Beyond MegaRange: Extending 7-speed Cassette Range?
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Beyond MegaRange: Extending 7-speed Cassette Range?
I'm wondering if the range of a Shimano Tourney 14t-34t cassette/freewheel -- with a single chainring -- can be expanded.
Are there bigger cogs than 34t (and derailleurs that can shift to them)?
Sheldon Brown describes something complicated about special hubs being needed for 11t cogs. Does that apply also to 12t and 13t?
I notice that Shimano's own 7-speed 11-34 cassette and freewheel were discontinued. Is there something inherently problematic about this configuration?
Are there bigger cogs than 34t (and derailleurs that can shift to them)?
Sheldon Brown describes something complicated about special hubs being needed for 11t cogs. Does that apply also to 12t and 13t?
I notice that Shimano's own 7-speed 11-34 cassette and freewheel were discontinued. Is there something inherently problematic about this configuration?
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In general, anything that starts with a 14-tooth cog is probably a thread-on freewheel not a cassette. Sheldon explains the difference, but you seem a little uncertain what you have, so I'd recommend reading this. Freewheels with sub-14-tooth top cogs are pretty unusual, and the ones that exist don't index with Shimano shifters as far as I'm aware, so in your case, a "special hub" would be the only way to get a smaller cog, because you'd need a cassette freehub rather than a hub that takes a thread-on freewheel.
With a cassette, you can customise the gearing by drilling out the rivets holding the sprockets together and then replacing individual sprockets as you see fit, but replacement sprockets for old-fashioned freewheels aren't really available anymore. Also, almost all modern cassette freehubs are designed for an 11-tooth small rear sprocket, so Sheldon's information regarding what works with current cassette hubs is a little out-of-date.
With a cassette, you can customise the gearing by drilling out the rivets holding the sprockets together and then replacing individual sprockets as you see fit, but replacement sprockets for old-fashioned freewheels aren't really available anymore. Also, almost all modern cassette freehubs are designed for an 11-tooth small rear sprocket, so Sheldon's information regarding what works with current cassette hubs is a little out-of-date.
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The SRAM XXI system has a 10-42T 11 speed cassette with a single chainring.
It is designed for mountain bike use: for frames that can't use a front derailleur or for riders who have problem with dropping the chain from the chainrings of a double or triple crank. I haven't encountered either situation.
The downside is big gaps between gears.
Without using the SRAM components or modifying some other components, I don't think going larger than 34T will work, as you are limited by available rear derailleurs.
On the road, I think a rider who needs a very low gear (>34T) probably does not need a very high gear (a 11T), as he is not strong enough to use it, except on a downhill which is pointless, better to spin a high cadence or simply get in a tuck.
It is designed for mountain bike use: for frames that can't use a front derailleur or for riders who have problem with dropping the chain from the chainrings of a double or triple crank. I haven't encountered either situation.
The downside is big gaps between gears.
Without using the SRAM components or modifying some other components, I don't think going larger than 34T will work, as you are limited by available rear derailleurs.
On the road, I think a rider who needs a very low gear (>34T) probably does not need a very high gear (a 11T), as he is not strong enough to use it, except on a downhill which is pointless, better to spin a high cadence or simply get in a tuck.
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I thought 34 was normally the bigges cog and needed shipmanos "Mega Range" RD? I think a 34x34 sounds pretty low already. You might be better off dropping to a 32 or 30T in the front. Depending on your crank you could mount a second ring like a 28T and just change by hand like in the old days.
OH just doing some research I guess Mega Range refers to the ridiculous spread from a 11 to a 34 cogset. But I still say a 34 is pretty big in the back.
OH just doing some research I guess Mega Range refers to the ridiculous spread from a 11 to a 34 cogset. But I still say a 34 is pretty big in the back.
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At some point it might be less hassle to just go with a double up front, unless you have some moral or aesthetic objection. Covering this type of extreme range is why the use of multiple front chainrings was developed.
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I thought 34 was normally the bigges cog and needed shipmanos "Mega Range" RD? I think a 34x34 sounds pretty low already. You might be better off dropping to a 32 or 30T in the front. Depending on your crank you could mount a second ring like a 28T and just change by hand like in the old days.
OH just doing some research I guess Mega Range refers to the ridiculous spread from a 11 to a 34 cogset. But I still say a 34 is pretty big in the back.
OH just doing some research I guess Mega Range refers to the ridiculous spread from a 11 to a 34 cogset. But I still say a 34 is pretty big in the back.
