Tandem Tom

My current project, a 1984 Miyata 610, has , what I have been told, half step gearing. Though I have read about it I still can't seem to get my head around it. But I digress. I am changing to 700c with a 8 speed cassette. IF I change the front chain rings am I correct in my understanding that I will need a new RD?
Thanks!

cny-bikeman

It depends on the difference between large and small on both front and rear, as well as the large rear. Google derailleur capacity. Sheldon has a good discussion regarding choosing a derailleur.

hueyhoolihan

if going to a larger small ring, you probably won't. if going to a smaller large ring, you probably won't. if going to a smaller small ring, you might. if going to a larger larger ring, ah.... you might. you may need a new FD. in any event, if it were me, i'd get the rings and run it, fiddle with it a while then decide if what you've got is workable.

AnkleWork

It's very difficult to understand and there's no reference information online. Maybe try a library.

79pmooney

It's really not difficult to understand. Just means that to go through your gears, say from lowest to highest, you alternate chainrings. To do this , you have steps on your chainrings that are approximately twice the jump between chainrings. An easy example:

52, 48 X 13, 15, 17, 20, 23. From low to high: 48x23, 52x23, 48x20, 52x20 ... 52x15, 48x13, 52x13.

Ben

dabac

Re:half-step
(Never mind if the actual numbers are possible or not at the moment...)
Let's say you have a 20% difference in tooth count between each sprocket, and a 10% difference between the rings.
So you're on the biggest ring and the smallest sprocket, and need an easier gear.
Drop a ring and you're at 10% easier gear. Next shift lighter, you shift one sprocket (20% easier) and back up one ring(10% harder) leaving you at a total of another 10% easier.
Mainly used in the era of freewheels, pretty much the only way to a decent range and usefully big steps with few sprockets.

fietsbob

A road Front may work .. Triples now have a deep back plate so You have to set it high to even shift to the outside ring.

, though the granny 3rd may cause chain drag across the cage Bottom ..

My Old SBI Expedition shipped 48-44-28 with a 6 speed freewheel ,, 13-30 outer got the 10's middle got the 5's

asI Vaguely recall ..

RD wraps up the Difference (Big+big)-(Small+small) =

Half step pattern work? Do the math (plenty of charts like Sheldon's do that once you input tooth counts)

rydabent

Once we got bikes with at least 8 sprockets in the rear, the old half step nonsense goes out the window. Even more so with a triple in front.

bikepro

Sheldon Brown's Bicycle Glossary Ha-Hi

Jeff Wills

Ditto. My everyday bike has a nine-cog rear and three chainrings: stumppuller, riding casually, and the red mist. I tend not to change chainrings on any particular ride unless I'm doing a lot of climbing and descending.

bud16415

Some of us don’t feel that way. There is logic that can be applied a lot of different ways. For certain types of bikes like loaded touring bikes where a large range of gearing is required and still a desire for small steps of adjustment a true half step can work out perfect. Likewise heavy riders or not as strong of riders can benefit by a large spread of gears with smaller steps. I also feel anyone that rides in a location where they encounter the full gambit of hills and mountains and flats with winds and wants to ride without compromising being in a close to perfect gear for the job could still benefit from a new version of half-stepping.

The common old road bikes had a 52/42 setup with or without a granny and most people called that a half step but it was really a one and a half step. I run a 45/42 that is a half-step against a 9 speed cassette and get 15 distinctly different gears with no duplication on a triple crank with no cross chaining the range is between 31 and 101 gear inches just on the 45/42. I selected my granny size to give me 6 distinctly different gears with duplication to overlap the lowest two of my 45/42 normal riding gears. So the granny gives me a range between 18 and 36 gear inches.

For me I can spin up anything that comes along with the granny and having 15 gears in the half-step for road riding it’s as smooth as I could ever ask for. I might add that a true half step shift in the front is as smooth as a one step shift in the back.

I wouldn’t call half step nonsense at all living in an area where a wide range of gears is needed. If I lived in a flat place and all I was dealing with was wind sure I would have something with a close cluster of 8 or more cogs in the back and one or two rings in the front.

This is my half-step gearing 45-42-24 X 12,14,16,18,21,24,28,32,36 and I love it.

FBinNY 

Two questions one at a time.

Half step gearing refers to a set up where the percentage jump between chainrings is roughly 1/2 of that between adjacent rear sprockets. For example if the cassette is 12-14-16- etc. each step is in the 15-17% range (2/12 or 2/14, etc), so a half step arrangement would have chainrings like 46-50, which involve an 8% or so jump. I won't get into the logic or merits, because that would mean a long debate, and the right answer depends too much on the specifics.

As for whether you need a new RD, that depends on the new gear range, not the old one. Short cage RDs usually have a take up capacity of 27t or so (sum of big+big minus small+small). So that would be enough for something like 39-53 with 13-26. So if your new gearing falls within that range your original short RD (if that's what you have) should be fine. OTOH if you go with 39-53 with a 12-32 cassette or a triple, you'll need a longer cage RD.

Retro Grouch 

You might find that you need a new front derailleur too.

