Originally Posted by
pacificcyclist
Wow.. I suppose my touring double Masi is the exception here with a 42T/24T and 11-36. Transitions are smooth and choices are right. I was equally skeptical about this range as well, but the math from the gear calculator suggested otherwise. After last year's tours, I concluded that the range is fine. I own both a triple and a touring double bike so I can compare.
Cheers.. You triple guys are all "always" right!
Please go read what I posted. Your crank is just fine for
you. I wouldn't make those choices. Nor would I suggest your gear ratios
or mine for everyone.
No matter how you want to do the math, however, the transition between 2 front rings that are a large distance apart are is much larger and much less smooth than the transition on a triple with a step in between.
Originally Posted by
pacificcyclist
The gear ratios on the touring double and triple are exactly the same, because it is the CASSETTE that dictates spacing ratio requirements, NOT like some people suggested is the chain ring. What the chain ring does is raises or lower gear inches in a specific ratio for the whole cassette range to meet riding cadence. With a double, you never get exactly the same gear inches as a triple because the chain ring sizes are different except the lowest gear, but the variances are around 10 to 16% for the first 10 high and medium gears. You either spin more or less. These are the same variances found if one owns a mountain bike with a triple crankset 42/32/22 and a carbon road bike with a double 53/39 or a time trail with a 55T/42T and he or she does triathlons on it. Millions of people ride different bikes with different gearing ratios and the differences are not so dramatic that people aren't going to ride them.
What's important in choosing a touring double is your preferred high and preferred low gears and the transition point so the jump from medium to low wouldn't be too dramatic and it seemed, both Shimano and SRAM agreed that around the 40T mark is the sweet spot. I like 42T front, but some people like 40T.
It's not an either/or situation. What the front does influences what the back does and vice versa. Sure, if you only shift on the back then the steps between the cassette are what dictate the gear ratios and if you only shifted on the front, the same would hold. But once you start using both front and rear, you
have to take both front and back gears into account.