So I just got my bike back from the LBS after getting a brand new headset installed. The mechanic says the stack height was a bit too tall and with the lock washer I only had about 3 threads of engagement on the locknut. So he finished the job without the lock washer, having the lock nut sit directly on top of the upper race. He says it will be fine, but I have my doubts. Any of you guys have experience with leaving the lock washer off of a threaded headset? Thanks

You got hosed.
The purpose of the lock washer is to lock into the lock nut. Without the lock washer
your headset is barely tight. It's tight, but not really locked in. When the locking nut and lock washer are used in tandom, it's a solid system, with perfect bearing race tension. You need a different fork.
I would be careful and check the adjustment frequently.

I had this trouble earlier this year:

https://www.bikeforums.net/bicycle-mechanics/81310-threaded-headset-issue.html

It's a long while since I worked on a threaded headset but isn't the point of the washer to make adjustment easier?
There is a grove running the length of the fork and a key on the washer that fits into the grove. This prevents the washer from rotating when you tighten the lock nut. Without the washer the locknut will tighten directly against the race and rotate it during tightening.
With out the washer it is just harder to get the correct ammount of bearing preload.

Washers do more than just make adjustment easier!! A locknut loosen itself from the adjustable cone of the headset over time, due to fretting. From this brief wikipedia article on washers:

"High quality capscrews require hardened steel washers to prevent the loss of pre-load after the torque is applied (due to Brinelling)."

And from the article on Brinelling:

"Brinelling refers to surface fatigue caused by repeated impact or overloading. It is a common cause of roller bearing failures, and loss of preload in bolted joints when a hardened washer is not used. "

That's just bull. I'm sorry. You're better off without the lock washer since if you do have that threaded pos, you'll have to simultaneously adjust three things at once to get the desired HS adjustment in properly.

OP: Your mechanic is fine. He knows what he's doing.

See my above post: a lockwasher DOES serve to hold the preload of the threaded headset (or of any two threaded fasteners which are tightened against each other and subjected to frequent shocks).

It's POSSIBLE to use a threaded headset without a lockwasher, but I would say it's inadvisable. I've done this myself, and the headset became too loose after a few weeks' use.

That's nonsense and rubbish.I run HS with no washer and no issues.

Neer had the problem with any of mine. FWIW, there are locking locknuts.

What was wrong with your original headset?
The lock washer is supposed to prevent the top race from moving when final pressure is applyed TO THE LOCK NUT.The lock washer has a key which prevents it from moving. In my original post, i was referring to headsets that have a threaded lockring with spanner notches under the lock nut. Yes, i agree with Sydney, that it's possible to tighten the lock nut down to the top race, but the final adjustment would be alot more subject to mulitiple random attempts at getting it perfect. As stated earlier, i would be careful and check the adjustment frequently.

Morons cut steerer for specific HS.Use a different HS and often come up a bit short like the original poster. No big mystery.Even with threaded,I cut mine to use an additional 5mm spacer.saves lots of potential later headaches.

All it takes is 2 wrenches.

That's good advice to add 5mm and use a spacer,because, as they say "you can always shorten the steerer but you can't put it back." doe's indeed save a
lot of head aches.

More bull. Do everyone a favour and stop posting your "guesses".

What a bizarre thread!

First of all, it shouldn't even be called a lock washer because that's not what it does. A lock washer is usually splined or split and it is intended to keep a single nut from loosening.

This is more of a spacer. Some are tabbed in an attempt to make the adjusting process easier, but the real action is the two nuts tightening against each other, and you don't need a washer for that.

The bearing pre-load is a function of how tightly the upper race nut is adjusted before the lock nut is cinched into it. As long as the two are tightened properly the preload will not change.

Exactly. The washer in question is not a lock washer. It is an indexed washer. It is there to keep the nut from exerting turning force on the race as the nut is tightened. Lock washers must be serrated or deformed in some way to create additional friction or tension between two surfaces. A smooth headset washer does neither.

SS

I've regularly installed headsets without the washer for that exact reason.....and have never, ever run into ANY problems, whatsoever. I don't think it really serves any practical purpose. That notch on the washer supposedly prevents the lower race from turning when tighening the upper locknut but I always find myself using 2 wrenches, regardless.

It's probably intended for that, but if you don't use 2 wrenches the first thing that happens is the tab strips right off the washer.

I also don't like having a notch cut into the steering tube...

Good catch. And some steerers aren't even notched for the tab.

... so you have to grind the damn thing out or get another washer.

ok, thanks for the responses...it seems that more people say it doesn't matter. So if something does happen, I'll be hunting you all down.j/k Thanks =)

continuing discussion....

So, Chris King co. tells me that their 2nut (their "traditional" threaded headset) does not include a washer for use between the locknut and the upper race. I interpret this statement as "a washer is not necessary for threaded headsets."

afterall, if the best headset in the world does not use a washer and has the locknut sitting directly on top of the race, why would a lesser headset that uses the same basic design have an issue when run without a washer? Thoughts?

This is pretty much a question to people who were telling me that I NEED the washer, and of course to anyone who has information to add to the discussion =) Thanks.

From a generically technical (i.e., not bicycle specific) point of view, the "tab" and "notch" are actually called the "key" and the "keyway," respectively.

Pretty fancy terminology for essentially useless features.

The HS with no washer I buy, but the no issues part...