ACHiPo 

I finally got the project bike last night and discovered I was off a bit on ratios. The front chainrings are 52/40, and the 5-speed freewheel is 14-30. Will keep my eye out for a SR triple while I refurb the bike. I can likely live with the 40-30 ratio by standing up, although that's not as fun as a Clyde as it used to be when I weighed 145 lbs.

John E

Another endorsement for a triple up front. Here is my mountain bike gearing, which goes a bit below 1:1, with good ratiometric progression:

46-38-28 (or 26, or even 24) / 12-13-15-17-20-23-26-30 1.5-step on the middle and large rings, crossover between the middle and small rings

Cassette was off-the-shelf, with replacement of the stock 11-tooth lockring with my 12-tooth.

ACHiPo 

Unfortunately the selection is limited for vintage drive trains--ie the biggest minimum cog is 13. I see there is an option for "custom", but I don't see where to enter the cog sizes.

abdon 

What?! This is where we Clydes excel at! No twig can compete when we get off the saddle and start pushing down 200+ pounds onto them pedals

Do confirm what is the BCD on that crank of yours. If an old double chances are it is a 130 BCD which means you can buy yourself a tiny amount of wiggle room with a 38t ring. As I mentioned before you don't have to run a triple ring on a triple crank. Old school triple was 110/74 BCD; at 110BCD that buys you all the way down to 33t. If you stick to a 52 big ring it would be a huge ca-klunk to shift but it would shift.

Or get a TA touriste crank and you can have any chainring combo imaginable, including the ones that makes no sense. Heck you could have a quadruple crank for all it cares.

abdon 

I think he wants to stick with a freewheel.

ACHiPo 

I will check the BCD tonight. I might be able to drop down to a 38. Not sure how well the 7GT front derailleur will handle a 14 tooth jump, but then I'm also not sure how well it would handle a triple, especially if I go something 52/40/26.

Regarding the cassette, yes I plan to keep the freewheel, although that 14 tooth cog seems huge compared to what's available on modern cassettes. If I could go to a 10 or 11 tooth, I could drop the big crank rink down to mid-40s which would make things easier on the FD.

ShannonM

You don't enter cog sizes, you slide the little cog symbols back and forth with your mouse. There's no instructions, but if you play with it, you'll get it.

When evaluating gearing with this tool, and it's the best bicycle gearing tool ever made, I usually start with one chainring, so that I can see what the spacing of the rear looks like, (the numbers along the bottom of the graph are % change between cogs,) and what my high gear is going to be. (I prefer 90 - 100 inch gears, and the first thing I'll sacrifice is top end, but that's me.) Then I slide a second chainring over from the left-hand side, and keep an eye on the relationships between the gear arrows on the graph. This is where you can really see, and play with, the tradeoffs between range, spacing, and shift pattern. For triples, I usually just pick the smallest granny ring I think I can get away with with the parts I'm using, but I do put it into the tool for a sanity check.

--Shannon

ACHiPo 

Shannon,
Thanks. That makes sense!
Evan

abdon 

Do you spend a lot of time on the 54/14 combo? That's 101 gear inches, which is adequate for a grocery getter. My touring high setup is 48/11 or 115 gear inches, which gives me a strong cruising speed on flats. A common road bike setup would be 52/11 on 700c or 124 gear inches. I don't have the legs for that.

Gearing is a personal thing and a matter of cadence; some folks sustain higher speeds at higher cadence/lower gearing. I'm a lower cadence kind of guy so 115 gear inches is as high as I go.

abdon 

Also anything lower than say 22 gear inches is worthless. You would walk faster.

RiddleOfSteel

48/11 would be cookin' for me on the flats. Heck, that's a good mild-slope downhill gear. Good times. I spin at 60-80 rpm pretty happily, so like you, a statistically taller set of gears is preferable. 53-11 for me on downhills since I live in the NW. Takes a little more than a 5% grade to aid me in spinning that ratio out (120 rpm or so), otherwise, 80-ish rpm in that gear combo allows me to have a lot of fun on downhills just outside of town here (after spinning a 39-28 up it for a bit...).

