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#11
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interchangeable hubs?
On Wed, 16 Apr 2008 18:22:36 -0500, Gary Young wrote:
On Wed, 16 Apr 2008 12:47:38 +0000, _ wrote: On Tue, 15 Apr 2008 22:22:36 -0500, Gary Young wrote: On Wed, 16 Apr 2008 02:30:10 +0000, Ryan Cousineau wrote: In article , landotter wrote: On Apr 15, 6:01 pm, Jeff Welch wrote: I have an old huffy 3-speed, my best guess is that it is from the 1970's. I'm just learning how to maintain and repair my own bike, and was wondering if it is possible to convert the current Shimano 3-speed hub to one of their new Nexus 7-speed hubs. Where would I start to figure out if it's even possible? (Tire size, frame fork, something else?) Sure, it's possible. A Sturmey Archer hub might be a better choice for that frame spacing, if you don't want to spread it. Plenty of options with and without brakes. To elaborate, you'll almost certainly want to build a new wheel around the Nexus hub, so just find out what the old wheel size was (you can easily determine that from the tire markings or by taking it to a half-competent LBS), and spec the necessary rim from there. The Nexus 7 hubs can be built with rim, roller, or coaster brake setups, so you can preserve the present braking setup or change it as you prefer. As Landotter suggests, an S-A 7-speed will fit in your frame without changing the rear spacing, though potentially at the cost of a bit of efficiency and niceness that the Nexus hubs have. Does Sturmey make a 7-speed hub? If you mean the 8-speed hub, that may not be a good choice for the OP because the gearing is better suited to small-wheeled bikes: Nonsense. The only difference between a small-wheeled version and a large-wheeled version of a successful Nexus conversion are the sizes of the chainring and rear cog; the internal arrangements of the gearhub have no increased suitablilty for wheels of any size. The only considerations of this order that would be of importance are range of gearing available and maximum torque allowed. Take a look at Sheldon Brown's internal gear calculator: http://sheldonbrown.com/gears/internal.html If the OP has 26-inch wheels, a 170mm crank, and a 40-tooth chainring, then adding the Sturmey-Archer 8-speed hub with its stock 25-tooth sprocket would give him a range of 41.6 to 126.9 gear inches. That strikes me as pretty high for a typical gearhub bike. Now try the Shimano Nexus 8-speed hub with its stock 19-tooth sprocket (all else held equal) and you get a range of 28.8 to 88.4 gear inches. It's true that you could get the Sturmey-Archer down into the Nexus territory with a 28-tooth chainring, but it's my understanding that such a small ring would probably result in rapid wear of the ring and chain (though perhaps I'm mistaken about that). Moreover, the OP, who has an old 3-speed, probably doesn't have a crank with replaceable rings and thus would have to buy a new crank and maybe a new bottom bracket. This problem would be exacerbated if the OP's wheels are larger than 26 inches. So, I don't think it's nonsense to say that the Sturmey-Archer hub is better suited to small-wheeled bicycles (and actually I was just echoing Sheldon Brown's judgment on that). But it is not the HUB that is unsuited to small wheels, it's the rest of the kit. (And chain wear is not made worse by small sprockets until you get into the 11-12-13 tooth range; though 11's have been used on SA multi-gear hubs, and I run a 13 on the Nexus.) |
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#12
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interchangeable hubs?
On Thu, 17 Apr 2008 00:30:20 +0000, _ wrote:
On Wed, 16 Apr 2008 18:22:36 -0500, Gary Young wrote: On Wed, 16 Apr 2008 12:47:38 +0000, _ wrote: On Tue, 15 Apr 2008 22:22:36 -0500, Gary Young wrote: On Wed, 16 Apr 2008 02:30:10 +0000, Ryan Cousineau wrote: In article , landotter wrote: On Apr 15, 6:01 pm, Jeff Welch wrote: I have an old huffy 3-speed, my best guess is that it is from the 1970's. I'm just learning how to maintain and repair my own bike, and was wondering if it is possible to convert the current Shimano 3-speed hub to one of their new Nexus 7-speed hubs. Where would I start to figure out if it's even possible? (Tire size, frame fork, something else?) Sure, it's possible. A Sturmey Archer hub might be a better choice for that frame spacing, if you don't want to spread it. Plenty of options with and without brakes. To elaborate, you'll almost certainly want to build a new wheel around the Nexus hub, so just find out what the old wheel size was (you can easily determine that from the tire markings or by taking it to a half-competent LBS), and spec the necessary rim from there. The Nexus 7 hubs can be built with rim, roller, or coaster brake setups, so you can preserve the present braking setup or change it as you prefer. As Landotter suggests, an S-A 7-speed will fit in your frame without changing the rear spacing, though potentially at the cost of a bit of efficiency and niceness that the Nexus hubs have. Does Sturmey make a 7-speed hub? If you mean the 8-speed hub, that may not be a good choice for the OP because the gearing is better suited to small-wheeled bikes: Nonsense. The only difference between a small-wheeled version and a large-wheeled version of a successful Nexus conversion are the sizes of the chainring and rear cog; the internal arrangements of the gearhub have no increased suitablilty for wheels of any size. The only considerations of this order that would be of importance are range of gearing available and maximum torque allowed. Take a look at Sheldon Brown's internal gear calculator: http://sheldonbrown.com/gears/internal.html If the OP has 26-inch wheels, a 170mm crank, and a 40-tooth chainring, then adding the Sturmey-Archer 8-speed hub with its stock 25-tooth sprocket would give him a range of 41.6 to 126.9 gear inches. That strikes me as pretty high for a typical gearhub bike. Now try the Shimano Nexus 8-speed hub with its stock 19-tooth sprocket (all else held equal) and you get a range of 28.8 to 88.4 gear inches. It's true that you could get the Sturmey-Archer down into the Nexus territory with a 28-tooth chainring, but it's my understanding that such a small ring would probably result in rapid wear of the ring and chain (though perhaps I'm mistaken about that). Moreover, the OP, who has an old 3-speed, probably doesn't have a crank with replaceable rings and thus would have to buy a new crank and maybe a new bottom bracket. This problem would be exacerbated if the OP's wheels are larger than 26 inches. So, I don't think it's nonsense to say that the Sturmey-Archer hub is better suited to small-wheeled bicycles (and actually I was just echoing Sheldon Brown's judgment on that). But it is not the HUB that is unsuited to small wheels, it's the rest of the kit. The OP wants to revamp an old Huffy. I suspect that means he's either not willing or financially able to swap out his entire kit. Besides, at that point he would probably be better off buying a new bike. (And chain wear is not made worse by small sprockets until you get into the 11-12-13 tooth range; though 11's have been used on SA multi-gear hubs, and I run a 13 on the Nexus.) The issue is the size of the chainring, not the sprocket. You don't think a 28-tooth chainring would wear more quickly than a 40-tooth chainring? 28 teeth is getting into granny-gear territory. It was my understanding that granny gears are typically made of steel and not aluminum precisely because they're more prone to wear. Here's an old posting from Jobst that I believe bears that out: http://groups.google.com/group/rec.b...146c8f64ca1dc3 |
#13
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interchangeable hubs?
