Commuting - Tensioner for Crosscheck/nexus8

Lately, my wheel has been sliding forward and I have to pop the chain back, which is a total hassle.

Would a tensioner fix this problem? Which one should I get?

Properly tightened, your wheel shouldn't move in the dropouts. Check the knurling (texturing) on the axle nuts and make sure they haven't worn down smooth from sliding about. If they have, replace them and you shouldn't have any more problems if they're tightened far enough.

Make sure you have the correct anti-rotation washers installed, and each of the anti-rotation washers is installed on the correct side.

Shimano makes anti-rotation washers for vertical dropouts, track dropouts, and forward-facing semi-horizontal dropouts.

You aren't by chance using quick releases on your rear wheel are you?

You aren't by chance using quick releases on your rear wheel are you?

Nexus has a solid axle. Impossible.

I don't think a chain tensioner would help with this. I'm going with a little more torque tightening the axle nuts. Sometimes I think they are tight enough, but later find that they are loose. Perhaps there was a snag on a part of the axle thread and the drop out or something. So after tightening try riding lightly a few yards and then retighten the axle nuts. If you have a stubby wrench, maybe try a longer one for more torque. This has happened to me a few times too, and just a little more torque seems to have stopped the wheel from sliding.

Also I've found that one of the inner hub nuts (#28 - lock nut for left hand cone on page 29 of Sheldon's manual) (http://www.sheldonbrown.com/nexus8/pages/29.htm) tends to loosen every time I take off the wheel so I need to retighten that every once in a while. If you hold the top of the wheel and push/pull left to right and there is some wobbling you might want to check this one.

chain ring in between the ring and cog, just let it float :)

I've tightened the nut so much it got deformed. Are there replacements available?