RoadBikeReview.com's Forum Archives - General


Archive Home >> General(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 )


Used to a triple - getting a double(8 posts)

Used to a triple - getting a doublestan_b
Oct 3, 2002 7:04 AM
My current bike has a triple which I am reliant upon for mountain rides. I am planning on buying a Jamis Eclipse which only comes in a double and asking them to install an 11x27 cassette in back to compensate.

Does anyone have experience in how a 39x27 gear ratio compares to the 30 tooth ring on the triple?

Thanks!
how about lx or xt rear der with a lower-geared cassette? nmJS Haiku Shop
Oct 3, 2002 7:12 AM
You can compare in "gear inches."cory
Oct 3, 2002 7:18 AM
Gearing's measured in "gear inches" (there are other ways that make more sense, but that's the standard). To calculate, divide the number of teeth in the chainring by the number in the cog, then multiply by the diameter of the wheel in inches (use 27 for a road bike, 26 for mountain).
Example: 23 (cog) goes into 30 (granny ring) 1.3 times. Multiply by 27 and you have about 35 gear inches. A 53/39 double with a 27-tooth rear cog would be 39 gear inches.
You can use this to find a gear on your current bike that's equivalent to the new low you'll have on the Jamis to see if you can live with it.
ring ringStarliner
Oct 3, 2002 7:19 AM
A 39x27 would correspond to a 30x21 on a triple.
what about a 39x32? 39x34? nmJS Haiku Shop
Oct 3, 2002 7:28 AM
24.6 and 26.2 nmcyclopathic
Oct 4, 2002 9:35 AM
Go Chorus 10 w/ 39/29 for 1.34 ratio. Like 30/23__ NMSpunout
Oct 3, 2002 7:42 AM
or Centaur ...tarwheel
Oct 3, 2002 8:37 AM
I have a Chorus 10 group with 13-29 cassette, and I haven't found a hill yet that I couldn't spin up in the 39/29 combo. I got the group for that reason because I didn't want to deal with a triple. Centaur is about the same price as Ultegra. Be aware, however, that Campy maintenance costs are much higher due to the ridiculous cost of their chains and cassettes.