Graham wrote:After a terrifying high-speed wobble, down a long, steep hill I determined that headset was a likely major factor.
H/S races heavily brinneled with Bars-straight-ahead-position sitting between equilibrium points on either side...
...If anyone is just at the start of such a problem, before the races get very battered, a short-term fix exists:
Pop the three races that aren't screwed in (crown race, head tube bottom and top race out and put them back in, each rotated by a different amount but none of them by 180 degrees. Say, 30, 40 and 50 degrees. The screw-on one will end up in the same orientation as it started.
This means that the brinneling in each race is angle-offset from all the others or "out of phase", which significantly reduces the "straight ahead self-centering" effect.
This does require headset installation tools, and if you have to go to the LBS, the labour might be so much that you might as well buy a new one. But if you can somehow get it done cheap, or free (I used to be a member of a club with a workshop with workshop tools, maybe you can find such a club) then it can be a solution lasting a fair while and is useful for those of us either short of cash or crying about the expensive but dying headset (I did this on a Campag Record one in the late '90s)