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Is There A Reason Why Threaded Freewheels For 120mm Hub Max Out At 34T?

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Is There A Reason Why Threaded Freewheels For 120mm Hub Max Out At 34T?

Old 05-09-21, 05:24 PM
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zandoval 
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Is There A Reason Why Threaded Freewheels For 120mm Hub Max Out At 34T?

Jus Thinken...

Is There A Reason Why Threaded Freewheels For 120mm Hub Max Out At 34T?

I have been real happy with my economical Shimano 6 speed 14-34T touring freewheel and; I actually spend more time on my 34T cog than I would like to admit.
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Old 05-09-21, 05:49 PM
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They don't, or didn't. Suntour made a 38 as did Sachs. Of course it was helicomatic but it was still a thread on.
I'm sure there's specific engineering arguments for why they didn't go bigger but the obvious answer was to add smaller chainrings to expand the range of gearing.

edit...on second thought, the Sachs was likely spaced for 126. I've got one and will check.

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Old 05-09-21, 05:49 PM
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Not much demand and not many RDs that have that sort of capacity. The real problem is that you are talking about huge jumps in your gearing since you can only fit 5 or 6 in 120 OLD. Better to go smaller up front to get the gears you need either with a triple or a "compact" double. That's how I just set up my 70s Motobecane Grand Record, with 50/34 chainrings and a 14-28 freewheel. If I needed better climbing gears, I could have installed smaller chainrings.

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Old 05-09-21, 06:21 PM
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According to Sheldon Brown:
Freewheels screw onto the hub without any tools, then, as you ride the bike, your pedaling effort tightens them down.A freewheel that has been ridden for a long time, especially by a strong rider with low gears, may be quite difficult to remove because the threads are so tight.
Beyond 6-speeds the axle starts becoming an issue, especially with lower gears or in touring conditions. So you risk the axle snapping.

But if it is 120 OLD you are looking for then check out this 120mm cassette hub by SunXCD (Modern Suntour) and build your own 6/7-speed cassette in 14-36 if you want.
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Old 05-09-21, 06:23 PM
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The Sachs SDS-8 was indeed 120 but not a 38 tooth. At least you got 8 cogs...
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Old 05-09-21, 06:30 PM
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Originally Posted by bikemig View Post
Not much demand and not many RDs that have that sort of capacity. The real problem is that you are talking about huge jumps in your gearing since you can only fit 5 or 6 in 120 OLD. Better to go smaller up front to get the gears you need either with a triple or a "compact" double. That's how I just set up my 70s Motobecane Grand Record, with 50/34 chainrings and a 14-28 freewheel. If I needed better climbing gears, I could have installed smaller chainrings.
...yeah, what he said. A lot of my old bikes max out at 24 or 26 in the back. There were other ways to get lower gears back then.
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Old 05-09-21, 06:34 PM
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Originally Posted by zandoval View Post
Jus Thinken...

Is There A Reason Why Threaded Freewheels For 120mm Hub Max Out At 34T?.....
I doubt there is a conclusive answer, but my guess is that there wasn't a demand for it.
With a suitable triple crankset, there's really not a reason to go bigger than 30 or 32T.





Steve in Peoria
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Old 05-10-21, 07:12 AM
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Obviously, cyclists back then were much stronger and tougher than the softies we see today.

Actually, I suspect it is because the >34T sprockets are mainly useful for off-road riding, which didn't become popular until around the same time that freehubs/cassettes also became popular.
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Old 05-10-21, 07:31 AM
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Originally Posted by bikemig View Post
Not much demand and not many RDs that have that sort of capacity. The real problem is that you are talking about huge jumps in your gearing since you can only fit 5 or 6 in 120 OLD. Better to go smaller up front to get the gears you need either with a triple or a "compact" double.
Another factor in the argument for smaller chanrings over larger cogs is weight. Using large cogs increases weight, while smaller chainrings decrease weight. The weight decrease is amplified by the fact that that cogs are typically heavier steel, while chainrings are typically light luminum.
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Old 05-10-21, 07:45 AM
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In the 1960s Chuck Harris offered super wide gearing set-ups in limited quantitites, under his Beech Hill brand. Frank Berto reported that Harris' favourite set-up paired a 13-17-26-34-42T freewheel with 68/44/26T chainrings. In addition to manufacturing the cogs and chainrings, he also manufactured the deralilleurs to handle them.
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Old 05-10-21, 08:39 AM
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Originally Posted by T-Mar View Post
In the 1960s Chuck Harris offered super wide gearing set-ups in limited quantitites, under his Beech Hill brand. Frank Berto reported that Harris' favourite set-up paired a 13-17-26-34-42T freewheel with 68/44/26T chainrings. In addition to manufacturing the cogs and chainrings, he also manufactured the deralilleurs to handle them.
Wow, by chance do you have any photos of those setups?
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Old 05-10-21, 08:47 AM
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For the Back In The Day part of it, I think it was less an issue of lack of demand and more that triple cranksets with small inner chainrings were a far better/easier solution. For all the reasons called out above.

I think the move to those few 38t freewheels was due to the touring boom and the emergence of the ATB market, where a larger number of buyers found a need for gears lower than 24f/34r. And by then the market was moving to 126mm axle spacing.

For the present day part of it, I think it's a combination of lack of enthusiast demand for 120mm freewheels, and low overall production volume. But I know pretty much nothing about modern worldwide low-end bicycle spec.

