old's'cool

My preferred half-step plus granny setup is 52-49-36 (36 is the largest chainring I have found on 74 BCD). My grail cluster is the elegant 13-14-16-19-23-28 (six-speed is the highest I roll on my vintage bikes). So the half-step formula really only applies to the 14-16-19 cogs, but that is exactly the range I spend all my time cruising on (assuming nearly level grade, and moderate wind conditions).

Road Fan

Mdave, I think you understand it correctly. If the cog to cog ratios are (by some magic!) all 1.200, then your crank ratio (big divided by small) should be 1.100. Since you tried to match those ideals in your gearing design, it's probably close to really good.

Have you done it? I'd say yes. As Verktyg points out it's impossible to get an exact half-step. I have a little math trick in Excel to calculate how good it is, but I'm not sure it's really worth much. If I was being paid to design say, 5 "most perfect" half-step gearings, I'd use the trick (ok, ok, it's standard deviation).

If you like I'll put your numbers into Excel and give you my take on it. You can PM me info or we can do it out here in public so everyone can see. But you'll have to bring the beer.

smontanaro 

Just stumbled on this thread. I guess I should set up a subscription to the forum so I see new (to me) topics? Anyway...

I'm in the process of building up a 1970 Atala Super Professional which will start out with 47-44 up front and a 5sp 14-28 in back. My hope is to ride it in the Dairyland Dare next month. Might be some walking involved on some of the hills...

Road Fan

Based on my understanding, if you try to follow the math guidelines using a freewheel that already has actual step ratios that are pretty close to equal, that's as good as you can get, and most likely as good as anyone could have got BITD.

I also think that if you follow the math guidelines with a 5-wheel or 6-wheel (or even 7-wheel) cogset you will produce 10 or 12 or 14 predictable gear ratios, if all are built with appropriate chain sets.

The only question is, is that what you want and what you like to ride. Based on what you are saying (want 6 predictable ratios, and larger jumps at the ends), you are not making ˝ steps. I expect you are making good gearings, I just think they are most likely not ˝ steps.

mountaindave 

@Road Fan, did you see my gearing chart on the previous page? Along the bottom is the grear step ratio. The biggest deviation from my ideal 10% is 12%. The rest are all very close to 10%, many are exactly 10%. I too have a little spreadsheet formula that calculates each step and then the deviation from the target step of the two chainrings. It has helped me hone in on what is best for my particular setups. The visual representation of gear ratios is also nice when using the online gear-calculator - a versitile and powerful little tool really.

Good discussions all around, really. I also finally understand what 1.5 gearing is now (though I can't imagine trying to learn it!). Glad I found this thread too. It helped me refine my ride and enabled more geeking out/obsessing over ideal gearing.

jimmuller 

mtdave (and anyone else), the goal of 10% front shift if the rear shifts are all 20% really isn't quite right theoretically. Of course, as has already been pointed out the FW is constrained to have an integer number of cogs so the actual ratios can't be numerically perfect. Which means that getting the gearing close is as good as you're going to get. But here's the problem with that 10% vs. 20% question:

Ideally it should be half but on a log scale, not on a linear scale. If you jump by a factor of 1.1 twice, you end up with a jump of 1.1 squared, or 1.21, i.e. 21%, not 20. To have two jumps give you a final ratio of 1.2 (i.e.20%) you need each jump to be the square root of 1.2 which is 1.09544 or about 9.54%.

Yeah, I know, it's close to 10%. I'm just being stubbornly pedantic.

old's'cool

Wha+s more, big jumps, percen+age wise, are more +o1erab1e a+ +he bo++om of the gear range. It is in the cruising range +ha+ you rea11y want the fine steps. Of course, if you`re a racer, +he defini+ion of `cruising range` may differ from +ha+ of we mor+a1s. Once again, I apo1ogize for +he +yping; my keyboard is gimba11ed.

jyl

Half step gearing was ridden today in the pro peloton. On stage 4 of the Tour De France, the cobbles stage, many riders were on 53/44 or even 53/49.

