I have a little chaintug on the end of my driveside dropout (forkend, whatever). I use it, and after 15 mins or so of fiddling around with my chain tension and wheel alignment, I can get it to a nice sweet spot where the chain doesn't bind and there is no slack when I go from forward pedaling to back pedaling.

Afterwards however, when I take it out for a ride, the chain starts making painful noises, and then the slack returns. What do you all think is happening? How to fix it? Is it possible to find that sweet spot and remain there indefinately, or is some slack inevitable? Do I need a better chainring (I'm currently using a stronglight)? Or will it be fixed by centering the chainring on the spider somehow? Or maybe the chain is somehow to blame? Maybe I just need to torque the axle nuts harder? Thoughts?

One possibility is that your chainring isn't round at all so your setting the tension at the widest part and, when you get to the narrowest part of the ring theres slack there.

However, I would say its most likely that your wheel is moving in the track ends/dropouts. Not too sure about the horrible noise part though - that maybe the chain tug shrieking as its being asked to do all the work.

Some hubs have notoriously bad track nuts that just don't do jack. I would probably upgrade your nuts if they came with a cheap hub. Other options are to rough the paint around the ends/dropouts so the surface isn't so smooth or try with a friends wheel to see if you have the same problem.

If this is an Alu frame be careful about cranking down your nuts too tight.

dude,

It could be the nuts maybe--the hubs are promax fix-fix, and I dont torque them SUPER hard because I've stripped promax axles before. But I torque them pretty hard. The chainring is a stronglight "Track" chainring, so I would imagine that it is pretty round, but what do I know? It could be a very minor centeringness issue with the spider, but everything looks nice and even.

Sheldon Brown has a method for evening out your chain tension. I've never gotten his specific method to work, but I have used similar methods and had it work pretty well.

Do you have chain tugs on both ends? Maybe the non-drive side is slipping.