Tire update: the Pasela 38c has now grown from 34,5 to 36mm width since friday evening.
Originally Posted by
cyccommute
Going from a triple to a double doesn't really "simplify" anything. You still have a derailer to deal with and all you have is one less chainring and less range.
The lower range brings up the other fly in the ointment. If you are currently shifting between the big and middle ring, it means you are using the gears efficiently. Shifting up and down the gear range isn't a "problem", it's the way you are supposed to use the gears.
To me it does simplify things, since with the 38t big ring, it will allow me to stay in that ring longer than I am able to stay in the big ring on my current triple before i need to shift to the middle ring, which means a shift between the chainrings has i been eliminated in more cases than with the triple. This is what i mean by simplifying things.
Originally Posted by
cyccommute
Also going to a 38/24 crank leaves giant holes in your shifting pattern as it does for
all doubles.
This comparison of the 38/24 vs a 46/34/24 crank illustrates the problem.
First, the triple has a wider range so that you don't end up coasting as often. With the double, you end up running out of gears at around 25 mph while the wider triple allows you to pedal for about 10mph more. Running out of gears gets frustrating real fast.
But looking at the shift pattern closely, one of the things that jumps out to me on all doubles is that the transition from the outer ring to the inner ring is large and jarring. Let's say that you are cruising in the 38/19 combination at about 15mph and you feel you need to shift to the inner ring. You'll need to increase your cadence from 90rpm to greater than 120rpm and you won't be close to the cadence you need to maintain the speed. It feels kind of like you've dropped a chain.
On the triple, the step is smaller (although still a bit too large). You only need to increase cadence to 120rpm to maintain the same speed. If you play with the calculator a bit, you can see that a 46/38/24 offers a nice shifting pattern where a change from the outer ring to the middle ring is smaller more natural jump. If you use a 40 tooth middle ring (hard to find), the change from outer to inner is about the same as a change from one cassette cog to the next. I use this on a road triple for my commuter bike and find it a great shifting pattern. A 44/38/24 would be similar but with a bit lower gearing.
First, as said previously in this thread, I dont mind coasting at 25 mph, it is quite a lot faster than my commuting cruise speed, and I would rather have wider range at the lower end. Should I end up finding it frustrating as you and others are warning me about, I can easily swap the ring for a bigger one.
Secondly, thanks for the link to that gear calculator! Thats a pretty handy tool for comparing gear ranges. Up untill now I've been using Sheldon Browns calculator which is not as good for comparing ranges.
Looking at that comparison, I do see what you're on about and it has got me thinking about getting a 26 or even 28t inner ring for commuting, and then keeping the 24t for when I decide to load the racks up. I do not fully agree with you on the drastic increase in cadence when shifting to the small ring, as I always combine it with one or two shifts to a smaller sprocket, to even out the transition between the chainrings.
This whole project is a result of what I like and dislike about my current commuter. Some of the parts are chosen from actual experience, and some are based on what I think will give the result I'm looking for, so the final result of this build, will not necessarily be the final state of the bike - most likely not.