Help Solve This Stem/Headset Puzzler
 

I was doing my twice year removal and re-greasing of seat post, stem and fork steerer tube so that they won't get stuck.

I put the fork back in and tightened the head set with the stem cap bolt, doing the tests to make sure it is tight, but not too tight. (I have been doing my own bike builds for years and was a shop mechanic for a time.) Then I tightened the stem bolts to 5 nm and did the test again, but I could feel a slight looseness, or movement thru the handle bars. Testing the headset by engaging the front brake was solid and there is no play in the fork stanchions and it is not overly tight. I loosened the stem bolts and the feel of looseness and movement were gone. Then I re-tightened the stem bolts and it was back. I tried a different stem with the same results; headset tightened correctly with the stem cap bolt and all is fine, tighten the stem bolts and the slight looseness, or movement thru the handle bars is back. (I checked and reinstalled the headset and it is fine and it is relatively new.)

Any ideas?

Did you inspect the steerer tube? Any chance it's cracked?

it's possible, i guess, that the stem clamp is defective in some way. out of round? bent?, etc. permitting play when tightened. i'd try a stem that i knew was OK, and see where that leads you.

It will be done after work, dang, I should have thought of that, but I do hope that is not it.

Little tip when removing old parts like bearings you plan on reusing keep track of how they were removed and always put them back as they were removed do not swap them around or flip them.
This way any wear that they may have will keep them matched up with each other.
Other than that advice above has already been given good luck with finding the issue.

I was taught this in the air force years ago - clean towel, parts laid out in the order they came off.

Checked everything. My son came into the shop and asked what was up. He took a second look at everything and found a barley visible hairline crack on the stem. The crack was running up from the bottom pinch bolt of a Ritchey WCS stem, and yes, I torque to specs, 5nm in this case with the Ritchey torque tool. Checked it with my Park torque and the wrenches agree, so a bum stem or just wear-and-tear I guess.

Hmm - bad luck - lucky it was just the stem though, and not the frame. ;)

Maybe also check (how?) if the clamp is putting disproportionate pressure on the stem in one area.

I expect it was a casting or forging flaw in the stem. Wear and tear would have to be monumental to crack it. Does Ritchey have a warranty on their parts? Maybe you get a replacement at no cost.

No matter the origins of the defect; good that it was found and part taken out before anyone got hurt.

Be sure to give the Ritchey folks a call or an email ... willing to bet they will get right back to you and want the bad item back for examination. And I would suspect you would be getting a new one back in the mail rather soon also. They are pretty hard core about both quality and customer care...at least to my experience.

I'm not sure the problem has been isolated. Two tested stems yielded the same result. Both cracked?
The original description suggested to me something amiss with the headset.

What Fe said.

Ferrous B. is correct about two stems giving the same effect. The first "control" stem I tried was an old Moto Ace with a rather large stack height and only one pinch bolt was making good contact with the fork steer-er tube. That must be why it had the same feeling of looseness and movement as the stem with the cracks, (closer examination of the cracked stem revealed a hairline crack at the other pinch bolt as well). I have since tried it with a proper 40 mm stack height stem while waiting for my new one to arrive and the headset/stem is adjusted correctly. It would not be right to expect Ritchey to warranty this stem, as I bought it (supposedly slightly used) at a local gear swap and it may have suffered from a heavy-handed install at some point, a drawback for using light-weight used parts. And to think I bombed down some gnarly Pisgah trails with that stem. . . . . whew!
Thanks everyone.

Glad you got it sorted.