Tricky Threadless Headset Adjustment
 

I've been working on the install of an integrated threadless headset on a carbon fork w/carbon steerer tube. The headset came with the fork; seems to be the right size because it fits nicely into the integrated races. Crown race, compression ring are seated properly & I've left a gap betw. spacers & the top cap. This is not the first headset I've installed so I know it's not very difficult.

However, try as I might, I cannot get the play completely out of the headset. It seems that the plug is not able to tighten up the compression enough to eliminate play.

Does anyone have any suggestions? Is it possible that carbon spacers or my stem is binding up the steerer tube so that the plug/cap can't work to compress?

First ascertain that you have enough spacers. If there's any question, stack another spacer 3mm/5mm will probably be enough.

The other thing to eliminate is the fact that the compression plug part of your compression plug may be pulling up as you tighten the headset cap.

1) Tell us which one it is
2) Use carbon assembly paste inside the steerer to increase friction
3) Use a higher torque on the 'starnut'

I have enough spacers; seems to be at least 3 mm. I can't tell if the plug is pulling up but I'll try to increase the friction inside the steerer. I'm also thinking that perhaps the top cap is contacting the top of the headtube before fully engaging the compression ring/bearing assembly, since the whole thing (stem, spacers, top cap) needs to be able to slide down onto the compression ring & bearing assembly to firm up the connection. BTW, it's a neco headset - no frills, standard 1 1/8".

Sometimes the split centering cone drops low enough into the bearing top race that the spacers beach out against the race itself rather than the cone. Remove everything and see that the first spacer can press the cone tight without touching the race.

If that is the problem, look for a smaller spacer or shim with an OD equal to the cone so it can be pressed deeper. Alternatively you could wrap the fork at the height of the centering cone to build it up a bit so the cone cinches while still higher.

If it isn't centering cone related, check the bearing orientation, that upper and lower are correct (if not identical) and all spacers so that both upper and lower headset bearings ride on the balls, not on any seal or other obstruction.

But the spacers contact the top cab and not the split centering cone...so I'm not sure what you mean by spacers pressing against the cone (I assume you mean the split compression ring that fits inside the bearing top race). It appears that the top cap has some leeway to press down on the compression ring. If I understand your suggestion correctly, wrapping the steerer underneath the cone (ring) would help it press more firmly against the inside of the upper bearing race. BTW, The bearing races for upper/lower are the same size. It doesn't seem to be an issue with the top plug "slipping" inside the steerer tube as it is tightened.

I think the bearing assemblies are oriented correctly looking at how they fit into the headtube. Any other orientation seems to be a poor fit.

I wonder if it's possible that the headtube races are poorly constructed, thereby allowing some play. I have noticed that there seems to be more than usual side to side flex in the entire handlebar/headset/fork cockpit area.

Thanks for the suggestions, they've been very helpful...keep them coming!

Top edge of stem needs to be proud , above the end of the steerer tube,

if not, add a spacer under the top cap, above the stem.

perhaps the frame's Prep machining was not such that the bearing
sits even all the way around ?

blind guess obviously ..

The way the headset tightens is the split centering cone is pushes the top bearing down shrinks into into is until it's wedged between the bearing and steerer forming a tight press fit. Headsets vary somewhat but the principle is the same. If whatever presses on the cone bottoms against anything other than the cone, you won't get a solid fit between the steerer and bearing.

Building up the steerer diameter a bit raises the height at which the cone jams and solves the problem (if that's what it is). The problem can also be solved with a spacer with an OD small enough to press the cone without touching on the OD.

Seems like the top plug is unable to tighten the whole HS assembly. No problem apparent with the centering cone (tight fit to the steerer & seems to press inside the bearing fine - have enough spacers). The spacers are still loose even after tightening the plug. I'm beginning to think that there's something fundamentally wrong with the HS. Maybe with the crown race - possibly defective (though it is seated completely on the crown).

If the spacers are loose, there's no way that you're compressing them to establish preload. The system is pretty straight forward. the top cap bolt pulls up on the star nut or expander, and pushed the cap down, which in turn pushes the stem and spacer stack down onto the centering cone securing the headset against the steerer and compressing it to get preload.