And for significantly lower gears on a vintage 120mm-axle rig, either a triple w/tiny granny gear or a double with significantly smaller rings is still the easiest/best route to Low Gear Nirvana. And good luck trying to find a front der that's going to allow a small outer ring on a vintage frame with over-bb cable routing. Even under-bb routing can be tough.
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Old 05-10-21, 12:11 PM
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Originally Posted by Mr. 66 View Post
Wow, by chance do you have any photos of those setups?
There's a (poor) illustration of one in The Dancing Chain, if you have a copy. I vaguely recall seeing a photo of one in one of my old cycling a\magazines but it would probably take forever to find.
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Old 05-10-21, 05:58 PM
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Originally Posted by Mr. 66 View Post
Wow, by chance do you have any photos of those setups?
that reminds me of a couple of articles in the Rivendell Reader about Mr. Chuck Harris.
I've got the first one scanned from issue #5 (just scanned it today).
There's another one that I have yet to scan, which gives details about one of his bikes and the drivetrain. Amazing stuff!







Steve in Peoria, where the scanner has been getting a heck of a workout lately!
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Old 05-10-21, 06:24 PM
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5 speed freewheeled bikes were often setup for half step gearing.

14-17-21-26-32 and say a 45/50 up front. That is what I used. I don't recall anything bigger than 32 and if so, it would mess up the half step pattern.
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Old 05-10-21, 06:30 PM
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I have a 14-17-21-26-32-38 Suntour Perfect on my Miyata 1000, with a 28-42-46 in front. It's a good half-step setup. I don't use the 28-38 very often, but I find it comforting to have it available.

Suntour Perfects are cheap, plentiful, and easy to customize. The 38 cogs aren't exactly plentiful, but they're not hen's teeth, either.
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Old 05-10-21, 06:49 PM
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My "Beast of the East" Suntour ProCompe Ultra spaced 6 speed in my 120mm spaced 1971 Schwinn Paramount P13.




IIRC, 17-20-25-30-34-38 coupled to 50-42-31.

The Suntour 38T will fit on Perfect, ProCompe, Winner, New Winner, and Winner Pro and I believe Alpha bodies. They are not easy to find, but keep checking ebay.
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Old 05-10-21, 07:13 PM
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Originally Posted by pastorbobnlnh View Post
My "Beast of the East" Suntour ProCompe Ultra spaced 6 speed in my 120mm spaced 1971 Schwinn Paramount P13.
..........
IIRC, 17-20-25-30-34-38 coupled to 50-42-31.

The Suntour 38T will fit on Perfect, ProCompe, Winner, New Winner, and Winner Pro and I believe Alpha bodies. They are not easy to find, but keep checking ebay.
I'm scratching my head trying to figure out why SunTour made a 38T cog when none of their derailleurs (to my knowledge) could handle it.
A mystery for the ages!

... or did the Duopar-ish Mountech handle cogs of that size?....



I'm also trying to figure out why I have this derailleur, but no plans to ever use it.

Steve in Peoria
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Old 05-10-21, 07:16 PM
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Originally Posted by steelbikeguy View Post
I'm scratching my head trying to figure out why SunTour made a 38T cog when none of their derailleurs (to my knowledge) could handle it.
A mystery for the ages!

... or did the Duopar-ish Mountech handle cogs of that size?....



I'm also trying to figure out why I have this derailleur, but no plans to ever use it.

Steve in Peoria
You just need to find that 38 tooth suntour cog to try out that derailleur for TOMRV!
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Old 05-10-21, 07:26 PM
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Originally Posted by bikemig View Post
You just need to find that 38 tooth suntour cog to try out that derailleur for TOMRV!
maybe if I was running a 42-52 crankset.

I've been riding my Borthwick for TOMRV lately, configured with one of those fancy modern 8 speed cassettes. I think it is 11-28 right now, and with the 34-50 compact crank, it handles the hills of TOMRV well enough.



I'm pretty sure I used to ride the Borthwick with a 39 x 26 low gear, but that was probably 30 years ago. The hills were smaller then.

Steve in Peoria
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Old 05-10-21, 07:38 PM
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Originally Posted by steelbikeguy View Post
I doubt there is a conclusive answer, but my guess is that there wasn't a demand for it.
With a suitable triple crankset, there's really not a reason to go bigger than 30 or 32T.


Steve in Peoria
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Old 05-10-21, 07:53 PM
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Originally Posted by steelbikeguy View Post
maybe if I was running a 42-52 crankset.

I've been riding my Borthwick for TOMRV lately, configured with one of those fancy modern 8 speed cassettes. I think it is 11-28 right now, and with the 34-50 compact crank, it handles the hills of TOMRV well enough.



I'm pretty sure I used to ride the Borthwick with a 39 x 26 low gear, but that was probably 30 years ago. The hills were smaller then.

Steve in Peoria
The hills were smaller BITD. Yeah I don’t run 144 bcd cranks anymore. I wouldn’t want to run a 38 on the back as the jumps become too large for my liking unless you customize a freewheel like pastorbobnlnh did. A 34 running on a 28 is a nice low gear.
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Old 05-10-21, 08:01 PM
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Originally Posted by steelbikeguy View Post
I'm scratching my head trying to figure out why SunTour made a 38T cog when none of their derailleurs (to my knowledge) could handle it.
A mystery for the ages!

... or did the Duopar-ish Mountech handle cogs of that size?....



I'm also trying to figure out why I have this derailleur, but no plans to ever use it.

Steve in Peoria
Suntour AG

Last edited by clubman; 05-10-21 at 08:06 PM.
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Old 05-10-21, 08:13 PM
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Originally Posted by clubman View Post
Suntour AG

SunTour AG Tech derailleur (5000)

this has a discussion of the AG rear derailleur and Suntour’s 14-38 5 speed freewheel
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Old 05-10-21, 09:00 PM
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Originally Posted by Mr. 66 View Post
Wow, by chance do you have any photos of those setups?
okay... here's the article that shows the majesty and uniqueness of Chuck's creations! Just amazing!







Steve in Peoria
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