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Changing gear ratios

Old 04-24-24, 12:26 AM
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Originally Posted by Bill Kapaun
Don't care.
..
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Old 04-24-24, 05:02 PM
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Originally Posted by Duragrouch
I dunno about that. If, theoretically, you have a big enough difference in chainrings so that there is no overlap, then you start on the small ring, go through the entire cassette, switch to the big ring, then go through the entire cassette. Sequential. Bromptons are like this, no overlap. Low range on the IGH, 1,2 on the cogs. Medium range, 1,2 on the cogs. High range, 1,2 on the cogs. Zero overlap. And, the spacing between 1,2 on the cogs, is the same as the jump to the next range. So 6 equally spaced gears. I prefer no IGH, but darnit, they really did think out the gearing well. But they also have a special "Brompton Wide Range" IGH, not a standard Sturmey Archer 3.
People did stuff like this 40 years ago. And stopped. Bikes are semi trucks - you don't start in 1 and work your way up to 21. The reason this kind of gearing sucks is that we normally ride in the middle gears, which would make this a huge double shift all the time.

Alpine gearing where you switch back and forth big/small/big/small was also abandoned 40 years ago.

And then there is cross overs, which also suck.
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Old 04-24-24, 05:31 PM
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Originally Posted by Kontact
People did stuff like this 40 years ago. And stopped. Bikes are semi trucks - you don't start in 1 and work your way up to 21. The reason this kind of gearing sucks is that we normally ride in the middle gears, which would make this a huge double shift all the time.

Alpine gearing where you switch back and forth big/small/big/small was also abandoned 40 years ago.

And then there is cross overs, which also suck.
Middle gears... yeah that make sense. I just feel like I still have too much overlap. On my old race bike, 52/42x7, I think 6 gears were dupes. On my current 50/34x7, 5 gears are dupes. I'd like a bit wider crank range to get a bit more than 400% total, without needing bigger steps at the cassette.

When I upgraded my road bike to a triple when I moved to hilly country, I didn't have an even spaced triple. I was working on the road and passing the time outside of work, buying, fixing, then selling bikes. One had a triple, which I swapped with my 52/42 biopace and then sold that bike. The triple was half-step-plus-granny, I don't recall the numbers, and yes, a true middle ring might have been better, I could swap that out easy if I ever ride that bike again. However I don't recall any problems riding it, in fact that middle ring (I'm guessing 46 or 47?) was very versatile, used 98% of time (so proves your argument), I was just super glad for that bailout-low given that my low cog was I think 24 or 25, so that was a huge difference in big hills. I was always spinning back then, hadn't learned to climb out of the saddle like now.

I had to look up up cross-over gearing, and also read the descriptions of all other strategies. I'll have to digest.

My current bike (folder with huge diameter seat tube) won't do a triple on a standard hollow spindle, FD wouldn't go in far enough, I'd need to go back to square taper and get a wide-spindle BB cartridge. I love the hollow spindle system, so I'm hoping in future years for greater than 16T jump, but my guess is development on 2Xs has halted in favor of 1Xs. With lift pins on the outer ring, I would bet I could do a 20T jump, but I would need a 74mm BCD on the inner, I can't go smaller than 34T on 110 BCD.
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Old 04-24-24, 08:10 PM
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Originally Posted by Duragrouch
Yep. In flat land, I rode my road race bike with 52/42 for well over a decade. Moved to a place with hills, it wasn't long until I traded that out for a triple. But that was before wide doubles.
Wide doubles have been around since at least the 1970s, they just weren't mainstream.
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Old 04-24-24, 08:32 PM
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Originally Posted by grumpus
Wide doubles have been around since at least the 1970s, they just weren't mainstream.
Huh, good to know. I think that was before lift pins on the large chainring, right? So how big a jump would upshift OK? I'm thinking that lift pins (or formed protrusions in thin steel rings) help a lot for big up-jumps, but I don't know for sure.
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Old 04-24-24, 08:39 PM
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The early 80’s SR Apex 86bcd crank on the Raleigh Gran Tour currently carries a set of 48/28 chainrings (no pins, flat rings) and shifts like buttah. Mated to an 8 speed 12-34 cassette, friction shifted, it gets me pretty much anywhere. Well, at least anywhere my 72 year old legs can take me with a 28/34 low gear…somewhere in the low 20’s gear-inch-wise.
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Old 04-24-24, 08:41 PM
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Originally Posted by rccardr
The early 80’s SR Apex 86bcd crank on the Raleigh Gran Tour currently carries a set of 48/28 chainrings (no pins, flat rings) and shifts like buttah. Mated to an 8 speed 12-34 cassette, friction shifted, it gets me pretty much anywhere. Well, at least anywhere my 72 year old legs can take me with a 28/34 low gear…somewhere in the low 20’s gear-inch-wise.
What front derailleur makes that work?
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Old 04-24-24, 08:58 PM
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Currently a Shimano CX-70, (the Do Everything FD) but have also sucessfully used a Dura Ace 7400.
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Old 04-24-24, 09:00 PM
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Originally Posted by rccardr
The early 80’s SR Apex 86bcd crank on the Raleigh Gran Tour currently carries a set of 48/28 chainrings (no pins, flat rings) and shifts like buttah. Mated to an 8 speed 12-34 cassette, friction shifted, it gets me pretty much anywhere. Well, at least anywhere my 72 year old legs can take me with a 28/34 low gear…somewhere in the low 20’s gear-inch-wise.
I like that, I ran the numbers, fewer duplicate gears in the middle, great gear range 500% without big jumps at the cogs. That's good news for me. If I need a higher high from my current 85 gear inch (on 20"/406 wheels), I could go 54/34 if I can find a 54 ring on 5x110mm, or if I need a lower low from my current 21 gear inch for loaded touring, I could go 50/30 (would need a new crank on 110/74).