As a result the spacer stack is under the same amount of compression as the headset bearing, so slack spacers means slack headset. Find out why you cannot compress the spacer stack. reasons include, in order of commonality

1- stem tight and won't slide down freely --- loosen stem bolts
2- top cap beaching on top of steerer rather them top of stack --- add spacers
3- expander plug sliding up and not serving as a fulcrum for the screw --- tighten plug, and or add traction compound to the plug
4- top cap running out of thread and not able to screw in far enough to compress stack --- shorter screw, or push plug in deeper
5- undersized spacer in the stack binding and not sliding freely --- replace or deburr spacer as needed, identify as one with tight spacers above and loose spacers below.

From your description of prior efforts, I'm leaning to #4, but do a complete review. You're missing something obvious, and I doubt it's a headset problem. If the spacer stack is tight and the headset loose, than it might be headset related, inverted bearing, missing internal spacer, etc.

Thanks, FB. Great list to check. Here's where I'm at:

1 - check, everything is (reasonably) loose. With the carbon, seems to be a little more friction than with an AL steerer, but I've tried with some grease to make sure everything can slide freely.
2 - check, have at least 3 mm space at top, maybe more like 5 mm.
3 - check, added friction compound, plug seems nice & tight & can't perceive any slippage.
4 - hmmm...interesting thought. I'll have to take a closer look at this suggestion. I'll try a longer bolt.
5 - check, the spacers don't seem to be an issue, as I've switched them out for clean, AL ones for testing purposes. Though some of the carbon spacers I have don't seem to be completely flat.

The loose stack problem makes me wonder as well, wish the problem was a little more obvious... My perception is that there is minimal play at the crown when I press the fork upwards, but it's really hard to tell.

If the top cap bolt is running out of threads, you need either a shorter bolt or a bolt that is threaded further up the shank.

If the top cap bolt is running out of thread, you don't want a longer one, but a shorter one, or push the plug deeper for the same result. You can easily test the length of the top cap screw.

Remove enough spacers so the steerer sticks out. See if you can tighten the top cap bolt until the top cap touches the steerer. If so you know for sure it can press down on spacers 3-5mm higher than that.

While you're at it tighten the top cap bolt with the cap beached on the top of the steerer (no spacers). The bolt should tighten hard as it bottoms out, if you can continue to turn it, it'll draw the expander up, which may be the problem. Tighten the expander by degrees trial and error until you cannot draw it it up except by torquing beyond what you expect to need to set the headset preload.

I doubt it's the crown race, but it should have needed a bit of force to press on. If it did it's OK and there's no need to check again.

:popcorn You loosening the stem pinch bolts 1st?
and anything you may have clamped onto the steerer.

[mine: 2 stems + a 'locking spacer', right above the top headset race.]

Somebody said this? Check out the compressor inside of the steering tube. It might not be the right size and gets lose.

Tried but no-go for those suggestions...time for a visit to my LBS. I think there's a poor crown race/bearing connection.

Are you absolutely you have the correct headset for your headtube? I ask because you said you go the headset with the fork. The headset specs/type are based on the head tube, not the fork. Maybe let us know what the frame and the headset (i.e. p/n) are.

To me there can be only three reasons for what's happening to you: not enough gap between top cap and upper spacer or stem (you said that wasn't it); the expansion plug is slipping inside the steer tube (my primary guess); or there's some sort of bearing mis match.

Cheers to my LBS! After countless hours of tinkering, tightening, loosening, etc. I couldn't get the HS tightened. Took it down to the LBS, mechanic loosened then tightened and within 30 sec. voila! it was fixed. What did he do differently? Absolutely nothing...but I'm convinced that there's magic in a pro mechanics fingers!

Something to keep in mind for all us amateurs.

Obviously he did something differently. Were you not able to determine what you were doing wrong?

DIY fail : (

I watched as the mechanic simply unbolted the stem, took out the plug, put the plug back in & tightened. But I had ridden the bike the day before & I think the races were able to "self-adjust". Maybe there was some clear coat on the races that needed to wear off. At least that's my best guess.

Maybe paint a bit of a drip, in the frame, where the bearing races sat..