New build and new headset – is it just the cups and crown race settling into position – only takes a few thou of achievement to create play

In fact the more I think about it…

are you absolutely sure you havent put the compression ring above the cover?
It is supposed to centralise the steerer in the bearings i.e. contact steerer and top bearing inner race. The cover itself is a “loose” fit just to keep the crap off the top of the bearings and sits over the compression ring and the top bearing.

As TJ says check the steerer isn’t pulling through, I’ve seen someone with some fairly nasty injuries where some mechanic thought it would be a good idea to fit a steerer tube without a lower retaining lip to some Marzocchis.

As Brant states stems can creep without the top cap fitted, not common though.

The compression ring on THE PIG is on the top it has no cover like the Orbit, The spacer washers fit straight on top of the compression washer.
What clearance do you guys allow between the top of the steerer tube and the top of the spacer washer for the cap to preload the headset?

What clearance do you guys allow between the top of the steerer tube and the top of the spacer washer for the cap to preload the headset?

however much is neccessary for no part of the cap to bed down on the steere tube. IMO at least 4mm, usually 5mm

I wonder if the top cap is being deformed when its nipped and pulling down and touching the steerer tube. I normally measure the clearance and try to leave 2 to 3mm plus. Maybe with this type of headset/cap I need a bit more. I will play around with the spacers and report back.

Thanks for all your suggestions and help!

Try it with a larger spacer above the stem (giving more steerer clearance) and see if the problem persists.

Are you 100% sure the races are in the right way up/correct for top and bottom? With cartridges you probably can’t do it wrong but I contrived to fit one race the wrong way round on a WTB greaseguard headset and had exactly the same symptoms as you describe.

im going with headset, if you use spacers under the stem make sure they are pushing the ( sorry for the grammer i did see the diagram but didnt pay attention), wedge shaped, usually plastic part.
i had the same problem in the end the spacers were pushing the top bearing cover not the wedge and therefore blah blah stem comes loose bong.

Will try it with 4 to 5mm like Stoner suggests and try it tomorrow night, see if I have any joy! There is no top cover on this type of headset, the spacers sit on the compression washer. The bottom race on The PIG is huge so can’t mix up. It’s meant for bmx and downhill so its quite strong. 😕

put a threaded 6mm bar through as a headloc.
never loose again.

I have 2 456 stems fitted to 2…456’s!!
Both with FSA headsets and neither has ever shown the slightest inclination to budge. The steel 456 has been built up since 2005 and had almost no maintenance done at all.
Having said that I can’t think of a single stem that has worked loose on any of the 10 bikes I have 😳
I am slightly well built & tighten bolts for a living so that might have some bearing on the matter 😉