Tour de France tech: bikes built for the pavé | CyclingTips

verktyg 

Exac+ly....

@Road Fan,

When I was doing my calculations and experiments I used percentages not multipliers and charted my results on graph paper... and no, it wasn't in hieroglyphics!

I originally set out to get 10 usable ratios with 5% or 10% jumps out of a 5 speed freewheel. I began by charting the ratios of the bike boom standard "alpine" 52-42T x 14-28T gearing. There were 2 to 3 duplicate ratios with those setups and no logical progression for shifting.

Some "gear freaks" get or got OCD trying to set up the perfect half step ratios (me too for a brief period).

After custom building a number of freewheels I came up with my 49-45T x 13-26T set up. Eventually I found that at a cadence of 90, close ratio gearing in ~60 to 88 inch range met most of my riding needs. To achieve that I had to sacrifice even spacing in the high and low ranges which resulted in bigger jumps but that wasn't a problem (limitations of a 5 speed FW).

I used mostly Atom freewheels back then and we had most of the sprocket sizes at out shop. Regina sprockets interchanged with the Atom sprockets.



In the mid 70's at my best I could honk up the mountains in New Mexico and Southern Colorado with ~47" gearing - 45T x 26T. The 49T x 13T combo gave me 101" for fast descents.

I also built up 13-18T, 13-21T and 13-24T FWs for specific rides but never used them much.

More latterly flexible chains came out about that time too and they helped shifting a lot, even in the small-small, big-big combos. It was a game changer when Shimano brought out their Uniglide chain about 1975.



The bushingless Sedisport chains were just about as good.


verktyg

Chas.

Pemetic2006

Looks like the Cannondale squad was using 28mm tires. I thought 26 would be as "wide" as they'd go at the Tour.

smontanaro 

Yeah, but not for the pave'. I'm sure they were on special purpose bikes which will probably not be used again on the Tour.

Me, I rode to work (slowly) on my Medici with the cushy Challenge Roubaix tubulars (27mm) today. I know a lot of people complain about their construction, but I've had pretty good luck with mine so far.

Bringing this back on-topic, I do find Sheldon's gear calculator handy for fiddling with these half-step calculations. Not only does it give you the gear inches/gain ratios, but it also gives you the percentage jumps between cogs or rings in the column and row headings.



Governor Dodge is going to be tough on that 44x28 combo...

crank_addict

Skip - To heck with half step jiberish on this old stuff. We're riding what should aptly be called 'over the hill' bikes! Looking forward to seeing that Atala. From what you described, should be just fine.

As for myself, I might be in a little deep but here's what I'm going with. And with an ally cottered crank (finally have the correct bb spindle) ify on grinding that hill.


Though due to petri dish carrying g-kids, I'm quite under the weather right now. Been solid for a good 4 - 5 years but of all the timing, jeez! Swimming laps and then grinding 30 miles out on the tall geared 5 speed only Bottecchia is my daily regiment.

Road Fan

Now that I've looked back, yes, I did see it - sorry for forgetting!

I agree with you about the 1.5's! Berto said that if rats can learn to run mazes, cyclists can learn to shift 1/2s (I assume he also meant 1.5's). I can handle 1/2s, but never could adjust to a 1.5 when I made one. I similarly don't really like modern compacts, but on the one compact bike I have I don't want to spring for a triple Ergolever. I may go to triple anyway and just see what happens ...

