Bicycle Mechanics - Thingamabob stuck on cantilever mount (with photo)

I got a used cyclocross frame. Had it over a week now, but only noticed now that the cantilever mounting point had these things stuck onto it. I'm not sure what they are and they are absent on the mounts on the fork. I was able to slip one right off, but the other one is stuck. I can twist it clockwise and counter-clockwise endlessly, but it's not screwed on.

In the photo, you can see me holding the one that slipped right off. What is it and how do I get it off? Thanks for any help. Definitely don't want to damage the frame in the process.

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I got a used cyclocross frame. Had it over a week now, but only noticed now that the cantilever mounting point had these things stuck onto it. I'm not sure what they are and they are absent on the mounts on the fork. I was able to slip one right off, but the other one is stuck. I can twist it clockwise and counter-clockwise endlessly, but it's not screwed on.

In the photo, you can see me holding the one that slipped right off. What is it and how do I get it off? Thanks for any help. Definitely don't want to damage the frame in the process.



That looks like the bushing from the inside of an installed cantilever brake. They're of no use to you without the rest of the brake, and the original owner is going to have a heck of a time getting the old brakes to work without that bushing. The one that's "stuck" should come off with a little force- try lightly tapping it off from behind with a screwdriver and a hammer.

I know of at least one brake design where those were supposed to be installed with a retaining compound, so if it won't budge, try carefully heating it. Key word: carefully :)

Almost looks like the pivot out of a Paul brake.