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Discussion Starter · #1 ·
Hey all,

I'm building a singlespeed that I plan on using as a commuter and trail bike. I'd like to be able to use a large (42t) chainring and a smaller (34t) chainring so I can manually shift between them for street or trail use. Has anyone done this before, and can it actually be done?
 

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I can be done , you will need a tensioner or have to shorten chain when you change chainrings .
 

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yes. you'll need an old derailer or a tensioner.
or you can go with a dos eno cog or do a homebrew.
but if you want to run without a tensioner you'll need to lower the step in front to match whatever step you have it in the rear. so you might get a 36 / 34 to work...

 

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It would be easier (if you have a cassette-style hub) to run two rear cogs and one ring. If you put a 34t up front, a 16t / 20t rear would give you basically the same gear range you are looking at, and the tensioner would have to take up much less slack. Of course, you might have to move it laterally a bit to run smooth as you change the position. Nothing a turn of a screwdriver on an old derailleur stop screw wouldn't handle!
EDIT: Gear range is not the right wording - "percent jump" might be better... Of course, those might be good gears for you on a 29" SS anyway..
 

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Discussion Starter · #5 ·
Thanks for the tips. I'm going to try the 2 chainring setup first since I don't have any single chainring bolts at the moment. If that setup doesn't work too well, I'll fork out the $10 for single bolts and try the two rear cogs instead.
 

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you could get an old two speed kick back hub ...:p
 

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An 8 tooth difference means you have a lot of chain for a tensioner (or fixed derailer) to take up.

Many do great with 2x2, or dinglespeed. Something like 34/18 and 36/16, where the number of teeth remains the same. That way there's little difference in the chain length you need.
 

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nuck_chorris said:
If you can find one
land of enchantment has tons of vintage bikes ...i have owned two myself but there are a few to be had in alb ...:thumbsup:
 

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Get a casette hub and run a dinglespeed. Run maybe a 32/16 (2:1) for offroad and a 36/12 (3:1) for onroad and you'd have the same chainlength, you'd just have to stop and move the chain from the inner ring/cog to the outer ring/cog.

I'd suggest trying to find a bike co-op in your town or make friends with a guy at your LBS so you can get 2 rear cogs, casette spacers, and a lockring on the cheap. Or be able to borrow a couple of different rings and cogs until you find the two gears that you like.
 

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local trails rider
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GTscoob said:
36/12 (3:1) for onroad
A 12 tooth cog is pretty small. I suspect it is small enough that it is less efficient and wears out faster than a bigger cog.

Notice that the number of teeth is not the only thing that affects chain length. The angle of the chain from chainring to cog makes a difference too. Sometimes that difference is enough to affect your setup.
 

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I did initially set up my SS 29er as dinglespeed. It was 33/19 + 36/16 and worked great. I think this kind of 2x2 setup is far superior to 2x1 or 1x2 setup because you don't need a stinking tensioner. Of course the downside is that you have to stop, loosen the rear wheel and get your hands dirty.
 

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kide said:
I did initially set up my SS 29er as dinglespeed. It was 33/19 + 36/16 and worked great. I think this kind of 2x2 setup is far superior to 2x1 or 1x2 setup because you don't need a stinking tensioner. Of course the downside is that you have to stop, loosen the rear wheel and get your hands dirty.
yeah but it takes like 2 second and you can do it with your thumb and index finger..when im done i just wipe the grease on the chainstay LOL
 

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dustintendo said:
it takes like 2 second
I saw kide do the switch, and it took more than 2 seconds. Not much more, though, and definitely not long enough to matter when we were getting the group together for the trails :thumbsup:
 

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I'm sure you can do it in half a minute. Might take two if you hurry.
 
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