The secret spreadsheet formula I have is to create a new column that computes the ratio of each adjacent rear gear pair, then use "STDEV()" to compute the standard deviation of that set of numbers. For a 10 speed you should have 9 ratios. The smaller the standard deviation is the closer your cog set is to being an ideal one, from a ˝ step point of view. You can play with the model to see how a single tooth change affects the number. I can't give any real insight on how such a small change affects riding, just that it can be seen to create duplicate gears in a system that is not supposed to have any duplicates. If that's an irritant, so be it. If not, ride happily!

mountaindave 

Whether you're CV or not, that's a good motto to live by.

smontanaro 

bwilli88 

42/39 up front and 11-32 out back 11,13,15,18,21,24,28,32.

portkatterno

I find this half step gearing very interesting and I am tempted to try it for my self. What dérailleurs are you using? They look like ordinary road mechs to me.

fietsbob

6 speed rear of Brompton BWR, Hubs have 2 cogs and 3 internal gears .

My '85 Specialized Expedition had a 48,44,28 crank set , long ago ..

bwilli88 

7 speed Shimano 105 Fd-105* & Rd-105* with Sora 8 speed DT shifters with a Shimano HG-51 8 speed 11-32 cassette. The crank is FC-1050 with Shimano 42t & 39t chainrings. rides real nice.

Barrettscv 

My 1971 Peugeot PX10 has an OE Stronglight 93 crankset. I installed a 46t outer ring, a 42t middle ring with attachment points for a 74 bcd 30t granny gear. The chainrings are now 46, 42 & 30 which will provide a half step and a granny gearing by using the installed 13-15-17-20-23-26 freewheel.

I'm not a masher and like to sit and spin at a 90 to 105 rpm cadence. The Red Clover triplitizer with the 46, 42 and 30 chainrings covers the 12 to 30 mph range with tight gear spacing of 8% or less. It also allows me to use a short cage rear derailleur with a triple. I can hold almost 30 mph on a 46 chainring chainring with a 13 cog on the freewheel. I won't be walking too many hills with that 30t granny gear, either.

An NOS Simplex rear derailleur and a NOS Suntour front derailleur were installed. A Dura ace set of shifters were added along with a very nice Huret cable guide.

Not pictured is a OE PX10 wheelset with Peugeot branded (Mallaird made) hubs and Super Champion sew-up rims. A 14-15-17-19-21 five speed freewheel is mounted. This wheelset will be restored and once new tires are glued on, will be ridden on special days.

Normally, the clincher wheelset will be installed as pictured. These have Campagnolo Record 36 hole high-flange hubs. A 13-26 six speed Suntour freewheel is installed. The Tires are 700 x 32 Compass Stampede Pass. It 's very smooth ride.

portkatterno

I am a bit surprised that a Shimano 105 RD can handle a 32t cog. If I remember correctly factory specifications is maximum 26t but 28t has never been a problem for me. I have several short cage RDs and will try some of them in my own build. Thanks so much for your reply.

bobbyl1966

How i learn what gearing i have on my bikes. What step is. in three bikes i have 53/39 crank and 9 speeds cassete. In one mountain bike i do experiment i have put 52/42 crank and 8 speeds cassette 13/30 and in one road bike i put 50/40 crank and 8 speeds cassette 112-30

mountaindave 

See my above posts - I currently have a tricolor 600 RD running a 11-34 setup without a problem. It doesn't particularly like cross-chaining the highest and lowest gears, but it will handle the 34 tooth without a longer B-screw and I didn't really have to mess with the limit that much anyway. I think the tightly spaced chainrings allows RDs to handle a wider range in the back.

cny-bikeman

Just ride your bikes - different gearing will not make you faster. If you are really interested just Google 1/2 step gearing. There's no point in explaining here info that is readily available.

smontanaro 

The drop of the derailleur hanger has something to say about what will work as well. Most of my bikes have Campy 1010 dropouts of some variety. @crank_addict gave me a 1981 Schwinn Super Sport frame (thanks again Scott - I'm still working on it) that has SunTour GS dropouts. The difference in the hanger drop was significant, something like 17.5mm vs 21mm. I expect that will allow me to run with a SunTour Superbe rear derailleur and a larger-than-max-rated large cog.