big chainring 

I rode that set-up for a couple years and really liked it. 52/49 and 15-24 5 speed freewheel. It gave me 8 very nicely spaced gears,

jimmuller 

Tight too. I'm not doubting, but trying to comprehend. Could you actually feel the difference when you shifted the front?

old's'cool

Most of my riding is commuting a 21 mile round trip with payload, at a ~20mph average cruising speed. For me, the 6-8% half-steps (49/52 chainrings) in my cruising range are very worthwhile to have.

big chainring 

Oh yeah. The nice part was shifting the front derailleur was very quick and clean since its just 3 teeth difference. So my gears were like 72,78, 84, 88, 94 inches. But you alternate between front and rear shifts.

noglider 

One problem with half step is that you have to know where your chain is. Another is that shifts can be slow.

Modern (8-speed and up) drivetrains solve most of these problems. Even better would be continuously variable ratios, but the NuVinci hub is heavy and fairly expensive.

Salubrious

Just FWIW there is an Aussie firm that makes 41 tooth chainwheels for the Campy 144 crank: CYCLOMONDO - BICYCLE RESTORATION DECALS

old's'cool

The consequences of forgetting, at least on my setups, are minor. Looking at the chain is generally an option.

Slow, as in up to a few seconds. I make a mental calculation as to whether a double shift is worth it under the circumstances of the moment or not considering how long I'm likely to spend in the selected gear given the terrain ahead, and how sub-optimal the single or no-shift option would be.

Bogester 

I treat my half-stepper (49/44/28) pretty much as a basic triple. The only time I half-step is if I'm hauling a good clip in the middle and I want to up it just a bit...(slight downhill, wind, or to just pick it up a notch). Fairly easy and fast shifts there...always up. I really don't see much benefit to down shifting that small amount and if I'm in the big ring and want to go higher I just shift the rear to the next cog. It's kind of nice to have but in reality doesn't get used too often. Here's mine.

noglider 

Geoff, whether the speed of shifts matters depends on the kind of riding you're doing. If you're tooling around or taking a long, leisurely ride, it doesn't matter. If you're racing or in a spirited club ride, fast shifts make a big difference.

I have downtube shifters on my McLean, which were the fastest shifters in the early 80's. Anyone who races with them today will surely not win. It is a critical difference.

jimmuller 

This is an important point, for it is yet one more reason on my long list of reasons why I don't race or do spirited club rides.

Oh, wait, I think I have that one already. Never mind.

noglider 

I know you're older than I am, but it occurred to me that the more I do about my overall fitness now, the more benefit I'll reap when I'm old. That's why I want to get stronger than I am, even though I'm already in decent shape. I never worked on speed before this year, and I'm 53 years old. Suddenly, racing bike technology doesn't seem stupid to me, even though I doubt I'll ever win a race.

Lenton58 

I've been following this thread with interest.

My Gazelle build is proceeding at a glacial pace due to little but constant issues. But, from the start I intended it as an exercise machine for frequent rides on the flat on the river levees and flood plains around Sendai — 45 - 90 minute thrashings. Slow shifting, as mentioned above, is not an issue.

GEARING AS CURRENTLY INSTALLED: 53-42 on an early two prong Shimano 12 - 21 six-cog freewheel (nice and fresh). I am a little worried that I will be over-geared, but I am hoping that the close ratios will give me a nice choice of combinations with a decent chain-line for the optimum cog.

I have to be concerned about the winds that howl out of Mongolia and sweep over Japan. The rivers funnel the winds. My current wider ratio freewheels, such as the common, modern Shimano 14-28, leaves some big spaces that do not really apply to the flats.

I have thought about trying to locate a smaller big ring — like 48T??

Any thoughts and comments welcome

(BTW: BB, Tange sealed; Cyclone cranks with original rings, Sugino 75 RD, early '600' freewheel, DiaCompe reproductions of racheted, SunTour "Power-shift" )

jimmuller 

I use 47T-42T on my Masi but I've got a wide-range 6-speed FW, excuse me, FreeWheel a.k.a. FW, so that the front gives a half step. I can only guess at your FW (12-13-15-17-19-21?) but with your tighter FW a 48-42 ring set would give you redundant gears in the middle of the range. 50-42 looks better to me. But then, with such a tight FW you probably don't need to worry about getting to the in-between ratios. Even so, 50-42 gives a nice 1 1/2-step crossover for a good general range reduction. Maybe more to the point, with that small cog do you need high gears like that? I'm guessing not.

Lenton58 

Thanks for the great advice, Jim. Yes, your guess was right on the mark (12-13-15-17-19-21). I can't ever seeing myself using the 12/53 on my flat routes except possibly for a sort sprint of about 1 Km where I have a shallow descent. The Cyclone (if I remember correctly) takes a 144mm ring which are expensive items around here. I might just try the 53 and see how it works out.

old's'cool

No argument with those statements. I was only speaking from my experience and the of type riding I do. I did mention further up that my main riding is commuting, at a reasonably high average speed. Other than that, I go on solo workout rides or shopping/pubbing jaunts. No group riding or racing, but almost always I ride at my maximum comfortable pace, since I want to get where I'm going quickly, just like everyone else. For me, half-step gearing helps with that. One could argue, that doesn't necessarily make sense for workout rides, but we all know going fast is fun.

Phil_gretz

I'm really glad for this discussion, and that's why I've revived this thread. I now have a 1977 Centurion Semi-Pro that has 5-speed rear spacing and Phil Wood hubs. So, I really don't want to change much. But the gearing wasn't well thought out. 52-42 front (~23%), with 14-17-21-26-32T rear. So there is essentially perfect duplication of diagonal gears. This leaves me with 6 useful gears. I'm pretty convinced that I need to go to 1/2 step on the front, to have in-between gears. The notion of double shifting doesn't deter me in the least. The table below shows the current situation in the left two gear inch columns, and my planned combinations in the right two columns. I'd be swapping the 42T inner for a 47T to get the half step. Take a look at the table, and give me any feedback you think will be helpful.