ACHiPo 

Top gear is 52/14 and wheels are (will be) 700c, so not quite so high, but not sure how much I'll use it. Could probably drop down to 48/14, but as others have said, when the wind is at your back or you're going down hill, it's kinda fun to keep pedaling. My cadence is generally in the 50s-60s and I am definitely not a racer. I do enjoy cruising on gravel at 15 mph and tarmac at 20-ish, so 52/14-18 should be pretty good for those.

ACHiPo 

...and fall down

abdon 

My friend still laughs remembering the day I tried to pedal up a steeeep wet incline on my granny gear. I hit wet leaves and for a long moment I was pedaling like a crazed mouse on an exercise wheel while the bike was actually going backwards. Falling put a stop to that shenanigan....

52telecaster

When pulling music gear in a trailer up fairly steep inclines I routinely use 26-32 in 700c or a hair below 22". I'm nowhere near falling over. It can be very useful to have low gears. When actually touring I usually have a bailout below 20". When you need one it's a life saver and yes, you are still going faster than if you pushed a loaded tourer up the same hill.

ACHiPo 

I measure the BCD at 118 mm +/- (it's not that easy to precisely and accurately measure a BCD)
.

cyccommute 

Nope. That’s not the right bolt circle diameter. It looks like yours is a 110 but you can measure it by measuring center to center between two adjacent bolts and multiply by 1.70 which will give you the BCD in mm.

cyccommute 

Yes but riding is more efficient. A 22 inch gear is hardly a granny gear. It’s 28/34 with a 700C wheel. My touring bike runs a 20/36 with 700C wheels which is a 15” gear and I use it frequently. It’s also a bit faster than walking at about 4.5mph My bikepacking mountain bike uses a 20/40 with 26” wheels which is a 13” gear. I use it frequently also. Slower…3.5mph…but still better than walking.

No, you don’t fall down. You should be able to ride that slow and even stay in a straight line.

ShannonM

While that's not how BCD usually gets measured, it looks like they got it pretty close. And didn't SR have a 118 BCD crankset for a while? I'm pretty sure I've seen "where can I get chainrings for this?" questions on C&R... the answer seems to be "You can't."

--Shannon

52telecaster

I think that probably is 118 or some other such odd bcd.

abdon 

Either that requires an RPM way up there or your gear inches are not what you think they are. You should do a direct measurement to confirm (measure the bike travel per revolution of the crank).

Off the saddle I can maintain around 70rpm, which at 22 gear inches would have me at 4.5mph and able to tackle a really good incline . On a bigger incline by the time I'm down to 50rpm I'm at walking speed. Your 20/36 would put you at 3mph at the same 70rpm

John E

No problem. The bike came with a 6-speed freewheel, and the previous owner had upgraded to a 7-speed. My 8-speed upgrade to a newer wheelset with a freehub and the same OLD was a relatively recent change.

With a 7-speed freewheel, I was running 48-40-28 / 13-15-17-19-21-24-28, which gave me a perfectly adequate 96 gear inch top instead of my current 100, and a 1:1, 26 gear inch low gear. It worked with a 24-tooth inner chainring, but the 24-to-40 upshift in front had to be done with finesse. 28-to-40 worked much more easily.

cyccommute 

Learn something every day. Sheldon Brown lists a 118mm BCD for SR and Ofmega with a note that it is “obsolete”. Never run across one. It’s still easier and more accurate to measure adjacent ring bolts and multiply by 1.7.

cyccommute 

4 mph at 90 rpm. Not really an RPM that is “way up there”. At 60 rpm, the speed is just under 3 mph which is still rideable and, on a hill, faster then a walking while pushing a bike. With a 22” gear, you have to work harder to pull up the same hill

Sierra

Do you know of a f. der. that could shift across that?
I put one together for giggles but it just hangs above my workbench as a decoration.