Please explain half-step plus granny gearing?
 

Why would you run a 26/46/48 triple? Is it because with only 5 gears on the rear wheel, you would switch between the 46 and 48 on the cranks to keep the ratios closer together and just use the 26 as a bail out gear? Is that why this set up has pretty much disappeared (because with 7,8,9 or 10 gears on the rear wheel, it is possible to have a more consistent close ratio?)???


....wait....I think I just answered my own question....

Right?

Anyway, I think it would make gear selection a lot more confusing. Or at the very least, a lot less mindless. Any one use/prefer this setup?

Here is a recent picture from a CL list that got me thinking about all this:
http://i870.photobucket.com/albums/a...ne_T700_01.jpg

Yep, you got it spot on. And with the advent of 8-9-10 speed cassettes, half-step chainring combos have become obsolete. And hence the rise of the compact double. The only reason I would use a half-step combo is if I wanted to preserve a vintage 5-6 speed freewheel configuration and have closely spaced ratios. Getting those to all harmonize without a couple of redundant ratios is tricky. There's a calculator on the interwebs that helps figure out the required cog sizes and chainring sizes to achieve that perfect half-step gearing throughout your gearing range.

Have you played with Sheldon Brown's Gear Calculator? If not, I recommend it. Most people set it to give results as "gear inches," but it really doesn't matter. Figure it out and get used to it; it becomes a very useful tool.

Enter your chain ring sizes etc and calculate; you probably end up with something like this:

50.1 88.7 92.6
46.8 82.8 86.4
43.9 77.6 81.0
39.0 69.0 72.0
33.4 59.1 61.7
28.1 49.7 51.8

Before you get confused, just ignore the biggest chain ring (third column). Now, looking just at the first two columns, and noting that two of your gears measure 50", you basically have eleven distinct gears; let's pretend they're evenly spaced, and number them as follows:

6 11
5 10
4 9
3 8
2 7
1 6

To this you can add the biggest chain ring for half steps, i.e. 6.5, 7.5, etc. Though, frankly, changing back and forth between a 46 and 48 chain ring is quite a bit less than half of a step.

Bike cad has a handy function in which it displays the gear inches (or ratios) in a handy graph.

When I set up my PX-10 in 1980, I found it really useful to do the math manually (pencil and notepad). I learned a lot in the process, and got the gear choice correct.

http://i120.photobucket.com/albums/o...d/IMG_1628.jpg

Great running gears.

http://i120.photobucket.com/albums/o...d/IMG_1624.jpg

http://i120.photobucket.com/albums/o...d/IMG_1626.jpg

Someday, I'm gonna have to try one of these new fangled compact cranks on a 10 or 11-speed rear end!

:D

LL, is that a short cage Cyclone taking up 24 teeth on the front and I would guess 13 on the rear?

Half step plus granny here too...BIG gears...

http://home.comcast.net/~khatfull/images/tsv/ag1.jpg

And the gearing...

http://home.comcast.net/~khatfull/im.../aggearing.jpg

I basically have a 14 speed...the only combinations used on the 28T chainwheel are 28/28 and 28/38. It's not perfect half step but it's close and I used the cogs I had available when building up the freewheel.

Here is a Wikipedia explanation:

Half-step gearing

This style is not available off the shelf. There are two chainrings whose relative difference (say 10%) is about half the relative step on the cogset (say 20%). This was used in the mid-20th century when front derailleurs could only handle a small step between chainrings and when rear cogsets only had a small number of sprockets, e.g. chainrings 44-48 and cogset 14-17-20-24-28. The effect is to provide two interlaced gear ranges without any duplication. However to step sequentially through the gear ratios requires a simultaneous front and rear shift on every other gear change.

Half-step plus granny gearing

This style is not available off the shelf. There are three chainrings with half-step differences between the larger two and multi-range differences between the smaller two, e.g. chainrings 24-42-46 and cogset 12-14-16-18-21-24-28-32-36. This general arrangement is suitable for touring with most gear changes being made using the rear derailleur and occasional fine tuning using the two large chainrings.[9] The small chainring (granny gear) is a bailout for handling steeper hills, but it requires some anticipation in order to use it effectively.

Yeah, it actually is the short cage version. I had/have a long cage GT version that I held in reserve. BUT, if the granny was/is truly used only as a bail-out in the largest 2 cogs only, I never had a problem. In return, I had the faster and smoother feel of the short cage Cyclone.

Note also the rare Cyclone front with the added triple-ring lower reach. (Dunno what it is actually called, that addition?)

Sadly, I sold the frame here on BF last year, but I still have the drive train. The Cyclone is doing temporary duty on my '85 Mercian. And the sealed OMAS BB is awaiting a (long, long overdue) frame.

While it's nice that 8- and 9- and 10- and 11-speed have made half step gearing unnecessary, it seems to have created a new problem. Or am I wrong?

The problem it solves is having to do a double shift (shifting both derailleurs) to get the gear you want.

The problem it creates is the work it takes when going from one chainring to the other. Or does it? I haven't used a compact double yet. The two ranges are either completely or almost completely non-overlapping. So I would go from small-small to large-large in the middle of the total range of gears the bike has. Or does it not play out that way in practice?

