noobinsf 

I have been messing around with gear-calculator to decide on initial gearing for the upcoming Mercian build, and I'm curious what folks think now that I've narrowed it down to these two options. I've been collecting cassettes and derailleurs for a while, so the two configurations pictured below are not theoretical -- I have the pieces in hand and can install them.

Here's my main concern -- I like the ultra low gear of the 12-34 cassette because there are lots of steep hills near my house (and I'm out of shape), but there are a lot more direct duplicate gears than with the 11-30 cassette. Would I miss something great by having a 22.2 gear-inch low gear vs a 19.3 gear-inch low? Or would the duplicates of the 12-34 annoy me such that I should avoid it, even if it offers me a lower gear?

Either way, I have a Microshift M55 rear derailleur that will handle a 45-tooth spread, and my front mech is a Suntour XC Pro that can easily handle the 24-tooth chainring difference, so capacity is not a concern with either setup. I am going to mount an IRD Defiant with 48-36-24, so the chainrings are set and will not change. I'm not concerned about having too high a top gear, since it's a single outlier with the 11-30 cassette.

I dunno -- thoughts?

jonwvara 

I doubt that you would notice much difference between those low gears, so I would not worry too much about that.

As always when I look at the gear-chart output for I setup involving an 11-tooth cog, I find myself wondering who decided that the world needed such a preposterous high;

nlerner

I'll admit to not planning out my gearing very well, but one consideration is the gears/cog combos that I'd be riding on most often, not those extremes on either end. Along those lines, I tend to be on 50-65 gear inches for most of my riding, and the second combo above has fewer overlaps and more steps in that range.

Dfrost 

My gearing for our very hilly PNW terrain is similar to your second set, but without the 11T cog: 12-30 8-speed with 46-36-24 rings. I’ve been very happy it with for almost a decade. I used to obsess over gear charts and worry about near duplicates, etc. But in actual riding, what I notice is the progression on a single ring, because that’s how shifts tend to happen. And like @nlerner, closer spacing in the range that I use on flat-ish roads feels great with winds and subtle inclines. So I assemble “custom” 8-speed cassettes with single-tooth steps (when I’m in mid-season “shape”) in the middle, wider steps on the ends: 12-14-15-16-18-21-25-30. Early season when I’m riding more in lower gears: 13-15-17-19-21-23-26-30, same rings.

noobinsf 

This is precisely the kind of thoughtful feedback I was looking for and why I love this forum! Thanks to you all.

52telecaster

Typically I would want less duplication but I like the top end of the 12-34 cassette a lot better. The 12-13 step will be great on long flats. As for the ultimate low the 34 might make u get off a little later but it's not much better than the 30 tooth cog. I used to insist on sub 20 for my low but in my old age I'm not to proud to walk up a hill. Anybody that has a problem with it can just enjoy their superiority.

Also at some point you might think about a different middle ring and you could half step the 12-34. It would be a mighty narrow half step but some folks like it.

SJX426 

I have recently moved from 5/6/7 speed to 8/8/10 speed configurations. I find bigger gaps at the lower gears is more acceptable compared to the middle set. When I climb a hill, I need to be able to get to a usable cadence. When I am cruising with small inclines, I like to have finer resolution to keeping my cadence in the range of 75 -95. Higher gears are used for down hills and even then if I run out of cadence, I am willing to coast. For this reason, I converted from 8x2 to 9x3 with much more comfortable control of my cadence. The smallest sprocket is 13 on the 9 speed with a large chain ring of 52. The bottom is a 26/30, which is plenty low for me. Oh and I do use it upon occasion but typically I can stay in the 42.
I have option of changing rings with 54-50 options for the large and 42/40 for the middle. Playing around with the same site offers little in a good combination to address low and high gearing with good spread in-between.

droppedandlost 

second set definitely. The big gap at 70" in the first set would irritate me every ride.

droppedandlost 

Two different tire sizes?

noobinsf 

You know, I must have changed them between setups and forgot to match them. In any case, the difference was pretty negligible, and it didn't affect the quantity of duplicates or the distribution of gear inches, even if the individual values were shifted slightly. I mostly wanted to illustrate the "point spread," but yes, that's a good catch.

xroadcharlie

I like the closer spacing of the 11 - 30 cassette. But make no mistake, the 15% jump from 19.3 to 22.2 gear inches can be a game changer for long steep hills if you need them, not so much for a short steep one. Just use you past experience as a guide. If you where OK before with 22+ gear inch, I'd recommend going with the 11 - 30 cassette. I think 22.2 gear inches would get you up most climbs without too much trouble, at least without 30 lbs of groceries.

It's mostly the high gears where I want them closely spaced, And both cassette's seem OK there, The difference between 16/14 and 15/13 is only 1%, But the 20 - 17 jump on the 12 - 34 cassette would be irritating to say the least, That's 18%. For very low gears it's fine, but not in the midrange, especially climbing. I don't like the 20 - 23 jump either, but could live with that.

I wouldn't care about how many gears duplicate, as long as I can keep gear jumps about 10 - 14%, and they cover the range I need.

L134 

[QUOTE=noobinsf;22448919 so the chainrings are set and will not change.[/QUOTE]

May I ask why? This seems like an extremely limiting and unnecessary condition unless that crank doesn't have removable chainrings. Slide those chainring numbers around a bit.

noobinsf 

I have been waffling on this build for a long time, and I just need to make a decision and build so I can try out the frame, so on one level, this is just removing a variable. I wanted to address the paint on the frame (which I tackled last year) and build a wheelset for it, and I've tinkered with several "practice" bikes before finally getting to this one, so I'm eager to get it on the road. Also, I bought the crankset as a shiny new triple, so I want to use it undisturbed, at least initially.

I mess with chainrings all the time, so I certainly could. I just don't wanna this time. Also, I don't really know my optimal gearing enough to know what my preference will be, and hearing folks' feedback above has been really helpful in my thinking about how to set it up and ride different terrain, so this is active research anyway.