Threadless headset adapter for 1981 Raleigh
 

Recently became aware that these adapters exist, but have one concern. Last time this bike was in a shop, the mechanic adjusted the headset, and told me the headset might not be able to be adjusted again, as in it is about worn out. Not sure what the specific issue is.

I wonder if putting in a threadless adapter would likely eliminate the problem, or whether the problem would persist. Sorry, I don't know how threaded headsets wear out.

What are the critical factors when purchasing an adapter? And can I assume the old forks and streerer tube can stay, since there are no issues with steering? Recommendations for a value oriented model adapter? I'd like to be able to use a modern stem and handlebars.

No, the threadless adapter is for letting you use stems for threadless headsets with your threaded head set. At least the adapters I'm familiar with are.

If your threaded headset can't be adjusted again, then something will have to be replaced. Did they say whether it was because of the threads being damaged on the steerer tube or was it some other reason? If they didn't say, can you ask them if they remember why?

As Iride01 mentioned first you need to determine what the mechanic was referring to when he said it was worn out. Was it the threads in the headset nut or threads on the steerer tube or was it just the bearings and races were worn. If your fork tube threads are fine you can just install another threaded headset and use the threadless stem adapter for threaded quill forks. quill aheadset adapter - Google Search

A threadless adaptor is just a different stem and has nothing to do with the headset itself.

Innicycle, headset and threadless adapter in one.

Sorry, fifteen years or more since mechanics input. Memory not that good. What are threads on steerer tube for? I thought the threaded headset wedged against inside of steerer tube, essentially doing what the stem clamps do on threadless, that is holding the steerer tube so there's no play at races/ bearings.

It is likely that a 40 year old Raleigh has weirdo threads on the headset. It might be difficult to source a replacement.
I tried to install a new headset on an 1980 Raleigh Grand Prix and realized the problem after I had the frame cups pressed in.
I stole the bearings from the new headset and re-installed the old Raleigh headset.

To properly install a threadless headset you need a new fork with a longer unthreaded steerer. There might be a way to use some threadless adapters to install a threadless headset on a threaded fork, but it will take some ingenuity, confidence, and the realization that you are responsible for your own safety with such an off-label application of the adapter. A box of spare parts and an understanding of how headset bearing adjustment works will also be useful.

The stem is not involved in headset adjustment on a threaded headset - the threaded locknut does that and the stem has a wedge or expander to grip the inside of the fork's steerer tube.
On a threadless headset the stem holds the bearing adjustment in place.

I believe you are looking for one of these. https://www.thebikesmiths.com/produc...%20%26%20Stems

Your local bike shop can order you one or you can try these folks.

I don't believe we can say for certain exactly what the o.p. needs because they have not given sufficient insight to the issue (if any) that is being presented. Just about anything within reason can be found on Ebay to keep those legacy icons running.

To convert a bike from threaded to threadless requires replacing the fork, and also is not likely to reduce wear.

Replacing with a new threaded headset isn't that difficult or expensive, particularly for a professional mechanic with shop tools. I'd quote it probably 30-40 minutes of shop time. If it's your 1981 Raleigh, it almost certainly isn't that hard. Earlier Raleighs had their own headset standards, but by 1981 it's almost certainly either ISO or JIS, which are the two more common standards for a threaded headset.

Don't be so sure - many Raleighs were built in old facilities using old tooling up until the mid Eighties. My c. 1980 Grand Prix has nonstandard threading on the fork. All other dimensions (ID, crown race seat, OD) are standard but a new ISO 1" headset would not thread on.

You would probably need a new fork.
Because the stem goes on the outside of the fork steerer rather than inside.
But you could use a threadless stem adapter If you wanted to use a modern bar and stem.
They don't look pretty.
I think it would be incredibly difficult to wear a headset till there was no more adjustment.
Metal would have to be grinding against metal.
It is more likely the mechanic had to bodge a fit with spare parts he had.

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