In article ,
_ wrote: On Wed, 16 Apr 2008 18:22:36 -0500, Gary Young wrote: On Wed, 16 Apr 2008 12:47:38 +0000, _ wrote: On Tue, 15 Apr 2008 22:22:36 -0500, Gary Young wrote: On Wed, 16 Apr 2008 02:30:10 +0000, Ryan Cousineau wrote: In article , landotter wrote: On Apr 15, 6:01 pm, Jeff Welch wrote: I have an old huffy 3-speed, my best guess is that it is from the 1970's. I'm just learning how to maintain and repair my own bike, and was wondering if it is possible to convert the current Shimano 3-speed hub to one of their new Nexus 7-speed hubs. Where would I start to figure out if it's even possible? (Tire size, frame fork, something else?) Sure, it's possible. A Sturmey Archer hub might be a better choice for that frame spacing, if you don't want to spread it. Plenty of options with and without brakes. To elaborate, you'll almost certainly want to build a new wheel around the Nexus hub, so just find out what the old wheel size was (you can easily determine that from the tire markings or by taking it to a half-competent LBS), and spec the necessary rim from there. The Nexus 7 hubs can be built with rim, roller, or coaster brake setups, so you can preserve the present braking setup or change it as you prefer. As Landotter suggests, an S-A 7-speed will fit in your frame without changing the rear spacing, though potentially at the cost of a bit of efficiency and niceness that the Nexus hubs have. Does Sturmey make a 7-speed hub? If you mean the 8-speed hub, that may not be a good choice for the OP because the gearing is better suited to small-wheeled bikes: Nonsense. The only difference between a small-wheeled version and a large-wheeled version of a successful Nexus conversion are the sizes of the chainring and rear cog; the internal arrangements of the gearhub have no increased suitablilty for wheels of any size. The only considerations of this order that would be of importance are range of gearing available and maximum torque allowed. Take a look at Sheldon Brown's internal gear calculator: http://sheldonbrown.com/gears/internal.html If the OP has 26-inch wheels, a 170mm crank, and a 40-tooth chainring, then adding the Sturmey-Archer 8-speed hub with its stock 25-tooth sprocket would give him a range of 41.6 to 126.9 gear inches. That strikes me as pretty high for a typical gearhub bike. Now try the Shimano Nexus 8-speed hub with its stock 19-tooth sprocket (all else held equal) and you get a range of 28.8 to 88.4 gear inches. It's true that you could get the Sturmey-Archer down into the Nexus territory with a 28-tooth chainring, but it's my understanding that such a small ring would probably result in rapid wear of the ring and chain (though perhaps I'm mistaken about that). Moreover, the OP, who has an old 3-speed, probably doesn't have a crank with replaceable rings and thus would have to buy a new crank and maybe a new bottom bracket. This problem would be exacerbated if the OP's wheels are larger than 26 inches. So, I don't think it's nonsense to say that the Sturmey-Archer hub is better suited to small-wheeled bicycles (and actually I was just echoing Sheldon Brown's judgment on that). But it is not the HUB that is unsuited to small wheels, it's the rest of the kit. (And chain wear is not made worse by small sprockets until you get into the 11-12-13 tooth range; though 11's have been used on SA multi-gear hubs, and I run a 13 on the Nexus.) The OP would like to run a 8ish-speed gearhub on a large-wheeled (26"-29") bike. If they choose a Sturmey-Archer hub, they will have to use a strangely large cog or a strangely small ring to get the usual sort of gearing. On a small-wheeled bike, that same hub gives gearing in a pretty typical range using cogs and rings in quite mainstream sizes. Indeed, the gearing issue for small-wheel bikes is such that Shimano actually built a special hub and cassette with the ability to run a 9-tooth small cog: http://www.sheldonbrown.com/capreo/index.html So in short, the Sturmey-Archer 8 hub is well-suited to small-wheel bikes because it allows use of readily available gearing sizes. On bikes with larger wheels, normal sorts of gearing options require weird gears. I do have a 64-tooth ring in my Pile, but it's hardly the sort of thing I expect the local shop to stock. -- Ryan Cousineau http://www.wiredcola.com/ "In other newsgroups, they killfile trolls." "In rec.bicycles.racing, we coach them." |
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