Why does threaded headset keep loosening?
 

I replaced a pitted/brinneled headset with a new one recently. All new headset, including lower/upper races and crown race. Tange Levin alloy unit.

• Had the head tube faced by the LBS.
• Used a dedicated headset press (cheap brand but still better than any DIY method) to press in the cups.
• Adjusted the headset to have some preload once the locknut was tightened.
• Locknut is secured by at least 4 threads (i.e., steerer is not cut too short).
• Locknut is not bottomed out (i.e., steerer not cut too long).
• All preload adjustments made with the stem fully tightened in the steerer.
• Headset passed the "no clunking when rocking the bike with the front brake locked" test (i.e., not too little preload).
• Headset passed the "fork rotates smoothly" test (i.e., not too much preload, no binding at any fork position).

The headset continued to feel great for about a month, when I performed the rocking test and felt a little clunk/wobble, so I increased the preload slightly. I figured it took a month for everything to seat and this would be the only adjustment it needs for a long time.

A month later, the same dilemma. A month later, again. Month after month I have to readjust because the preload becomes too loose. I noticed that each time, the locknut is anywhere between finger loose to barely tightened.

I concluded that the locknut keeps coming loose, allowing the top race to loosen. But why? The headset-mounted brake cable stop is keyed so there is no rotation of it between the top race and the locknut. And when I tighten the locknut against the cable stop, it's pretty tight. I can't fathom why it keeps coming loose. The locknut is alloy, in case that makes a difference?

I'm considering applying some locktite to the locknut and see if that helps. Is that a bad idea?

What am I missing here?

Not tightened enough?

+1, get 2 proper headset wrenches ..

Are you sure the top nut is not bottoming out on the end of the fork steerer. ?

how much clearance is left ? [answer with measurements] if so get a thicker spacer..

Are you tightening the top race and lock nut against each other?

my first thought. it can happen, especially when using a keyed brake cable stop to prevent the adjustable cup from turning when tightening the locknut, rather than holding the cup or backing it against the locknut. it's not quite the same thing, IME.

Just a suspicion which you can confirm or rule out.

Swing the bars around, and see if the brake hanger hits the top tube before the handle bar does. If so, that's your problem.

When you handle the bike (not when riding) the front wheel swings around, bumping the hanger. This moves it a few degrees, then moves it back when it bumps in the other direction. The repeated bumping and small back and forth movement arc works the locknut loose.

Pretty sure there is not too much steerer. I tested this.

The keyed cable stop is in between the top race and locknut.

The bars hit the top tube before the cable stop does. I also don't allow my bars to swing all the way like that when I'm handling the bike.

OK, so it's not the hanger getting knocked around, so we're back to the original and basic question of are you tightening it properly. More specifically are you using two wrenches, one for the upper bearing, and one for the locknut? If not, then it's simply a case of night tight enough.

from the first post, it sounds to me like the OP is trusting the keyed cable hanger to keep the adjustable cup from turning when tightening the locknut. and is NOT holding the cup with anything at all. and assumes that just tightening the locknut onto the keyed cable hanger will be sufficient. as i mentioned, i'm not so sure it is.

i have done this in the past with a keyed washer instead of a cable hanger and was disappointed with the results.

a pic would be nice.

had the keyed washer turn and just take the threads out of the fork, before, when the lock nut was being tightened..

OP ignored the critical questions -- so typical of this forum.

I think we can deduce the answers.

+1 this. It may simply need a spacer under the locknut to prevent the shoulder on the locknut from bottoming out on the end of the steer tube. Failing that, check the threads on the aluminum locknut and threaded cup. They can get damaged easiy by the harder steel steer tube if they are ridden while loose. Eroded threads on the steer tube itself are another possibility, but this damage would have happened earlier, if a steel headset was used before the current one.

Ive substituted a steel locknut for an Aluminum one , before ..

I particularly liked the one Tange Made, which has an O ring in it to go around the stem to better keep water out .

Couldn't OP use a marker to put a match-mark on the locknut, adj bearing, and upper cup? Since it takes a month to develop looseness he should be able to monitor it.

scott s.
.

Jeesh. Somebody's cranky. If you go back and read my original post, you should be able to pick up on the fact that I included more pertinent info than 99.999% of the people posting about problems they're having.

One interesting thing that I take from this thread is that YOU, [MENTION=331655]AnkleWork[/MENTION], are the only one who has replied without actually contributed anything meaningful to the discussion -- so typical of a troll.

I don't have two headset wrenches, but I used the headset wrench on the top cup while tightening the locknut with channel-lock pliers. Here's a pic of the bike, and a pic of the headset:

https://farm8.staticflickr.com/7439/...e62cf391_h.jpg

https://farm3.staticflickr.com/2808/...47823056_h.jpg

thanks for the pic.

well, if you had a good hold on the top cup flats and cranked down hard on the locknut and you still are having problems, i suppose a little locktite couldn't hurt. i wish you well. :)

+1. I'm a little late in getting back to this thread, but I'd had a similar problem with my '91 Eros a couple years ago after servicing the headset bearings. It also has a keyed washer, but it kept working itself loose until I firmly tightened the lock nut against the top cup (using a large adjustable wrench on the lock nut.) Now that I do that, it holds its adjustment pretty darned well.

Having drooled over just about every bike SPB posted in the C&V, it's pretty evident he knows his stuff. That being said, ditch the channel locks and get a 12" adjustable wrench or a second headset wrench as others have suggested.

Using Loctite ( it should be the blue one ) would not hurt anything so go ahead and use it . One possibly is the treads on the steering tube , are they ok or are they a little mess up do to the key washer or in this case the cable hanger . If this is the problem using a tread chaser (file ) will clean them up . If the treads are off a little they can keep the locknut from tightening all the way . Another trick is use another spacer with the cable hanger .

He's hardwired to be negative and condescending. Never offers a solution, only points out that you, your methods, your posts, or your photos are substandard.

Beautiful bike BTW.

Thanks [MENTION=332136]likebike23[/MENTION]! I know I should use a 2nd dedicated headset wrench, but sometimes one has to improvise. It's on my list!

Check and check on loctite! I'm going to give it a try and report back in a month.

Thanks for all the suggestions! This one has me stumped.

You might be hardwired to perceive things as negative which are actually neutral.

Looks like post #2 was helpful after all. QED.

OK, so I removed the stem, locknut and cable stop and I think I discovered the cause of the problem. Apparently the front of the cable stop, which is cast with reinforcements that protrude downward fore of the section that seats against the top cup, was interfering and not allowing the stop to seat squarely on the top cup. I don't know why I didn't catch this when I initially installed it. Anyway, there isn't enough steerer height to add a headset spacer, which would have solved the problem. Instead, I filed down the interfering points on the cable stop just a millimeter or so which allows it to seat properly. I'll post a pic tomorrow.