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Converting cassette to 3 speed hub ?
#1
I'm new...here.
I want to re-lace my wheel and change-out the 8 speed cassette and hub for a 3 speed, with brake, on a 24 speed touring bike.
I don't need all the gears, and I'd end up with a 9 speed bike I guess.
I really could use the extra brake in the 3 speed hub as I travel heavily loaded and don't have disk brakes.
Anyone done this, any ideas ? I know I'll need a chain tensioner already.
2008 Specialized Globe commuter converted to touring
james
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#2
So 3 speed internal in the back and 3 chainrings in the front? I don't think that will work very well due to chainline issues and the amount of slack you'd have to adjust for in the chain. I think you would also end up with a very wide gear range with huge jumps between each gear.

When people want to reduce the total number of gears and simplify a bike, they usually take off the front derailleur and just go single in the front, but leave the rear gears alone.

Is the main issue that you want a hub brake? If you can lock up your rear wheel with your current brakes, a hub brake won't be anymore powerful. But they are better when you have to brake for long periods as they don't build up heat in the same dangerous way and work a little better in wet conditions than rim brakes. If you want more braking power, you may be able to upgrade your existing brakes and get some improvement.

Maybe give us a better sense of what you want to achieve.
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#3
why not look at an 8 speed hub;
http://www.sturmey-archer.com/products/hubs
http://activesport.co.uk/shop/article_HUSTS8U6/Sturmey-Archer-X-RD8-8-Speed-Rear-Hub.html?shop_param=cid%3D2380%26aid%3DHUSTS8U6%26
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#4
Can't lock up brakes when loaded and i have pretty good brakes...I looked at chainline issues also, I think it would work..and I may have to drop a ring gear off the front
i met a rider in Argentina who did this and loved it, but he had a close ratio
3 speed hub...some problems with his top ring gear ratios but overall he was happy with the extra braking...had ridden all US and down to AR this way
James



(06-01-2012, 12:18 PM)DaveM Wrote:  So 3 speed internal in the back and 3 chainrings in the front? I don't think that will work very well due to chainline issues and the amount of slack you'd have to adjust for in the chain. I think you would also end up with a very wide gear range with huge jumps between each gear.

When people want to reduce the total number of gears and simplify a bike, they usually take off the front derailleur and just go single in the front, but leave the rear gears alone.

Is the main issue that you want a hub brake? If you can lock up your rear wheel with your current brakes, a hub brake won't be anymore powerful. But they are better when you have to brake for long periods as they don't build up heat in the same dangerous way and work a little better in wet conditions than rim brakes. If you want more braking power, you may be able to upgrade your existing brakes and get some improvement.

Maybe give us a better sense of what you want to achieve.

There's an idea, might be out of my price range though- I could drop the front ring gears off and go with one this way
thx I'll explore this more
James


(06-01-2012, 12:38 PM)trevgbb Wrote:  why not look at an 8 speed hub;
http://www.sturmey-archer.com/products/hubs
http://activesport.co.uk/shop/article_HUSTS8U6/Sturmey-Archer-X-RD8-8-Speed-Rear-Hub.html?shop_param=cid%3D2380%26aid%3DHUSTS8U6%26
  Reply
#5
(06-01-2012, 12:59 PM)jameson2wheels Wrote:  but he had a close ratio
3 speed hub...some problems with his top ring gear ratios but overall he was happy with the extra braking...had ridden all US and down to AR this way

Interesting. I think the "close ratio hub" issue is fairly important. A standard 3 spd is meant to offer a full range of useful ratios with one front chainring. But if you have two fairly close chainrings in the front, it may give you a good overall range with adequately small increments between gears.

I've never done any loaded touring. I know hub brakes are popular for long descents where you could overheat a tire with a rim brake and for wet conditions. Just the standard disclaimer that for rapid braking, your rear will never be as powerful as the front anyway. But again, there's reasons for a hub brake beyond peak stopping power.

Looking at the 7+ gear hubs might make sense. I've heard they have a little more internal friction than the 3 speeds. But it is a more direct way to address what you want.

Keep us updated - an interesting project.
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#6
So far it seems the toughest hub in my price range would be the sturmy - so I'm looking that way. Maybe it just requires doing it and sorting the front rings later.
Thanks for input
James

(06-01-2012, 02:27 PM)DaveM Wrote:  
(06-01-2012, 12:59 PM)jameson2wheels Wrote:  but he had a close ratio
3 speed hub...some problems with his top ring gear ratios but overall he was happy with the extra braking...had ridden all US and down to AR this way

Interesting. I think the "close ratio hub" issue is fairly important. A standard 3 spd is meant to offer a full range of useful ratios with one front chainring. But if you have two fairly close chainrings in the front, it may give you a good overall range with adequately small increments between gears.

I've never done any loaded touring. I know hub brakes are popular for long descents where you could overheat a tire with a rim brake and for wet conditions. Just the standard disclaimer that for rapid braking, your rear will never be as powerful as the front anyway. But again, there's reasons for a hub brake beyond peak stopping power.

Looking at the 7+ gear hubs might make sense. I've heard they have a little more internal friction than the 3 speeds. But it is a more direct way to address what you want.

Keep us updated - an interesting project.
  Reply
#7
What type of hub brake will this be? If it is the normal "pedal backwards to brake" type: You cannot do this with more than one chain ring, as you need something to tension the chain correctly and you'll bend this thing when braking... the Sturmy Archer hub looks like it works this way, so be careful.
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#8
I would arrange a tensioner ro maybe leave the derailleur tensioner on to accomplish this'still looking at all the angles - wish I had a foto of the pesky krauts' bike in Argentina who had this setup. NI can't remember if he used the pedal brakes or if his was sans brakes.




(06-03-2012, 07:51 AM)Joe_W Wrote:  What type of hub brake will this be? If it is the normal "pedal backwards to brake" type: You cannot do this with more than one chain ring, as you need something to tension the chain correctly and you'll bend this thing when braking... the Sturmy Archer hub looks like it works this way, so be careful.
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#9
SA 8 spd. has a lever operated brake; pt no. X-RD8(W)
http://www.sturmey-archer.com/userfiles/manuals/XRD8-Tech.pdf
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#10
It sure does, that solves a problem- I've read a few places there have been some problems with this hub...not sure how it will stand up to 10000+ miles of heavy touring.

here's the correct linky: http://www.sturmey-archer.com/products/hubs/cid/5/id/7/tech/1
  Reply
#11
I don't know the new SA 8 speed hub, but I am familiar with several of the nexus and Sram 7 speed hub models. It seems Sram have less trouble with every day use, all kinds of weather. Somehow they rust less and water doesn't seem to enter the internal parts that easy. Some Nexus models are good, but many of them have had issues with the capsule that protects from dust and water to enter the system, and it really ruins the whole thing. It is hard to find a guy who knows how, and are willing to do a proper cleaning, regreasing and repair a faulty hub. What most often fails in the Nexus hub beside water, rust and proper care, is the brakes (coaster/pedal type). It consists of two or three cone shaped parts held together with a metal spring, and it either breaks or goes out of place. This cone shaped brake part is much smaller than what you might be used to see in a single speed or older three speed hub. Sram models seem to have less trouble with this. These hubs are generally very good, and long lasting though.
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