Originally Posted by
cyccommute
Go run the chart. A 46/36/24 does nave the same range. No argument. But you seem to keep missing the spread. A 46/36/24 has a 28% difference between the outer and middle ring. It has a 50% jump between the middle and inner ring. That 50% jump is highly noticeable when you shift. I find that I have to speed up my cadence significantly when I change to the inner ring. But, since I usually do it when I'm starting a climb, the bike slows quickly and my cadence comes down to a more comfortable rate.
But for a 45/28, there is a 60% difference between the two rings. You also commented above that
With the pattern of the compact double you are using, you have not just a double shift to smooth the transition from ring to ring but you have do a shift off the outer ring and shift the rear 3 times to get to a gear that isn't 60% different from the one you were in. For example, say you were riding in the 45/24 combination (a 51" gear) and you had to downshift. You could drop straight to the inner ring and you'll be riding in a 31.5" gear. The next gear closest to the 45/24 combination is the 28/17 or 3 upshifts. On the other hand, with the 46/36/24 7 speed, you could be riding along in a similar gear of 46/24 (52" gear). If you shift off the outer ring to the middle ring, you end up in a 41" gear. It might not be the best gear but it's not a 60% change. The change is smoother without double shifting.
I have no problem with you riding whatever you want. But you can't just look at the overall range of the cranks and say that they are just the same. The math just doesn't support that statement.
Hmm, I did run it through Sheldon Brown gear calculator site based on a 700x38c setup and 170mm cranks.
Below are the gear inches for 46/36/24 with a 7 speed K 13-34 cassette (on my past Norco Alteres)
(46) 96.7,83.8,73.9,62.8,52.4,43.3,37.0
(36) 75.7,65.6,57.9,49.2,41.0,33.9,28.9
(24) 50.4,43.7,38.6,32.8,27.3,22.6,19.3
Below are the gear inches for my 42/24 with a 10 speed 11-36 SLX cassette (on my current Masi)
(42) 104.3,88.3,76.5,67.5,60.4,54.6,49.9,44.1,35.9,31.9
(24) 59.6,50.4,43.7,38.6,34.5,31.2,28.5,25.2,20.5,18.2
Notice that on the lower gears, my 2x10 11-36 is superior than the 21 speed 3x7 setup due to the 7 gear spacing on the 7 speed cassette, which is providing the wider gear ratios.
Typically, riders shift BASED on pedal feel not on some strategic gear chart formulation. If the pedal becomes harder to push, they shift down a gear until they can't shift and then they shift to the next easier chain ring. You made it sound like every cycle tourist shift gears like a pro Tour De France rider or Michael Andretti driving a race car. Most cycle tourist do not attack a hill like a fast roadie would do. Yes, some do this but this is not the norm.
With the 21 speed 3x7 setup, they will have to shift 2 times to get to the granny 24T, whereas with my 2x10 system, I only shift 1 time.
Is there a reason why I would want to shift from a 42/19T (60.4") to a 24/11T (59.6") just so that I get a nicer ratio?!?
If you examine my 2x10 gear chart, it has just about all the gear ranges of a 3x7, except the middle to lower ranges have a tighter cluster of the 10 speed.
Even if I shifted to my lowest gear inches 42T/36T (yes cross chaining) which is 31.9", dropping it to a 24T would simply put me on a 18.2" gear, hardly causing me to fall over face flat either. Did this a few times this year in this combo no problem climbing grades starting from 4% going up to 20%+ on Saltspring Island in British Columbia. Usually, I bail from 44" gear when I know there's a tough climb ahead to 25" and then spin and then shift down when it's necessary. Again, I see your point where I will have a 60% gear inch gap, but that's toward the end of the lower gear ranges, something I don't mind bailing to. It's called granny gears for a reason! I have a working double bike and a triple bike with similar gear ratios and I just don't see a big difference in gear shifting. My setup is based on a stock 7 speed touring cassette and a 10 speed SLX cassette (both are available stock) which others I'm sure are using as well.
At the end of the day, touring is about riding the bike and making it work. Most people ride with a standard crankset modified with a 26 or 24T granny off their 52/42 or 46/36T trekker cranks and they did just fine on any terrain. Everyone always want more gears. The guy who has 54 gears wanted even more because he thinks he needs more just the same as everyone here in the world would love to have more money.
You can tour with a triple or a double and as long as you have the highs, medium gears and enough lows to climb Mt. Everest, then the issue here is what do you prefer to have. Triple or double.
But I think some people really misses the real point and that is, a triple crankset was conceived to open up the biking interest to a wider audience by bringing in "LOWER" granny gears for people who don't have the muscles to pump up a hill with a 53T/13 or 55T/11T. In the 70s, the lowest acceptable granny was 27". See how times has changed this. Bikes today have lower gears thanks to the compact double, mountain trip and the new mountain road gearing from SRAM and the technology is there to be used. Some people insist to be luddites in the triple era and that's fine. Some of us are just making aware that you can have a double setup with lower gears and decent highs for touring. Ultimately, it's the rider who chooses the system.
Cheers.