The crankset is 144 BCD Sugino Mighty, by the way.


[TABLE]

[TR]
[TD][/TD]
[TH="bgcolor: yellow"]42[/TH]
[TD="width: 12%, align: center"]23.8 %[/TD]
[TH="bgcolor: yellow"]52[/TH]
[TD="width: 12%, align: center"]10.6 %[/TD]
[TH="bgcolor: yellow"]47[/TH]
[/TR]
[TR]
[TH="bgcolor: yellow"]14[/TH]
[TH="bgcolor: white"]79.1[/TH]
[TD][/TD]
[TH="bgcolor: white"]98.0[/TH]
[TD][/TD]
[TH="bgcolor: white"]88.6[/TH]
[/TR]
21.4 %[TR]
[TH="bgcolor: yellow"]17[/TH]
[TH="bgcolor: white"]65.2[/TH]
[TD][/TD]
[TH="bgcolor: white"]80.7[/TH]
[TD][/TD]
[TH="bgcolor: white"]72.9[/TH]
[/TR]
23.5 %[TR]
[TH="bgcolor: yellow"]21[/TH]
[TH="bgcolor: white"]52.8[/TH]
[TD][/TD]
[TH="bgcolor: white"]65.3[/TH]
[TD][/TD]
[TH="bgcolor: white"]59.0[/TH]
[/TR]
23.8 %[TR]
[TH="bgcolor: yellow"]26[/TH]
[TH="bgcolor: white"]42.6[/TH]
[TD][/TD]
[TH="bgcolor: white"]52.8[/TH]
[TD][/TD]
[TH="bgcolor: white"]47.7[/TH]
[/TR]
23.1 %[TR]
[TH="bgcolor: yellow"]32[/TH]
[TH="bgcolor: white"]34.6[/TH]
[TD][/TD]
[TH="bgcolor: white"]42.9[/TH]
[TD][/TD]
[TH="bgcolor: white"]38.7[/TH]
[/TR]

[/TABLE]

Thanks, Phil

gugie 

+1. Back when the only choice was a 5 speed freewheel, half-step + granny gave you the best compromise between range (high to low) and % spacing. Engineers loved them, it took a degree to figure it out. well, not really, but there were no online gear calculators or calculators, so you had to do some real math to figure it out. The gearheads recommended writing out the combinations in order on a small piece of paper and taping it to your handlebars. You used it like rookie NFL quarterbacks with all the play calls taped to their forearm until you had it memorized. Every other shift was one in the front, one in the back, a real hassle.

With modern 8,9,10 or 11 speed cassettes you don't need it anymore.

Pretty much the only value is with if you're keeping a 5 speed rear cluster, maybe 6.

ThermionicScott 

Sheldon's tool is great, but I've really become a convert of pages like this that give more visual output.



Ah, there we go. Looks great to me -- those freewheels that increase each cog by an additional tooth are perfect for half-stepping.

Phil_gretz

So, in my situation would you do it as proposed? Or something different? PG

gugie 

If you can live with the slightly higher low end, I'd say your proposal makes sense. The only reasonable improvement would be to go to an 8 speed freewheel, but that would involve getting a longer axle. Phil Wood can do that for you if you're interested. You'd also have to spread your frame to accomodate. Some cringe thinking about that, but I've done it on dozens of frames over the years, as long as yu get someone experienced to do it, not that big a deal. I'd cost out that second option if you're interested. With 8 or more cogs in the back you use the front chainring a "low range" and "high range" and don't worry about combinations. I believe you'd need a new chain as well, but 8 speed compatible ones are inexpensive.

Those Semi-Pros are beautiful frames, BTW, but you already know that. Got a picture to post?

RR3

I used to run a triple with 24-45-50 rings and a 13, 14, 17, 21, 26, 32 freewheel.

If I was doing very heavy loaded touring in mountains, I would have 40 and 45 big rings.

It was not until 11 speed cassettes that I found similarly sweet tight gearing.

old's'cool

You really can't do any better than that with a 14-32 5sp cluster.

Guilty!
My optimum combo, based on integer #s of teeth (let me know when that constraint goes away ) and available parts is 52-49-36 // 13-14-16-19-23-28. I'm not looking for half-step over the full range, only the cruising/sprinting range where it matters, for me approx. 70-100 gear inches. So the bigger jumps at the low end of the cogset reduce the need to shift into and out of the granny chainring. The tighter spacing at the small end of the cogset allows single shifts (say 12-15% steps) to be quite workable for undulating terrain; double shifts being reserved for longer cruising stints or when necessary to reconfigure for starts/stops or prolonged uphill/downhill. There is no need, indeed no excuse, for cross-chaining with this combo.

jyl

It would be interesting to combine programmed electronic shifting with half step/granny. You'd simply push the lone shift button "up" or "down", the electronics would figure out what combination of front and rear shifts to give the next higher or lower ratio. No need for the expensive, short-lived 11 speed chain or the excessively dished 11 speed wheel. Of course there would be a big jump to the granny, but I am convinced that when a rider reaches down to his 36 G.I., he usually doesn't care too much about small steps.

ThermionicScott 

One "future project" of mine has been to dust off one of the "E" cassettes in my collection, and put together a 45/42 crankset for it. A very suitable 40-100" range with nice steps, and no cassette modifications needed!



Of course, I'd use just the right BB spindle length so that I could cross-chain the small/small to allow every gear on the top end.

old's'cool

To each, his own poison!