Changed stem by the book - headset loose

[Harleyboy]

Hi, bought a used bike recently with an aggressive stem. Changed for the same brand but longer and smaller angle but having swapped them, the headset is loose. I have torqued to correct level having done the top bolt before the side bolts on stem which I think is the right order. In fact I did the same process only a week ago when I switched the stem round to raise the bars and everything was fine and tight. The only difference this time is that I did it on a stand so was wondering if my forks could have moved and somehow affected things. Nothing obviously visible though and they didn’t fall out! I’m stuck and now have the stem I want but headset play!

What have I missed?

[shouldbworking]

Re adjust the headset with the bike on the ground

[Harleyboy]

Yes, did that to make it easier to line the wheel up straight and even tried the old stem again and that is also loose...have watched many you tube videos and seem to have dine everything right.

[InitialDave]

Is your new stem slightly lower on the steerer tube, causing the top cap to bottom out on the steerer before taking up the slack in the headset?

Try again with an additional headset spacer (above or below the stem would be fine).

[CoupeKid]

I had the same problem.

What I had done was to fit and torque up the stem then add the top cap thinking it was cosmetic.

When I refitted, screwing the top cap up first, then torquing the stem it was absolutely fine.

[Harleyboy]

The stem has the same dimensions and I have used the same two spacers. The top cap was tightened first to preload the bearings before tightening the stem bolts on the side. I don't have any tube left to add another spacer. With
Both spacers it is flush with top of steerer tube.
Have tried one above and one below and just one below although haven’t tried both below yet but can’t see how that would make a difference.

[InitialDave]

It shouldn't be flush to the top of the steerer, the steerer should be a couple of mm below the top of the assembly.

[The_Jackal]

This.
The top cap should not contact the steerer tube at all, in order to actually pull everything together.

[Harleyboy]

Ok, that’s good to know but it was with the old stem and was fine. Will need some different size spacers I think

[Harleyboy]

I knew that old MTB would come in useful someday! It had some varying size spacers and now all is good. Thanks so much for the solution - PH at its finest.

[GOATever]

Tolerances. They’re a nightmare. I’ve never been able to replace headset bits, and had it all go back together, and tension it all up, without having to jig spacers around. I keep a load of spacers, and spare compression rings in my toolkit just in case.

[Gareth79]

Another thing to note - with carbon steerers it's a good idea to have a small spacer above the stem, so that the stem isn't compressing the very top of the tube.

[GOATever]

Gareth79 said:

Another thing to note - with carbon steerers it's a good idea to have a small spacer above the stem, so that the stem isn't compressing the very top of the tube.

And remember that Carbon steerers should have an expander plug as an anchor point, rather than a star nut, so make sure the plug is torqued up properly ( usually 6 - 8 Nm ) or it might shift as you try to tension the headset.

[Harleyboy]

On a positive, the new stem is so much better!

[GOATever]

Harleyboy said:

On a positive, the new stem is so much better!

Good stuff