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Very true. It just isn't that hilly around here, nor where I used to live near Boston so I never got used to super low gearing like that.
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IIRC Sun Tour (?) once offered a 14x38 freewheel. The problem with huge range freewheels and cassettes is that they have big gaps between adjacent gears and even 10 and 11-speed cassettes can't compensate. The simplicity of a single chainring gets compromised by lack of intermediate gears. You can't have it both ways
My first "good" bike was a 1985 Bridgestone 400 with a 14x32 6-speed Sun Tour freewheel and a 52/42 SR double crank. The freewheel was 14,16,20,24,28,32. Note the huge gap between the 16 and 20T cogs. I redid the crank as a half-step (46/42) to fill in those gaps but lost too much on top. .
My first "good" bike was a 1985 Bridgestone 400 with a 14x32 6-speed Sun Tour freewheel and a 52/42 SR double crank. The freewheel was 14,16,20,24,28,32. Note the huge gap between the 16 and 20T cogs. I redid the crank as a half-step (46/42) to fill in those gaps but lost too much on top. .
Last edited by HillRider; 02-15-13 at 09:46 AM.
#10
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Some of the newer 9 or 10? speed cassettes are now coming out with a 36T cog, but that's not much of a gain over 34.
A smaller chain ring is the way to get lower gearing.
A smaller chain ring is the way to get lower gearing.
#11
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Rebuild the wheel around a Sturmey or Sram Hybrid ,dual drive; 3 internal, cassette external gear, combination hub.
then the 34t is .75 lower.. the high, 1.333 higher.
current cassette driver type is 8~9 speed, 7 is a prior Sachs product, before Sram buyout. {ebay for used ones)
then the 34t is .75 lower.. the high, 1.333 higher.
current cassette driver type is 8~9 speed, 7 is a prior Sachs product, before Sram buyout. {ebay for used ones)
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https://www.abundantadventures.com/quads.html
https://www.abundantadventures.com/mt...g-removal.html
#14
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hmm? 13T was the defacto standard high gear on better bikes in the freewheel days. 13-21, 13-24, and 13-26 were common 5 speed freewheels but you could build up most anything you wanted. the summer I lived in the flatlands, I ran a 13-17 'straight block'.
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OK so looks like customizing freewheels is impossible today (without antique parts).
Looks like customizing a 7-speed cassette for 11t-34t would be possible -- if a lot of work and expense just to replicate the Shimano 11-34 MegaRange freewheels and cassettes that were available a few years ago:
https://harriscyclery.net/product/shi...et-cog-801.htm
https://harriscyclery.net/product/shi...rocket-800.htm
spacers and such uncertain
No possibility to go beyond 34t on any 7-speed system ever due both to lack of bigger gears and derailleurs.
Looks like customizing a 7-speed cassette for 11t-34t would be possible -- if a lot of work and expense just to replicate the Shimano 11-34 MegaRange freewheels and cassettes that were available a few years ago:
https://harriscyclery.net/product/shi...et-cog-801.htm
https://harriscyclery.net/product/shi...rocket-800.htm
spacers and such uncertain
No possibility to go beyond 34t on any 7-speed system ever due both to lack of bigger gears and derailleurs.
#16
S'Cruzer
most newer 7 speed systems can be converted to 8 speed with just a different shifter and the 8 speed cassette. that gives you a much bigger choice of cassettes.
but, SRAM has a 12-32 7 speed, thats a pretty wide range. difference between a 32 and 34 is only a few percent.
there's a shimano 13-34, which I'd RATHER have than 11-34.
but, SRAM has a 12-32 7 speed, thats a pretty wide range. difference between a 32 and 34 is only a few percent.
there's a shimano 13-34, which I'd RATHER have than 11-34.
#17
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In general, anything that starts with a 14-tooth cog is probably a thread-on freewheel not a cassette. Sheldon explains the difference, but you seem a little uncertain what you have, so I'd recommend reading this. Freewheels with sub-14-tooth top cogs are pretty unusual, and the ones that exist don't index with Shimano shifters as far as I'm aware, so in your case, a "special hub" would be the only way to get a smaller cog, because you'd need a cassette freehub rather than a hub that takes a thread-on freewheel.
With a cassette, you can customise the gearing by drilling out the rivets holding the sprockets together and then replacing individual sprockets as you see fit, but replacement sprockets for old-fashioned freewheels aren't really available anymore. Also, almost all modern cassette freehubs are designed for an 11-tooth small rear sprocket, so Sheldon's information regarding what works with current cassette hubs is a little out-of-date.
