For me, the main advantage of using a mtn triple, lets say a 44/32/22 is that with a relatively close ratio cassette like a 9 speed 12-27, you can still have a reasonably low low gear--somewhere around 19 g.i range, and or you can change the 22 to a 20 and get lower (and of course, using 30, 32, 34 etc cassettes will get it lower)
on my 26in bike, in the mid ring, I can ride up to the high 20s kph, even with a 12t. At times I wish I had a 34t but all in all, with lots of stuff on a bike, the 32t ring gets used for the vast majority of the riding time, ie in the 15-25+kph speeds.
I look at planning for a chainring/cassette combo to put the priority at being realistic about the low range you will need for all kinds of climbing situations for a given bike+gear weight, and then also taking into account trying to figure out the range of speeds that you will be going for the vast majority of the time--and having closer cassettes with smaller jumps means it is easier on your knees and legs, and is more efficient.
I would still always want to have at least a 42 ring, if not 44 for the times we get a tailwind, and or slight downhill. Even with my 42-12 with 26x1.5 tires, I can comfortably go along at 40kph, but then I tend to be more comfortable at higher cadences due to having low torque legs and knees.
I used to think that mtn triples were too limiting, but for me anyway, a bike with 40lbs on it means that the 32 ring is pretty much used most of the time on the flats. On 700 bikes, compared to my 26in bike, the gear inches are going to be a bit higher which is nice to extend the useable top speed range of the 32 chainring.
personally I think with only a 34-11 top gear, you would find yourself missing some larger gears, even though a 42 or 44-11 is certainly not considered high (somewhere in the 90 g.i range)
This sounds like good advice to me. I like the idea of lowering the 3 chainrings down to a usable size, instead of using a wide range cassette. I'm always shifting to find a good cadence. But some riders don't care so much about cadence.
Here's a 22-32-42 with a 9 speed 12-25. Each of the three chainrings has reasonably close shifts.
And the same 22-32-42 with a 11-32. Wider gaps between shifts, especially above 15 mph, where close shifts are helpful.
Here's the
Mike Sherman Gear Calculator settings for the
22-32-42 and 12-25. The popup message is telling you that you can bookmark these settings to recall later. Changing cadence or gear sizes will update all the charts on the fly.
Lowest gears
3.0 mph on the low gear 22-25 is
44 rpm. And with a 22-32, it's
55 rpm . For long, steep climbs with a heavy load, that 18 gear inches on the 22-32 might be necessary. The 22-25 is 23 gear inches.
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To compare: The 22-36-48 and 12-36 mentioned by
acantor above. An interesting setup, too. Very low gears, 3.0 mph is 62 rpm.
