Play in headset from stem moving

Nick Payne

I recently finished building up a Kinesis ATR V2 frame with the Kinesis ATR fork. About every second or third ride that I take it on, I find that the headset has come loose - I can detect slight play when I lock the front brake and rock the bike forward and back).

The headset is the one that was supplied with the frame (FSA No.42/ACB), I've dropped the forks out and checked that the crown race is properly installed with a crown race setter (it is), the bearing seats are part of the head tube so no cups to press in, so the culprit would seem to be that the stem is gradually working its way up the steerer tube. I loosen the stem bolts, tighten the top cap to remove play, torque the stem bolts again, and check that there is no play, but after a few hours of riding, the play has returned. I use carbon assembly paste between the stem and steerer and the stem bolts are torqued to the 5Nm specified on the stem.

We have seven or eight other bikes in our garage that I've also built up, and this is the only one where this problem is happening. Any suggestions on a fix? I'm reluctant to tighten the bolts past the recommended torque. The stem is a Ritchey WCS - I have the same stem on a couple of other bikes and the headsets on those are not developing play.

The Rookie

Check if it's the headset by putting your finger across the joint when you rock it, it can be play elsewhere.

It can happen if the headset wasn't properly inserted as it works its way in it goes loose.

A properly done up stem will not work loose.

svetty

Sounds like the top bearing cover may be catching the top of the head tube. Try a thin shim on top of the upper bearing split ring under the bearing cover

onionmk

It's unlikely that this is a result of the stem moving up as there's always downward force on the stem from the weight of your hands resting on them.

It may be that the headset assembly isn't seated correctly. So when you tighten the preload it may seem fine, but then when something eventually moves out of place you'll find play. Try putting it back together from bottom to top while keeping everything seated as you go then tighten the preload as much as it will go without 'excessive torque'. That should ensure it's all flush. This worked for my merida where the bearing cover was a tight fit on the steerer. I had to tighten the preload to effectively 'push' the cover down the last mm or so until it seated correctly.

jgsi

Go back a few steps..
Alloy or carbon steerer?
Starnut or bung?
Definitely no to over tightening the stem bolts.... its not there where the fault is.

keef66

Logically if you are able to remove all the play when tightening the top-cap but it reappears after 2 or 3 rides, the stem must be moving up the steerer.

Is it a carbon steerer? Is the part of the stem that's clamped fully supported internally by an expander bung?

Is there still a uniform gap in the stem clamp when it's done up. Are you tightening the bolts alternately and progressively rather than torquing one fully then the other?

The other possibility is that you aren't actually removing all the play, either because there's insufficient clearance beneath the top-cap, or because the bung (or star nut) isn't secure and is being pulled up the steerer.

Nick Payne

Well, after a bit of experimentation, I think the problem was with the carbon assembly paste I was using. I removed the stem from the steerer, cleaned and degreased the mating surfaces on the stem and steerer, and re-assembled to the same torque settings without using anything between the two. It's been two or three weeks since, and I haven't had to loosen the stem and tighten the top cap to to remove play in the headset, whereas before it needed doing every two or three rides.

The carbon paste I was using was Motorex brand. On doing a bit of searching it seems that this doesn't use suspended particles in the grease to provide mechanical friction. as other assembly pastes do, but claims to have some formulation that increases friction under compression. This certainly didn't seem to be doing the job with the components I was using - Ritchey WCS stem on a Kinesis carbon steerer fork.

sungod

i wouldn't use cf assembly paste on a steerer, if it gets washed down into the bearings they'll go gritty

just fit clean and dry as you have done, 5Nm should be plenty