Originally Posted by
bud16415
We basically have the same desired range and also feel a 42t is a good gear for us as our starting point in the center of our wide spaced cassettes. Yours being 11-36 (10) and mine 12-36 (9). I was curious as to what my triple would add to your double so I ran the numbers. Of course we both have the same granny gear a 24t so that won’t change we are both the same there.
Below are your gear inches with the 42t and below I added in the ones you would get if you had the second big ring. Of course you will get one or two higher gears with a big ring but I did the 42t,45t to see what the half step range would be. The additional gear inches are shown in ( ).
I know the ring positions are different on a double than a triple but in my case the chain line was a big factor on the (80),(92),(109) GI. Likewise on the triple the line is very straight on the center of the cassette cogs and those are some common used gear inches.
31,35,40,47,53,59,66,75,86,102
31,35,40,47,(49),53,(57),59,(63),66,(70),75,(80),86,(92),102,(109)
Without changing anything in your gearing you have now except adding the weight of a ring you could have 7 more gears and a much closer spacing. If your spacing now is sufficiently close then all you would get is the 109 GI and if you never have a need above 102 GI and you don’t have any issue making the 24t to 42t shift then the simplicity of a double outweighs the advantages of the triple.
Yes, I have thought of half stepping with a triple and was something I had done in the past. I found that in order to get 7 more gears, you would have to double shift often using your front derailleur and rear. And usually I have to bring a gear chart with me to really know which gears I should be in as my other 3 bikes do not do half-stepping. Since I don't ride this touring bike often unless on tours, it's not something you would automagically remember operating in. Besides in touring, most of the time people shift gears based on pedal feel, not some gear inches number you must be in. I found that with that setup, I rarely use what I thought was a perfect setup. I usually end up cruising with only 3 gears, 2 of which aren't even in the half-step arrangement. I would love half-stepping in the lower gears because I tend to usually spin out in too easy gears and then spin with effort in too difficult gears and wanting something in between, but you can't do that as effectively between 110BCD and 74BCD. But what we are talking about is the finesse of a triple crank.
3 years ago, I met a guy who was touring the Rockies and ended up on the ferry to the San Juan islands. He was riding a normal touring bike with 54 gears! His setup is perfect, because he's got slightly narrow 11-26 9 speed cassette giving him a 10% differential mated to a Schlump mountain drive front IGH and a SRAM Dual Drive 3 speed IGH rear hub giving the ultimate high a 111.6" and low of 19.6" with an even spacing of 10%. Even my triple mountain crank of 42/32/20 on my full suspension touring bike then was no match. I said hi and ofcourse was admiring his setup and was trying to start a conversation of where he went and how he enjoyed the Rockies. But then he goes into the gear debate between his 54 gears where he claimed he could only tour on in the Rockies as anything less would be inferior against my 24 speed bike. I sensed a gear head debate coming and kindly walked away. I didn't want nor need to embroil myself into a gears pissing contest of whose got the best setup.
This discussion seemed to be angling towards that.