With a cassette, you can customise the gearing by drilling out the rivets holding the sprockets together and then replacing individual sprockets as you see fit, but replacement sprockets for old-fashioned freewheels aren't really available anymore. Also, almost all modern cassette freehubs are designed for an 11-tooth small rear sprocket, so Sheldon's information regarding what works with current cassette hubs is a little out-of-date.
#18
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More generally, I've seen some ancient SunTour rear sprockets that are 38 teeth. It would take some surgical procedures to put one on an existing cassette or freewheel, but it gets you past 34. What rear derailleur/dropout combination can accommodate that, I don't know. You might find yourself getting into a gearing/derailleur combination that is unique, ancient, and very difficult to find a full group in good condition, and that might not even deliver what you expect on some frames.
If you need more range past the currently available 11/32 10-speed system which can be purchased off the shelf, I think you need to address the chainrings as well as the rear end. If you need to stick with the 7-speed spin-on freewheel, you can find a 13-34 Megarange, or if you hunt a 13-32 Sachs-Maillard 7-speed freewheel. SunTour also made some similar wide-range combinations. The Sachs and Suntour units usually had an even gear spread across the range, not the roadie-spread-plus-deep-bailout that the Megarange represents.
If you need more range past the currently available 11/32 10-speed system which can be purchased off the shelf, I think you need to address the chainrings as well as the rear end. If you need to stick with the 7-speed spin-on freewheel, you can find a 13-34 Megarange, or if you hunt a 13-32 Sachs-Maillard 7-speed freewheel. SunTour also made some similar wide-range combinations. The Sachs and Suntour units usually had an even gear spread across the range, not the roadie-spread-plus-deep-bailout that the Megarange represents.
#19
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Maybe if you said "some" , which would be the ones with the 8 speed body + 4.5mm spacer.
I would also think "most" 7 speed "systems" are a free wheel which means you'd have to change the hub.
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The key word is "were". I don't think they make them anymore, and if they do, I doubt the pricing will be anything like that of a Tourney freewheel.
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So how do you fit the longer 8 speed cassette on the shorter 7 speed free hub body?
Maybe if you said "some" , which would be the ones with the 8 speed body + 4.5mm spacer.
I would also think "most" 7 speed "systems" are a free wheel which means you'd have to change the hub.
Maybe if you said "some" , which would be the ones with the 8 speed body + 4.5mm spacer.
I would also think "most" 7 speed "systems" are a free wheel which means you'd have to change the hub.
#22
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I'm wondering if the range of a Shimano Tourney 14t-34t cassette/freewheel -- with a single chainring -- can be expanded. Are there bigger cogs than 34t (and derailleurs that can shift to them)? Sheldon Brown describes something complicated about special hubs being needed for 11t cogs. Does that apply also to 12t and 13t? I notice that Shimano's own 7-speed 11-34 cassette and freewheel were discontinued. Is there something inherently problematic about this configuration?
#23
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Look Here: https://www.abundantadventures.com/quads.html
The parts are drying up fast (most show sold out status) but looks like one can still buy enough items from them to assemble an 18T granny 4th gear...for something like a 50-40-30-18T quad for not much cash.
The crank has to have a 74mm BCD for the inside 3rd ring mounting or the adapter won't fit. How to shift it is not clear on the website; I've ask and will post any answers.
I'll likely then buy a set to keep for some future venture...who knows when a 18T chainring and a 36T cog might come in handy or at least amusing. Total cost of the adapter and 18T ring from them is $33. Haven't heard back yet if different/longer bolts are required (likely).
Hope that helps close on the thought
/K
PS; If need a granny...seems Raceface 22T or 24T granny rings for 74BCD third position are on sale. Found them on Amazon for $14.95. Seems like a bargain.
Last edited by ksisler; 02-20-13 at 09:24 AM.
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Originally Posted by john0
Problematic mechanically I mean -- not in terms of gear spacing preferences.
I'm not sure why Shimano discontinued the 11-xx MegaRange freewheels. Unless you can find one NOS, you'll need to decide where you want to compromise on your gear range to maintain a 1x7 setup -- top or bottom?
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#25
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Unfortunately I don't see that you included your chainwheel size, but why can't you simply reduce the number of teeth in front? A 44/11 still gives you a 108 inch gear, which is enough to pedal well into 30mph+.