chain rings (Dura-Ace). This set-up is ok for me, I'm 58, 165#, with bad knees, and ride some significant hills, but not mountains. If after you try the 12-27 you find you need lower gearing you could replace the rear cassette and rear derailleur with XT or XTR 12-34 (mtn.gears), but the ratios will be really wide, you'll be missing the 13, 15, 17, and 19 cogs that you may need for the flats. If most of your riding is in mountains that might be a good choice, but I would try to stay with the 12-27 instead. With a double you could replace the Shimano chain rings with TA rings that might fit your needs better.
re: Triple to DoubleAET
Sep 17, 2001 5:30 AM
thanks. will look into all that.