quill stem won't stay put!
 

Hi, i have a 1 1/8" quill stem that won't stay put in the steerer tube. I had a problem with the headset not staying tight, so I installed a top lock nut from a different headset (still 1 1/8" threaded) because I had gouged the edges on the original lock nut pretty decently. I got the headset adjusted just fine, but now I can't get the stem to stay in place! It seems to just barely take any allen wrenching to bottom out at max tightness, and then it definitley doesn't stay put when I push on the handlebars.

Any ideas about how I managed to mess this up? I could try the original headset locknut again, but I can't see how this would matter. The stem itself slides down through the lock nut just fine, so wouldn't that eliminate it as a problem source?

Thanks,

TB

I can't see the locknut having any effect. The quill tensions itself against the inside wall of the steerer tube. Perhaps is seems backwards, but have you tired cleaning and some light lubrication on the quill, steerer and wedge assembly? Perhaps something is not able to get tightened enough to hold.

Have you tried a different stem just to see if it holds tight?

7/8" stem in a 1" fork? My old Shogun is 1 1/8 threaded fork with a 7/8 stem,it has an extra thick steerer tube.

Not much to go wrong,threads messed up/rusted on the bolt?

First, what kind of wedge is on the bottom of the stem, is it a slant type wedge or a conical one. I think Slant type wedges grab on to steerer tubes much better than conical style wedges. You might consider switching over to a slant type if you can't make a conical wedge work out for your bike. Make sure the quill wedge isn't hanging up on a dent or a burrs at the bottom of the stem. if it is, you need to file/smoothen it out so that the wedge will have full movement. I also agree that you should thoroughly clean up the steerer tube interior to get rid of any built up grease and just lightly oil the stem before reinstalling it to avoid any future corrosion caused seizures. I really think that sometimes people tend to over lubricate their stems and seatposts which sometimes results in them not being able to make them stay put, no matter how tight they set their clamps or wedges.
Chombi

Thanks for the responses! More detail:

I tried 2 stems, both greased and are slant wedge types. Both slip under medium torsion on the handlebars.

one weird thing is that with both stems it seems like the stem bolt travels only a very little distance before meeting the "tight" setting....which I don't recall in the past. It seems like the bolts used to turn quite a ways under increasing tightness when I would tighten them.

I'll start by cleaning out the steerer tube and stem with a solvent, then just apply light oil....maybe it's over-greased? It that doesn't work, I guess I better look at the fork and determine if it's chipped or bulged or cracked or something.

Maybe the obvious but did you perhaps insert the stems so far that the stem bolt is bottoming out?

Hope it's not some sort of damage to the steering tube that's causing it as you mentioned.
Some wedges also have serrations on them where they contact the steering tube to make them grip on to the steerer tube walls better. You might be able to find those wedge pieces on old used stems in the used parts bins in some bike shops. If that won't work I dunno what else will.

Chombi

Good thought. Have a peek in the steerer tube with a flashlight.

Is the wedge aligned properly to the stem? Having the wedge all the way loose when inserting the stem can do this. If this is the correct diagnosis, tightening the bolt to the point where the wedge can't come out of alignment, but can still slide in the steerer is just the ticket.

Here's another possibility, from Sheldon:

"Steerers are butted at the bottom, so the hole in the steerer is constant-diameter until near the bottom, then the walls taper inward in the butted section.
It is vitally important that the stem extender (or stem) not be inserted so far that the wedge is installed where the steerer is narrowing, or it could come loose unpredictably.

When this happens, only the edge/corner of the quill or wedge contacts the steerer, and it is trying to "grab" a slanted surface."

I once tried to use two different quill stems I had bought from a swap meet and couldnt figure out why they werent tightening enough. I eventually discovered both the stems I had purchased came with mismatched wedges. That is to say, the stems were clearly marked 22.2, but the wedges were slightly narrower, obviously meant for the somewhat obscure 21.1 size. Is it possible that your 25.4 quill stem, which isnt the most common size, has a slightly undersized wedge with it? Maybe one meant for the more common 22.2 size? (If you bought the stem -new- I suppose this possibility isnt possible.)

Problem fixed: I wiped out the steerer tube clean and still couldn't get the stem to hold.....and I again noticed that the bolt had far less travel than I recalled (i.e. very little turning of the allen key was needed to reach max tightness).

I tried looking at the threads of the bolt and added a little grease. Then I added a little grease to under the bolt head...which was rusty and dirty.

Bingo! The tightening felt like normal again and it's in there good now. Thanks!