I've tried the plastic tubing/hammer combo and heating it up in boiling water but to no avail. Any other bright ideas people can suggest?

thanks

bigger hammer

I concur. And hit it harder.

Plasic pipe flexes a fair bit. It's amazing how hard you have to hit it. Like, as hard as you possibly can!

or cut a slot in it with a hacksaw.

i use a screwdriver and lump hammer, make sure i hit the bits where the bearings dont sit! the closer to the inner diameter/steerer tube the better, just do it slowly, bit by bit, working round the diamter a couple of times.

Del – that only works if it's a cartridge bearing unit, it it's balls or rollers, that will index the headset each time a ball/roller drops into the gap

I had to resort to resting the underside of the crown on a piece of well padded wood so the legs/internals wouldnt take any of the impact. And it went on in one hit.

cp – of course this is true, but didn't think anyone would be fitting one of those sorts of h/seats to an mtb. 😉

Don't know if this will work with crowns but I have stuck my headset cups in the freezer after another persons advice and they went in the frame so much easier once chilled.

It's not the crown race's problem, it's the crown on the fork. This should be prepped using a cutting tool to ensure it's the correct diameter and the crown race seat is square. You'll bugger the headset and the bearings and potentially the fork if you just whump it on.