I'll admit that I'm a bit obsessive when it comes to mechanics. Bicycles included.

This is about my 2010 Schwinn Madison. I notice that when I slide my rear wheel into the dropouts (or track end) it doesn't sit perfectly centered between the stays (both chain and seat). I can get it centered if I move it about a bit and hold it as I carefully tighten the axle nuts. I measured the frame alignment as per Sheldon's string method, and I get 31mm on the button from the seat tube on each side.

The bike rides just fine. I can ride straight with no hands, and it doesn't show any other symptoms of misalignment other than the wheel not centering in the dropouts without a little tweaking.

Anyone else have this issue? It bugs me a bit, but that's because I'm obsessive and I really appreciate accurate manufacturing.

Well,sometimes thats life.Can't expect precision on the lower end.To get the cantis to work on my '85 Le Tour luxe I had to play with the hub spacing to center the wheel between the seatstays due to one being 2mm longer,leaving the wheel a bit tilted.

It may be your wheel and not your frame. Are you certain your wheel is dished properly?

Yes. Positive.

Since it rides well, and the rear triangle isn't off to one side, perhaps this little problem could be improved with a file?

Axle, perhaps.

To expound, the axle itself may be askew. Happens a lot on the lower end, and don't even get me started on the box-store hubs---they are glaringly obvious. If you're really OCD, you can work up a temporary jig with those laser levels to really key in on the alignment of the frame.

Would check the wheel and components before taking a file to a seemingly solid frame.

Since you can center it yourself and it rides fine, I wouldn't change anything.

This.

I would file until I'm satisfied. And regret it later

If you just ordered/ bought it from a store/ site; I say it's time to RMA/ exchange it....

You're smarter than that right?

screw the file, take an angle grinder to that isht.