If you're wondering if you really need one, then you probably don't. You would've noticed your chain slacking before questioning it's necessity.
Does it make your ride look better? Chain tugs always make your ride look tuff.

I use some old GT tensioners that are super easy to adj.
Also makes it a little tougher for my rear wheel to get stolen, You need a small allen wrench to get it loose.

Chain tugs are just one more thing to get in the way when I've gotta flip the wheel.

I use those redline ALU ones from danscomp and I have to say....avoid em. I don't know if it's just me but a lot of people on these boards use em which is what prompted me to order a pair (that and they're cheap 9.99). My issue with them is the actualy back plate that locks the whole hub/wheel assembly from moving forward on the chain tensioner is rather weak and cheap feeling. That and they have some vertical play while sitting in the dropouts.

I bought em primarily because I didn't know if the MKS ones work with KHS flite 100 trackends, and still don't. Someone out there has to know. If they do, I will be ditching these redline ones as soon as that information is available to me =)

i have found that chain tensioners are so worth it. I use a pair and it makes centering and tightening perfect every time. As well, as an added bonus it does make it tougher for someone to steal your rear wheel

I've been using a tensioner (surly tuggnut) for over a year, and I ride almost every day. Even though everything seems tight and tensioned perfectly, I am still having to readjust the tension every few weeks. Any danger of over-torquing the nuts? Is it possible that the tuggnut is not holding position? Thanks in advance for any insight.

http://www.universalcycles.com/image...small/4091.jpg
So much cuter than a tuggnut, yet still with the bottle opener feature.

Chain wear?

Using the standard measure of chain wear ( www.sheldonbrown.com/chains.html ), my original one is still OK (~7,500 miles).

I have a Surly Tuggnut, and it does the job.

The bottle opener feature is nice, too.

ok--dumb question--whats the difference between those "chain tensioners" in the photos above and those long pulley-type "chain tensioner" on singlespeed bikes?

these pull your hub back in a horizontal dropout.
those other ones are for tension when you don't have a horizontal dropout.

I use mks's on my fuji track for street. they work great and they look really sweet... they are pretty sleek. I much prefer them to having some giant monster on my bolts.

I have a track bike with your normal horizontal dropouts and I use the MKS tensioners. Love them. But my friend has a converted road bike with the vertical, slightly facing forward, standard road bike dropouts on his fixed. How do these chain tensioners work for a road bike convert like that? Can you please post some pictures of them on your convert and explain how they work? We've been racking our brain trying to think of how we can make/get some chain tensioners that would work with his converted fixie.

echoed. Mine broke in the same manner. Lame lockring.

But, as has been said, the bottle opener is key.

Nevermind. I didn't see the picture before showing how those chain tensioners worked for converted fixies. Just saw the picture now. :)

I use a pedal wrench to tighten my track nuts. I've never had any problems with them getting loose.