So I don't exactly know when this started, but the other day I sat up straight to ride no-hands for the first time in a while, and almost fell over. The bike wanted to lean to the left, hard. I tried again and managed to get upright, and I can go along, but I have to lean my body way to the right to balance the bike going the other way.
This is a 60cm crosscheck, which I've been commuting with all year. Near the beginning of the year, when I had some pinched nerve issues, I had to do a lot of hands-free riding so I could stretch, and I never had this problem. But that was with a whole different drivetrain and wheels. Since I
rebuilt, I can't remember whether I've had occasion to ride hands-free, seems like I must have, because it's been at least a month of daily commuting and some longer rides.
I first noticed it with my rack & small bags on (although my typical load is quite small: a polo shirt, socks and underwear, and maybe lunch). This morning with the rack&bags off, I tried again, still leaning. I don't think it can be a weight distribution issue because if anything, bikes are heavier on the right side, what with all the drivetrain over there, and I don't have an asymmetric skeleton (I know all people are asymmetric to some extent, but I'm "normal" as far as I can tell)
I checked the wheels, they seem quite well centered in the fork and stays.
Before this happened, I never noticed the bike pulling to the left (even when I ride hands-free, even though balance is akimbo, the bike runs straight), now that I'm thinking about it, maybe I can feel a little more pressure in my right hand on the bar to keep the bike up, but it may well be my mind playing tricks on me.
Any ideas what can be causing this, and how to resolve it, or other tests I can try and report back?
UPDATE: Problem solved, overtightened headset with detent, thx to bent-not-broken (&all others), see my ONE THOUSANDTH POST below