Mechanics and Fixing Any Questions Answered

It's a chamfer ring which sits on top of the top bearing cap.

I'll use lots of GT85 on it then hot water, push down the steerer with a handle bar attached to a stem and it sh should come off.

Resist the urge to hammer the steerer even with a sacrificial top cap, it might deform the top of the steerer and makes the headset removal even more difficult.

Maybe the rust has increased the diameter of the steerer enough to stop the headset ring from sliding back up it. One thing that really eats rust is lemon juice. Fresh from a lemon is best.

So I'd get a cloth and try to remove what rust you can with normal degreaser/cleaner. You can also rub with an old knife, but be careful you don't remove steel. Then wipe it clean/dry, squeeze a lemon onto the steerer, let it sit for a minute. Squeeze another lemon over some wire wool and scrub the very lowest visible section of steerer. Tickle surface with old knife again to see what comes off, final scrub with wire wool, wipe clean, apply GT85 or WD40, attempt wooden block again.

That steerer is crusty af. I’d be straight on that with some fairly coarse emery paper, fuck all this tickling it with lemon juice.

You should be able to give it a fair old doink with a hammer without misshaping the top of the steerer too and with the nick of it, it’ll need it. If you have some files to knock back any distortion then be a bit more gung-ho with the hammer, if not then a bit of wood will do a decent job of protecting it. Rubber mallet could work but you do need to give it a good old shock to get it moving.