My rear wheel is a flip/flop hub installed on horizontal dropouts. The nuts are tight. The hub seems to shift back and forth on the axle though. I can grab the top of the wheel and move it side to side till it hits either side of the brake pads.

Does this mean the rear hub is trashed and I'll need a new wheel?

Are the cones adjusted tight enough?

Tighten the cones with cone wrenches or eventually your hub will be trashed. Parktool.com has good DIY instructions.

Only two possibilities. Spokes are very loose or the hub bearings are very loose. Roger

Sounds like the hub needs an overhaul and adjustment. And the spoke-tension should also be checked.

Not that I'll add anything new, but this is a bearing adjustment issue. And if you can move the rim that much, it could be trashed. You won't know until you tighten the cones up and see how she spins.

Here's a link to a video that shows you how to overhaul a hub and adjust the cones:

https://bicycletutor.com/overhaul-wheel-bearings/

And here's the Park Tool Repair written version:

https://www.parktool.com/repair/readhowto.asp?id=105

Tighten the cones.

I didn't bother to read the other posts. Did anyone mention the cones?

Yes. All 7 posts before you mentioned the cones.

^I still haven't bothered to read any of the posts. Did anyone answer my earlier question?

Even the rhetorical questions are answered on Bike Forums.

I'd answer you, but I didn't bother to read your posts either.

Well that was a pain in the ass. Had to remove both the fixed cog and freewheel which was not fun as the fixed cog and lockring were put on with blue loctite. I've never messed with cone adjustment before, but it was tricky. I put some blue loctite on the cone lockrings so they don't come loose again - the wheel didn't wobble before recently and since just riding managed to loosen up the cones, I figured I wouldn't chance it.

Everything is back together now and she rides good. Hopefully the loctite will keep them from coming loose again.

Thanks.