Originally Posted by
JohnDThompson
If the cup is aluminum, it's unlikely to have damaged the steel steer tube threads. This is a Good Thing, as it's generally easier and less expensive to replace the headset than to replace the fork. There are plenty of threaded headsets still available, e.g. the Tange "Levin," Velo-Orange, etc. Tange even makes a threaded headset with roller bearings in the lower cup for better handling of the thrust loads headsets must take in use. Keep the new headset properly adjusted and the threads will stay intact.
The binding the OP describes is indicative of the cups not being perfectly parallel, either because they are not fully seated or because the head tube needs milling and facing. If you have a cup press, you can try re-seating the cups. If that doesn't help, it's time to take it to the LBS for milling and facing.
John- All you say is true in my experience. BUT... (there's always a butt) If the HS does loosen and the threaded top cone/cup is steel then the steerer is at risk of thread damage. Which is harder/ the steerer or the bearing piece? There were a number of Japanese HSs with a mix of alloy top nuts and steel top cups/cones.
Also WRT the roller element HSs. I've used StrongLite A9s for many years (just finished a 4 day tour with one) and they are even more sensitive to frame prep and HS installation (as you already know), if there is a frame/fork issue that places the HS parts off parallel then the loose/tight problem just worsens. I'll add that they are susceptible to notching when ridden loose, their conical steel rolling surfaces are (I suspect) made of soft steel. The attempt to get a freely rotating HS adjustment can often result in a loose HS, given their greater rolling friction (compared to a balled HS). Once again an "improvement" can result in a shifting problem.
Always cynical until proved otherwise, Andy.