budopo

Ok, two unrelated (most likely) issues. The bike is a 1991 Davidson Impulse, Shimano RS-80 clinchers, Dura-Ace rear derailleur and shifters (downtube), Suntour Superbe Pro crank, KMC chain.

First issue: I fine tune the hub preload by very small adjustments to the quick release skewer (I adjust the cones pretty well and use the skewer to get the preload just right). I'll tighten the skewer, grab the rim, and see if I can feel any play. The amount of play depends on where I grab the rim, though. I can adjust the skewer perfectly so that the play disappears just as the skewer is fully tightened, but if I grab the wheel elsewhere on the rim, there'll be a touch of play. If I grab the rim 90 degrees from the valve, it's fine, but grabbing at the valve or 180 degrees from it, and I'll feel a bit of play. I tighten the skewers to get rid of that, by the way (so maybe a bit too much preload overall). I repacked and adjusted the hubs, and replaced the freehub, but not the axle.

Second issue: Every so often, my chain will skip. I replaced the chain and cassette, and it still happens from time to time. The chainrings look fine (no sharkfin shape that I can see). It usually occurs when I start to put on a bit of power, but also sometimes when I'm cruising, pedaling pretty smoothly (the skip doesn't happen to often, so it's hard to find a pattern). It hasn't really happened much recently, so maybe the new parts needed to settle in.

I'd appreciate any advice. Thanks in advance.

FBinNY 

Hub adjustment.

It isn't that rare for some ovalness to develop in hub bearings, especially if you're lucky and have ridden miles on miles without a flat. The wheel spins round so the hub shell cup tends to wear fairly evenly, but the axle is stationary, so the cone wears unevenly as the chain load and bike's weight combine to increase wear on the top and rear of the right con, and top of the left.

That can cause some inability to perfectly adjust the bearing, but it's usually not dependent on where you test with respect to the rim, but in stead according to the frame (axle), ie. top/bottom vs, front/back.

Either way, this is a bicycle, not a rocket ship o airplane engine, so get the best adjustment you can, and don't obsess over it.

Skipping

Ocasional chain slipping in the rear, especially with a new chain, also isn't that rare. Under load the chain is pulled forward vs. the sprocket, so the arc of engagement over the tips of the teeth has a tight (or no) clearance over the corners, and the chain can climb up instead, where it rides for a short distance until it's back in phase and drops in, causing a skip. This is where some wear is your friend. With wear, especially on tooth corners, and roller play, allows the necessary slop that makes this less likely if it happens at all. As you note, it seems to be improving, so I'd put it out of your mind and not worry until/unless it gets worse.