Bicycle Mechanics - Fore/aft play in headset

Completing my very first build has been frustratingly delayed by a loose headset that I cannot fix. After reading a number of posts, both on BF and elsewhere on the interwebs, it seems that I've assembled the headset, expander plug, stem, and top cap correctly. However, just to be sure, and before I swallow my neophyte pride and take it to my LBS I'm asking those with experience troubleshooting loose headsets for help.

Pics show the type of expander plug, top cap and stem. I am using the expander plug for preload prior to tightening the bolts on the stem and tightening the top cap. Top cap does not contact the steerer tube.However the design of the expander plug requires that it sit on top of the steerer tube.

When firmly tightened, there's fore/ aft play that shouldn't be present.

More info:

I took everything apart just to be doubly sure that the drop-in angular contact bearings are installed correctly along with the centering ring. The fork crown race was installed by LBS.

The top cap is a spare given to me by the LBS after I purchased one that clearly was not designed for the type expander plug that I have.

Extra steerer exists until I get fit dialed in. Tube is tapered 1 1/8" to 1 1/2".

http://www.cultureandlanguage.org/Images/plug1.jpg
http://www.cultureandlanguage.org/Images/plug2.jpg
http://www.cultureandlanguage.org/Images/plug3.jpg
http://www.cultureandlanguage.org/Images/plug4.jpg
http://www.cultureandlanguage.org/Images/plug5.jpg
http://www.cultureandlanguage.org/Images/plug7.jpg
http://www.cultureandlanguage.org/Images/plug8.jpg
http://www.cultureandlanguage.org/Images/cap1.jpg

Any suggestions? Thanks in advance.

are the bolts that clamp the stem to the steerer loose while you are adjusting the bearing preload? they need to be.

also, the topcap mgiht be sitting on the expander plug after snugging up to the top spacer. have you tried adding another spacer to the top?

Yes, the stem bolts are loose when adjusting bearing preload. I will add another spacer to elevate the top cap some and see if that helps. How tight should the expander plug be prior to tightening the top cap? Or asked another way, how much should should tightening the top cap also tighten the expander plug? Thanks.

Are you sure the top cap is not touching the steerer tube when installed and setting the preload?

Some top caps have a curve to them towards the center which usually does not present a problem when using an expander plug that sets inside the steerer or with an aluminum steerer with a starfangled nut.

If your top cap has such a curve then there might not be enough clearance to set your preload since your expander plug sits on top of the steerer.

-j

Yes, make sure the stem is loose and the expander plug tight before adjusting the top cap bolt to preload the headest.

If the stem is tightened you can't push it down, and if the expander plug is loose you'll draw it up instead of bringing the top cap and stack down.

Also, should have said this first, make sure the split centering cone is in place, and the spacers are pressing on it and not on the top bearing of the headset.

Tightening the topcap/preload bolt does not tighten the expander plug. If there is no manufacturer torque spec, then the expander plug should be just tight enough that it does not slip when adjusting the preload.

-j

FB...need to edit your post....replace "and if the top cap is loose you'll draw it up instead of bringing the top cap and stack down." with "and if the expander plug is loose...."


-j

Are you sure the top cap is not touching the steerer tube when installed and setting the preload?

Some top caps have a curve to them towards the center which usually does not present a problem when using an expander plug that sets inside the steerer or with an aluminum steerer with a starfangled nut.

If your top cap has such a curve then there might not be enough clearance to set your preload since your expander plug sits on top of the steerer.

-j

Thanks for your help. I will add another spacer as time bandit suggested just to be sure. However, as you note the design of the expander plug results in the lip of the plug sitting on tip of the steerer tube. Would the top cap touching the top of the expander plug be equivalent to making contact with the steerer?

Absolutely.

The recommended gap between top of stem (or the top of uppermost spacer) and the top of the steerer (or the top of an expander plug sitting on top of the steerer) is 3mm.

-j

You do 100% of the preloading with the top cap bolt, the stem bolts need to be loose while you do this, and the expander plug bolt needs to be completely tight before you do it. It seems unclear at this point if you realize this. You will tighten the top cap bolt enough to take all the play out of the headset and not so tight that it binds the steering in any way. This is the correct preload adjustment. Once this is done you tighten the stem bolts.

FB...need to edit your post....replace "and if the top cap is loose you'll draw it up instead of bringing the top cap and stack down." with "and if the expander plug is loose...."


-j

Thanks, fixed.

BTW- If you did all the basics - tight expander that doesn't slip, and loose stem - take a minute to take everything off down to the split expander cone and the first spacer. Press the spacer down and make sure it always touches only the expander cone, and doesn't bottom out on the bearing top cap. In some headsets you need a small OD washer on top of the cone before the rest of the stack.

You do 100% of the preloading with the top cap bolt, the stem bolts need to be loose while you do this, and the expander plug bolt needs to be completely tight before you do it. It seems unclear at this point if you realize this. You will tighten the top cap bolt enough to take all the play out of the headset and not so tight that it binds the steering in any way. This is the correct preload adjustment. Once this is done you tighten the stem bolts.

Yes, you're assessment of me is correct. I suppose that I'm unsure as to the interaction between tightening the expander plug vs. the top cap. Haven't had a chance to look at it tonight. Will follow your and the others suggestions as soon as I'm able. Thanks.

BTW- If you did all the basics - tight expander that doesn't slip, and loose stem - take a minute to take everything off down to the split expander cone and the first spacer. Press the spacer down and make sure it always touches only the expander cone, and doesn't bottom out on the bearing top cap. In some headsets you need a small OD washer on top of the cone before the rest of the stack.

This is the same as the centering ring, right? And yes, I have the small washer on top of this split ring as you describe.

You guys are awesome. Sure enough, tightening the expander so that it would not slip, adding the extra spacer, and tightening the top cap did the trick! Thank you all.