# How to use an old rear derailleur as a chain tensioner



## dgangi (Jan 19, 2004)

The link to Keith Bontrager's column in the SS FAQ, where he describes how to convert an old derailleur to a SS chain tensioner, no longer works -- I am taken to a Bontrager page that states the requested web page is no longer available.

I am in the middle of converting my '97 Trek 8000 into a SS and would like to use my old XT 8-spd derailleur as a cost-saving measure instead of buying a chain tensioner. Can anybody give me the basic instructions for how to do this?

Thx...Doug


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## sportsman (Mar 2, 2004)

dgangi said:


> The link to Keith Bontrager's column in the SS FAQ, where he describes how to convert an old derailleur to a SS chain tensioner, no longer works -- I am taken to a Bontrager page that states the requested web page is no longer available.
> 
> I am in the middle of converting my '97 Trek 8000 into a SS and would like to use my old XT 8-spd derailleur as a cost-saving measure instead of buying a chain tensioner. Can anybody give me the basic instructions for how to do this?
> 
> Thx...Doug


A simple way.. run a piece of cable through the derailleur (just to provide some tension, use the end with the cable stop). Then you use the barrel adjuster and the derailleur in/out adjustment screws to correct your chainline.

have fun


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## dgangi (Jan 19, 2004)

*Aligning the pulleys & cog*



sportsman said:


> A simple way.. run a piece of cable through the derailleur (just to provide some tension, use the end with the cable stop). Then you use the barrel adjuster and the derailleur in/out adjustment screws to correct your chainline.
> 
> have fun


Actually, I was able to align the pulleys of the rear derailleur with the rear cog using the "+/-" adjustment screws. I figure this is more trouble-free than having to rely on the barrel adjuster and a piece of cable.

My biggest question is this - how short do I make the chain? With a traditional horizontal dropout/BMX frame, the chain is tensioned by pulling the wheel back, thus giving an indication on how short to make the chain prior to tightening it. But with a derailleur as tensioner in an old gearie, I'm not sure how many links to remove as the derailleur has the capacity to remove a *lot* of slack. Do I remove enough links so that the derailleur is extended 100% when the wheel is in place (i.e. as fully extended as it will go)? Or would this risk breaking the springs in the derailleur? Should I leave enough slack in the chain so the derailleur isn't fully exended when the wheel is in place? Am I making any sense here?

Thx...Doug


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## sportsman (Mar 2, 2004)

I used to run my chain pretty darn tight, as tight as I could get it. It worked for me.


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## Nat (Dec 30, 2003)

sportsman said:


> I used to run my chain pretty darn tight, as tight as I could get it. It worked for me.


Same here. Here's the best pic I could dig up:


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## hu-man (Jan 13, 2004)

sportsman said:


> I used to run my chain pretty darn tight, as tight as I could get it. It worked for me.


Run it tight - stretched out - or not. Its a derailleur so it works in a variety of positions. I've never had any problems either way. You can use an old road derailleur too, for the shorter cage, less flex and less chance of getting caught by a stick.


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## hu-man (Jan 13, 2004)

dgangi said:


> Actually, I was able to align the pulleys of the rear derailleur with the rear cog using the "+/-" adjustment screws. I figure this is more trouble-free than having to rely on the barrel adjuster and a piece of cable.
> 
> My biggest question is this - how short do I make the chain? With a traditional horizontal dropout/BMX frame, the chain is tensioned by pulling the wheel back, thus giving an indication on how short to make the chain prior to tightening it. But with a derailleur as tensioner in an old gearie, I'm not sure how many links to remove as the derailleur has the capacity to remove a *lot* of slack. Do I remove enough links so that the derailleur is extended 100% when the wheel is in place (i.e. as fully extended as it will go)? Or would this risk breaking the springs in the derailleur? Should I leave enough slack in the chain so the derailleur isn't fully exended when the wheel is in place? Am I making any sense here?
> 
> Thx...Doug


The barrel adjuster and the peice of cable allowed you to fine tune the alignment. You can also run two cogs in the rear and switch between them by turning the barrel adjuster.


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## whoda*huck (Feb 12, 2005)

*But that would take your bike OT*



hu-man said:


> The barrel adjuster and the peice of cable allowed you to fine tune the alignment. You can also run two cogs in the rear and switch between them by turning the barrel adjuster.


wouldn't it?


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## hu-man (Jan 13, 2004)

whodaphuck said:


> wouldn't it?


If you have to ride to the trails, or ride a variety of terrain, having a bike with 2 single speed options is one way to go. I have mine set up with a 34 ring and 17&20 cogs. I chose one or the other SS gearing and live with the choice.


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