Last edited by Duragrouch; 04-24-24 at 09:12 PM.
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Old 04-24-24, 10:59 PM
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Originally Posted by rccardr
Currently a Shimano CX-70, (the Do Everything FD) but have also sucessfully used a Dura Ace 7400.
Suntour Cyclone FD’s are also a good swiss army knife choice.

John
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Old 04-25-24, 06:27 AM
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Originally Posted by 70sSanO
Suntour Cyclone FD’s are also a good swiss army knife choice.

John
Yep, also a Shimano 6207, which shifted a 48/34/24 triple reasonably well at Eroica CA.
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Old 04-25-24, 12:09 PM
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Originally Posted by Duragrouch
Huh, good to know. I think that was before lift pins on the large chainring, right? So how big a jump would upshift OK? I'm thinking that lift pins (or formed protrusions in thin steel rings) help a lot for big up-jumps, but I don't know for sure.
Stronglight 49D with 32-52 and 14-28 5s on the back. The rings were completely flat and with full profile teeth, as befits a crankset introduced in 1949 (the steel 49A was ten years older but otherwise the same). Campy Record/Rally derailleurs. Wasn't the smoothest upshift but was never a problem as long as you weren't late. The FD broke at the clamp after 11 or 12 years, the RD had already been replaced with IIRC Suntour ARX GT when its cage spring broke.
At some point before the FD broke I'd switched to a Stronglight 99 with 32-44 and 13-32 7s on the back, I don't recall what the replacement FD was.
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Old 04-26-24, 04:42 PM
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I had 23 tooth cassette on my 91 pgd Paramount. I put on 28 tooth and the old 105 short cage shifted it fine. I later went to a 32 tooth cassette and it would not clear the big gear. I went on line and found a short cage that is rated to 34 teeth. It works very smooth shifting into the big gear. I put the old short cage 105 on another 8 speed 28 tooth cassette bike and it is smooth shifting. Both bikes are 52-39 chainrings. I did replace chain.
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Old 04-28-24, 02:33 AM
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Originally Posted by grumpus
Stronglight 49D with 32-52 and 14-28 5s on the back. The rings were completely flat and with full profile teeth, as befits a crankset introduced in 1949 (the steel 49A was ten years older but otherwise the same). Campy Record/Rally derailleurs. Wasn't the smoothest upshift but was never a problem as long as you weren't late. The FD broke at the clamp after 11 or 12 years, the RD had already been replaced with IIRC Suntour ARX GT when its cage spring broke.
At some point before the FD broke I'd switched to a Stronglight 99 with 32-44 and 13-32 7s on the back, I don't recall what the replacement FD was.
I've gone almost that far:
.
Stronglight 49D with 52-36
SunTour Ultra 6 13-32
SunTour Cyclone front and back
126 OLD
.
I think that actually gives me slightly more range:
https://www.gear-calculator.com/?GR=...22,28&UF2=2125

Running new TA chainrings and I think 26 is the smallest available (£28.99 new) but reading around suggested that a front jump of 16 was the largest reasonable amount.
Good to know I could try 32 at some point.
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Old 04-30-24, 07:29 PM
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I'm looking for a Shimano 9-speed cassette with the largest cog in the 42T range. The only ones I can find are from the CUES groupset. Since this is for a tandem, the "E-Bike rated" design seems like a good idea. Does anyone know if these are interchangeable with my current Deore XT setup?
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Old 04-30-24, 11:22 PM
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Originally Posted by PromptCritical
I'm looking for a Shimano 9-speed cassette with the largest cog in the 42T range. The only ones I can find are from the CUES groupset. Since this is for a tandem, the "E-Bike rated" design seems like a good idea. Does anyone know if these are interchangeable with my current Deore XT setup?
First, if the ebike has a hub motor, the gears don't get stressed more. Mid-drive, yes. But I would only respect "e-bike rated" if there were numbers to back up that claim. Since cog dimensions are required to be the same, that means either better steel or better surface treatment or both, and test data to back up claims. Otherwise, it's just hype. (Not to be confused with Hyperspaceglide which actually works. Those were the days, significant improvements every year or two, constant trickle-down to the lower groupsets.)

Last edited by Duragrouch; 04-30-24 at 11:27 PM.
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