What size are your current front chainrings? 52/48 used to be a common half step set up. If your chainrings are that closely spaced, and you convert to a 52/34 compact double for example, you bight find your existing front derailleur won't cut it.

davidad

With 7sp you can get half-step. I have it on my touring bike. The cassette is 11,13,16,19,23,28,and 34 which is a 20% spacing. The front rings are 20,40, 44 for a 10% spacing on the two bigger rings. The small ring is a bail-out grandpa gear.
The setup gives 10% spacing between the first 14 speeds and adds 3 more in the low gears.

3alarmer 

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AnkleWork

I guess that's good to know. Neither I nor the OP ride seven speeds.

dave42

of course it would work for 10 speed, or 9, or sram 11, or 8, or 5, 6, 4, 3, or 2, for that matter. I'm keen to try it. Mainly cause i like a straight block, average 7% jumps. Now, to have that with climbing(touring) gears and a high enough top gear, half step looks pretty good.

dabac

I spend some time considering a set-up consisting of a 3-speed IGH, chain tensioner and a quad front. With a careful selection of rings, that would give 12 unique gears about 5-6% apart. Looked nice on paper.
Never got around to build it though. Figured out a way to replace the hub in the Tuffwheel-like wheel I was working on instead.
Would have been an extremely obscure bragging point and conversation starter otherwise: "I have a bike with quarter-step gearing".

bud16415

I agree and in a way like in my case if I could have a straight block of 15 cogs and had a need to go from one end to the other there would be 14 shifts to make. With half step on a 7,8or 9 that doesn’t mean you have to run thru that pattern. You just jump across to where you want to be and then if you need an in between gear you have it. Actually with half step and even though I have it on my 9 speed anything over 8 speed isn’t really buying you much.
Back in the day a 10 speed bike with 5 cogs had some pretty big gaps to fill in and without half-steps you really would have been left wanting. Now half-step really is for fine tuning.

An added bonus to a triple with half-step I have found is the straightest chain line on the tallest gears that are still in my range of usable. The smoothness is something I really like when I get to use them.

cny-bikeman

The thing about miniscule steps in gearing is that to be a benefit one would have to shift more often, which entails a cost of efficiency lost during shifts and adds an annoyance factor.

rydabent

For years I rode a bike that was a 10 speed with the 2 chain rings in front. I never did buy into the nonsense of half step with its double shifting. IMO maybe professional racer "may" benefit, for a casual rider like me it would be a nusance. Now with my 8 and 9 speed cassettes in the rear, I do as other do with the triple up front. Small ring uphill, middle ring for most riding, and the big ring for down hill and or with the wind. I then shift across the gears in back. Why complicate such a fun thing as cycling.

HillRider

Half step (usually with a granny ring) did make sense in the 5 or 6-speed era if you used a freewheel with a wide range. It was the only way to get reasonably small steps between gears and the double-shift requirement was something you learned to put up with. With current 9, 10 or even 11-speed cassettes, it's harder to justify.

bud16415

I agree that’s why I said even though I have a 9 speed cassette I feel 9,10,11 or more could be pushing the idea of half-step closer to absurdity. What is the definition of miniscule in gearing steps? Ask 100 people you will likely get 100 answers. I know a guy that’s a masher and he feels one gear is all anyone should need. Some could make a case for loaded touring a 8 sp setup could be more robust compared to a 10. I don’t know if that’s true or not.
Because my gearing started out as a 9 sp I think I was on the cusp of the gearing logic. I really had no use for my big ring except two taller gears one of them I didn’t have the legs to ever drive unless going downhill and going faster than I felt comfortable going. I experimented with making both rings smaller keeping a 10 tooth difference and all that did was give me a lot of low gear overlap with my granny I didn’t need and it put half my normal gearing on one ring and the other half on the other. In that way it did exactly what you said “one would have to shift more often, which entails a cost of efficiency lost during shifts and adds an annoyance factor”.
So my answer was at first loose the big ring altogether as the steps were just a little more than miniscule for me. It seemed to be a waste losing that one taller gear I sometimes used though. It was then I remembered half-step and saw that a 45t would complement my 42t and give me two rings that are virtually the same one being a gear higher at the tall end and the gear I wanted to keep as my final gear. If I’m riding the flats with mild changes I can pick ether ring and be happy on it all day. You could even say I have a backup chain ring. I even have to look down as I forget what ring I’m on.
The more I rode it the more I found the “halves” to my liking so for me the steps are minuscule but not so small that I don’t notice them when I feel the need.

A good analogy for me is golf. When the game was invented each player would carry 3 or 4 clubs. As a kid I played with a set that just had odd numbered irons and that seemed to be enough. Now I play with 14 clubs. The same swing with the same effort results in about 10 yards of distance difference instead of 20 yards.

ThermionicScott 

Judging by the people I ride with, you can never shift too often. And electronic shifting could simplify half-step into an easy linear sequence, if someone were motivated to program it.

Retro Grouch 

I think so too. I find that I like really closely spaced gearing when I'm riding someplace flat but I prefer more widely spaced gears in the hills.