Axle Keepers
 

Paulcomp has axle keepers that push from the crank side of the drop outs. Today I saw a bike with some axle keepers that slipped around the drop outs and had a screw that pushed from the back side of the drop outs. First, does anyone really need axle keepers for general street use? Second, if so, which side shoud they push from? It of course seems like the paulcomp ones are good to keep the chain from getting too much slack, and the other ones would keep the chain from getting too tight. I don't see that very many people use either.

Are you talking about chain tensioners?

I think those are actually just paul track ends that you have to get built into a frame.

http://www.paulcomp.com/drop.html

I could be wrong.

They seem like they would be annoying, as you'd have to either use a master link in your chain or back out the screws to loosen your chain enough to get it off the cog/chainring.

The paul style track ends and the chain tensioners that you attach to the dropouts are both doing the same thing; the paul is pushing the axle back, and the chain tensioners are pulling the axle back. Both lead to a tighter chain as you turn the screws

both of them pull/hold the axle back.

http://www.domenicscycling.com/images/mks_tens.bmp

This is the style that most people use. I reckon both of them require backing off the adjustments to remove the rear wheel if they are adequately tight.

You don't really need to use them. They help in getting the wheel installed straight and with a good amount of tension, but I think a lot of people end up using them to over-tension the chain, which wears out all of your drivetrain pretty quickly. They can provide a little bit of insurance, should your axle nuts slip, but they aren't necessary.

those MKS's above have to be loosend to remove them , hense you have to start all over again aligning the wheel before tightening down, pain in the ass!

From my experience all you need are track nuts and a steady hand for alignment.....but I'm a cheap bastard and use the cheap bastard logic.