My favorite setup among my current bikes is a single step plus not-quite-granny. I.e. the cogs are 13-14-15-16-17-19 and the chainrings are 36-48-52.
I have all the range I need, and hardly ever have to double shift. The only exception would be on a long hill where a double shift is worthwhile to get an optimum ratio. My next favorite setup is a half-step no granny, which is 13-15-17-20-24-28 and 48-52. Slightly more range at the low end than the other setup, but more double shifts required to access the optimum ratios for cruising. Since this one is SIS on the RD, that almost negates the disadvantage of double shifting.
As for most of us, I suspect, some of the constraints on truly optimizing each bike are cost, and keeping things somewhat period correct, not to mention time & effort searching for the ideal parts.

i've been shifting a 48/32 crankset up and down with no problems. Using a front mech meant for a double to boot, so no taller cage to aid in pushing the chain. I won't claim the upshift is as smooth as a 52/42 for example, but it certainly isnt a problem.

Dunno about anyone's favorite, but here are the rules for half-step. First, the tooth ratios of adjacent pairs of rear cogs are the same or nearly so. Second, the ratio between the two chainrings is half the average cog-pair ratio. If you look at the Sheldon Brown table for Khatful's amazing wide range system, you can it's ratios are nowhere near the same - it's not a HSG. And it's result is that he does not get all 14 speeds free of duplication. A real half-step will not give you any overlap. That's why for a 2x5 setup of yesteryear, it was desireable.

I understand it's not true ratio-based HSG. But the concept is still the same....wide range between rear cogs close chainrings.

Due to RD capacity issues I know that I lose the 28/13-15-18-22. However, the remaining 14 ratios are fairly evenly spaced, obviously the jump from the 28-38 cogs is big and outside a real HSG setup. Much is it too has to do with availability of cogs...I split several freewheels to get these.

All I know is that I don't want for a gear to pedal in :)

EDIT: If I had cogs available, this would be much closer to HSG:

http://home.comcast.net/~khatfull/im...aggearing2.jpg

A nicer interactive alternative to Sheldon's calculator is here:

http://www.gear-calculator.com/#

You can calculate much more quickly and visualize what size rings you need to achieve true HS gearing using nice visual sliders. And what else is nice is that you can save custom configurations as their own URLs. Like this one: check out this PERFECT 2x6 HS setup I came up with:

http://www.gear-calculator.com/#KB=4...5&UF=2099&SL=3

Interesting! Looks like a nice tool for those who use modern equipment. No 3, 4, or 5 speed hubs are included.

With 48/33 rings, the Huret FD I'm using makes really smooth shifts; remarkably so. In my experience, I don't need to shift and go through gears in any structrued fashion. My large chainring is right near centered with my 7sp freewheel and I can use all 7 cogs with that ring; though I probably don't use the 48-28 combo much. So, yes, I could continue on a pretty even increase/decrease in gearing steps with a double shift. But, in practice, that's just not how I'm using it. I stay in the 48t ring. I may be climing in the 48-24, then just dump the chain onto the small ring for a 33-24 and change my cadence. I don't know, I don't really think about it all that much. I setup my gearing so that my big/small combo gives me a fast enough gear and the small/big combo gives me a low enough one. If there are 8 cogs in between that, that's nice. If there are only 5, then that'll work.

http://gallery.me.com/justinhughes/1...13173029410001

This particular setup (crank and deraileurs) probably weighs a good bit less than a half-step plus granny setup such as Keith shows.

http://gallery.me.com/justinhughes/1...13171441360001

Wow... Keith, that is a seriously LOW gear. When things get steep enough to require something that low, I imagine needing a pick and crampons more than a lower gear... :thumb:

Half step will drive you nuts if you live somewhere with constant rolling hills. Way too much front shifting.

Here's my somewhat extreme example.

http://farm7.static.flickr.com/6160/...5aa20dfb20.jpg

Click here for more details.

hmm, you got away with a short cage derailleur on that setup? That's promising.

It's probably pretty stretched in the 48-28 combo, but I haven't had any issues yet. As I said, I don't use that combo much; maybe never. I had a long cage on there for a while, but it wasn't necessary so I installed this one. Total chain wrap is 30t with this setup. Disraeli Gears indicates this RD has a max wrap of 31t. It shifts the 28t cog with no problems either.

As much as I like this I think I'm going to install 8s Ergos and deraileurs and a 13-25 7s freewheel just to try them out. Has you used Ergos with a randonneur bend bar?

Well, a lot of that-- being driven nuts-- can be alleviated with better equipment. Or I should say, "better-suited" equipment.

Surprisingly, a lot of modern front derailleurs don't deal well with a small tooth gap between middle and outer. Shimano made one specifically for half-step; I like the SunTour Mounttech; and as the Colonel stated, a Huret front works pretty well.

The other thing is that there's too much space between the middle and outer rings for a crisp shift. The chain can sometimes drop between the two, which seriously sucks. The T.A. rings can solve this problem, at a cost. A hefty one. I've been lucky enough to have access to a mountain of spares for mix-n-match, and I've pretty well got my stuff dialed in. But now I'm thinking about going to a 42-46 up front (as I have a Stronglight 93 with these rings mounted) and that would let me respace the Trek to 130mm in the back and use an 11-28 8-speed cassette for 15 pretty evenly spaced gears and only one duplication.


Cassettes and freehubs are such a slippery slope. I'm afraid if I do this I'll be wearing spandex and riding carbon in 6 month's time, and a year after that I'll be gelling my hair and wearing Oakleys, and after that there is just no return from that bleak bourne.

i have not.

I've used Ergos with a Noodle - EXCELLENT combination, if you route the cables right. I'd have trouble seeing a Rando not working.