sheba

I've tried 3 stems, but after a rough ride my headset is always loose.

The bike: brand new Bianchi PUSS, new CKing headset, new rigid steel fork.
The frame and fork were all properly faced. The steerer tube is exactly 1.124 inches in diameter.
Stems tried: Thomson elite, cheap OEM Giant, Thomson 4X elite.

The guys at Thomson said that sometimes steel steerer tubes are so smooth that they recommend roughing them up with some sandpaper. Well, I don't want to grab the sandpaper quite yet.

Has anyone else ever heard of this/ had this happen to them?
What can I do?

AndrewP

Are you sure you have inserted the socket head bolts to tightem the stem, from the correct side (they go in the unthreaded side first and cross the gap at the back to the unthreaded side)? I ask this because somebody on this forum had trouble tightening his stem after he flipped it. He eventually found he had been inserting the bolts in the direction they had been before he flipped the stem.

roadfix

I assume you're preloading the headset properly before cinching the stem bolts tight, correct?

Soil_Sampler

Thomson guys are right!

sheba

Hmmm, are you just saying that or do you actually have some real-world example/ experience?

sheba

And yes, the bolts are inserted correctly.
The headset is properly preloaded before the stem is tightened.

roadfix

I also must assume the upper and lower cups are firmly pressed onto the headtube.

If everything else checks out ok perhaps the stem is slipping on the steerer tube. Do you also notice a little misalignment between the bar/stem and your front wheel when this happens?

sheba

Yeah, everything checks out completely. I've examined all the bearing surfaces for signs of wear or damage as well.
As far as lateral alignment of the stem, the stem always stays aligned with the front wheel.
From all I can tell, the stem is slipping up on the steerer tube.

operator

Time to grab the sandpaper.

CharlesC

I have a question: Threaded headsets have worked perfect for over a hundred years. Where's the need for a non-threaded headset? I don't get it.

operator

Uh, a bit stronger than threaded system and looks uglier + weighs less.

ridelugs

i've had this issue with a king headset and vicious steel fork. problem: king star nuts suck nuts. they make a great headset and a worthless star nut. the top cap would appear tight and then i would ride it, the nut would slip, and the stem couldnt hold on for the ride. get a generic star nut would be my recommendation. sandpaper? lame sauce.

ridelugs

i second that, for everything but freeride and downhill. i ride a nitto stem on all my bikes and its great, if it flexes i cant feel it, and i say that after coming off a vicious cycles with a rigid fork and thomson stem, ect ect...

dalmore

I'm a novice here so realize these are just questions nothing more. Why wouldn't the stem be just as likely to end up off center if it's truly slipping. After all you turn much more than you un-weight the front end. So doesn't the staying on center - but slipping vertically - point more towards improper preload probably due to a malfunctioning/misinstalled star nut or broken spacers? Just curious and trying to learn.

thomson

I am a little confused by this post. The star nut has no role after the stem is tightened.

I have not had the slipping problem but the solution that makes the most sense to me is to rough the surfaces a bit. I would sandpaper the steerer.

freeranger

I'm with thomson on this one. The only purpose of the star nut is to preload the bearings while you tighten the stem. The stem holds the assembly tight (well it is supposed to, but doesn't seem to be working here). Sounds like one slippery steel steerer! Have you checked the steerer to make sure it is not "ovalized"? No reason it should be, but there's no reason one of those stems shouldn't be holding either. (never had this happen-on several fork installations).

ridelugs

hold on, you've never had the problem, i've had the exact problem, and have solved it, and your saying it doesnt make sense? hmmm.

freeranger

The ONLY purpose of the star nut and top cap is to preload the headset bearings before the stem is tightened. And it isn't just me and Thomson--even Sheldon Brown has stated that is the only purpose of a star nut and top cap. If your star nut was slipping and you couldn't preload the headset bearings correctly, then that is another problem, but sheba is saying that things are tight, and that the headset is loose at the end of the ride. Once preload is correct, and the stem is tight, you could remove the top cap and nothing would change. The top cap does not hold the stem tight-the stem bolts do that.

freeranger

sheba, just thought of one more thing for you to check. Is the top of the stem about 3mm above the top of the steerer tube? If not, when you tighten the top cap, it could be tightening against the steerer instead of the stem, in which case you wouldn't be preloading the bearings in the headset. If the steerer is above the top of the stem, you could add a spacer before putting on the top cap, but the headset needs to have adequate preload to function correctly. Also, is the crown race(below the top tube, on the steerer tube, seated correctly. The jarring from riding could be working it down where it should be, which would result in some looseness. Hope you get it figured out and fixed!

Peek the Geek

I hate to ask the obvious, but, are you sure there is no grease on the steerer tube or the inside of the stem? I know excess grease on the bolts of my Elite had a tendency to make it's way in onto the steer tube due to the unique design of that stem. I'm guessing you already know to clean the surface of grease, though, so...

Also, are you alternating between bolts when tightening them down, torqueing each a bit at a time until both are properly tightened. I had a problem similar to yours with my Elite---it would slide up the steerer during rough rides. I was tightening one bolt at a time, which is apparently a no-no with the Elite design. Alternating between bolts solved the problem (though it was a bit of a pain since each bolt was on opposite sides of the Elite---an issue Thomson was smart enough to remedy with the X2 and X4 designs.)

Not sure if any of this'll help, but might be worth consideration.

Sounds like a nice bike, by the way. Is it the pink frame? What gears are you running? And what tires are you using?

ridelugs

ok then. your totally right. my solution didnt work, i was just dreaming that it did. also, everyone takes off thier top caps to save weight, cause you dont ****ing need them once everything is adjusted. oh wait they dont. also, if this were entirely the case, people would never use star nuts but rather expansion nuts, which are removable, to save weight.

roadfix

Correct, the stem cap, the cap bolt, star nut/compression bolt have absolutely no purpose other than to initially preload the headset bearings. After the stem has been secured these items can be thrown out if one wishes to but no one usually does.

sheba

Alright, to answer everyone's questions at once:
Nope, there is no grease on the contacting surfaces.
Yes, there is about 3mm of space between the top of the steerer tube and the stem.
The star nut does not appear to be slipping, but that really shouldn't matter anyway once the stem is tightened down.
Yes, I always alternate between tightening the bolts until they are both very secure.
All bolts have been greased.
The steerer tube is not ovalized.

Thomson has agreed to swap my stem for free and see if that makes any difference.
In the meantime, I trashed that starnut system and put an Azonic headlock on there.
I'll tell you guys how it works out after a ride or two.

Yeah, it's the pink one. Running 32 x 17. Conti Explorer on the back and Vertical on the front. So far, it's the sweetest bike I've ever had, but hey, it's still new.

ridelugs

i wonder why? no wait i dont.

truckin

Well, the reasons I don't pull my topcaps and starnuts are: if I have to adjust the headset later I can do so easily (without having to go find a cap , starnut and bolt); and while not watertight by any means, having the cap in place prevents water or other items from going down the steerer tube. Plus, it's a cleaner look with the top cap on than without it, and I'm not racing at a level where that kind of weight matters.