Originally Posted by
Rob_E
It seems like you can get the same range out of a double as a triple, unless I'm missing something. You just set up a double with the same inner and outer rings of the triple, and drop the middle ring. What you lose is the amount of options in the middle. If you like to find tune your gearing for a particular cadence, or if you like to have steady increments to shift through, a triple will get you there. If you don't care as much and just want to make sure you have a low gear for hills and a high gear for speed with a few options in between, a double will do the trick.
I used to worry about this, but I did some calculations and I found that the best combo would be a 40T/26T or 40T/24T for which you will only loose about 2 top gear inches against a stock Sugino SD 600 46/36/26T. You won't notice the difference except during the transition between medium middle gear inches to high low gear inches where you would need to perform 1 shift on the front and 2 shifts on the rear totaling 3 at least in my case. I also have a triple on my Trek carbon bike and if I go down to my lowest 30" gear inches, I have to do the same shifts to get 55" after a steep climb anyhow, but with my touring double, I only do 2 shifts because I planned it that way. Either way, the shifts are going to be different for different people.
I also run a slighty shorter crankset (165mm as opposed to my usual 170mm) so I can concentrate on spinning seated rather than attack retrench method I do with my road bike during steep hill climbs.
2 bikes with 2 different purpose. Carbon road bike for light touring and steel bike with a touring double and a mountain rear cassette for loaded touring.