2 wheeler

I've have had an issue with the threaded headset on a mid 80's Specialized Stumpjumper that I would like some help on. This bike was made prior to suspension forks, so it's a rigid front end.

I had an alloy headset on the bike and an alloy cable stop held by the headset nut. I couldn't keep the nut tight; on every very bumpy ride off road, the nut would loosen. (When I say bumpy, I'm referring to trails that are mainly chunky broken rock that makes your arms tingle from the shaking.) Finally, the nut stripped when I was riding.

Figuring that the alloy cable stop was not allowing enough nut thread engagement, I switched the front brake from cantilever to a linear pull (V) brake; this eliminated the alloy cable hanger. I did this change when I changed out the headset for a really old, but new in the box, Shimano 600EX. On the first ride after installing the new headset, it was the same loose nut problem.

When I installed the new headset and got it adjusted, I noticed that if I turned the fork 180*, it would go from just right to very tight in the bearings. The fixed cups are installed fully and square with the frame, so that's not an issue. I'm wondering if the head tube surfaces aren't square or if the fork steerer tube is bent.

Any ideas what is causing this problem?

Andrew R Stewart 

I think you might have a few issues. The original loosening could be damaged threads. Yes, the alloy top nut is the first threaded item to show damage but the steerer threads or the threaded cone/race could also be damaged. This issue was common before the threadless headset came on the market. many attempts to keep the headset as adjusted developed (set screwed top nuts, nylon locking inserts, LockTite). Once a headset is ridden loose for any period the thread damage can happen and things might never stay tight again. Given the current lack of options in threaded headsets (that I know of) I would try low strength LockTite next. The issue of the actual adjustment with the new head set could be a few things. bent steerer, improperly seated cups or crown race, improper bearings or their installation, seals not installed right. I would start with the basics and make sure that all pressed on parts are actually properly seated (ovalized head tube ends can cock a cup), if any one of the bearing surfaces is not flat with the rest your loose/tight results will happen. make sure the bearings are the right ones and installed correctly (not upside down). Try assembling w/out any seals to eliminate their contribution. Take a straight edge to the fork steerer to check for any bends, pay attention to where the threads are as the steerer can stretch/bend at the threads. The reasons that a headset is loose/tight is more often the fork then the head tube, but check the HT with a machinist's square. The square's blade should run parallel to the HT when the body is placed at a few different points around the end face. Andy.

JohnDThompson 

If the cup is aluminum, it's unlikely to have damaged the steel steer tube threads. This is a Good Thing, as it's generally easier and less expensive to replace the headset than to replace the fork. There are plenty of threaded headsets still available, e.g. the Tange "Levin," Velo-Orange, etc. Tange even makes a threaded headset with roller bearings in the lower cup for better handling of the thrust loads headsets must take in use. Keep the new headset properly adjusted and the threads will stay intact.

The binding the OP describes is indicative of the cups not being perfectly parallel, either because they are not fully seated or because the head tube needs milling and facing. If you have a cup press, you can try re-seating the cups. If that doesn't help, it's time to take it to the LBS for milling and facing.

spinbackle

I have an '87 Stumpjumper Comp that came stock with a Specialized headset. The fork was rigid and threaded. I started having problems with the headset loosening about a year after I got the bike. I would crank down tight on the headset at home and it would eventually loosen itself during the ride (always offroad). I went so far as getting a fanny pack I could keep two Park headset/pedal wrenches with me to tighten things up midride. I eventually was able to get some shorter wrenches but it was a pain to have to stop and tighten things up. I figured this was the way things worked in the universe and accepted this. Then I discovered the Chris King Grip-Nut headset. Yes, it is insanely expensive. I put it on and the rest is as they say, history. Nary a loose headset in the last 7-8 years or so. I was so impressed that now I won't go with anything less than a CK headset on any of my bikes...yes I'm a snob in that regard but have yet to have any headset issues. YMMV.

Andrew R Stewart 

John- All you say is true in my experience. BUT... (there's always a butt) If the HS does loosen and the threaded top cone/cup is steel then the steerer is at risk of thread damage. Which is harder/ the steerer or the bearing piece? There were a number of Japanese HSs with a mix of alloy top nuts and steel top cups/cones.

Also WRT the roller element HSs. I've used StrongLite A9s for many years (just finished a 4 day tour with one) and they are even more sensitive to frame prep and HS installation (as you already know), if there is a frame/fork issue that places the HS parts off parallel then the loose/tight problem just worsens. I'll add that they are susceptible to notching when ridden loose, their conical steel rolling surfaces are (I suspect) made of soft steel. The attempt to get a freely rotating HS adjustment can often result in a loose HS, given their greater rolling friction (compared to a balled HS). Once again an "improvement" can result in a shifting problem.

Always cynical until proved otherwise, Andy.

cyccommute 

Yours is a well known issue to any old mountain biker out there. I've replaced dozens of the damned things and loath them for just this reason. The threads just aren't up to rigors of off-road pounding. In the mid 80s to the mid 90s, loosening headset even sparked a cottage industry of locking mechanism to keep it from happening. Theadless solved the problem completely and elegantly.

You can still find some of the headset locks around. Cambria has some and there are others around. You could also swap to a threadless set but you'd need a 1" fork, a 1" threadless headset, and a 1" threadless stem. Not all of them...the stem in particular...are easy to find nor would the conversion be cheap. I'd start with the thread locking mechanisms.

fietsbob

perhaps the top nut is bottoming out on the end of the steerer tube , before it's adequately Tight.

And maybe using a steel top nut will get the wrench force tight enough without worrying about stripping the Nut.

You are using a proper headset wrench, on the adjustable cup , right ?

2 wheeler

The nut isn't bottoming out, I've checked that. I do have a vintage Campy top nut that I could use, but I'll try LocTite first.

Are Campy headset wrenches good enough?

That's what I'm using.

2 wheeler

I have suspected that it was a design deficiency, since the advent of threadless came after the threaded headset issues became so obvious back in the day.

It really boils down to relegating the bike to road use and picking up a more modern mountain bike. A nearly 30 year old mountain bike (with a nicely dented top tube) isn't worth putting much money into.

JohnDThompson 

Have you inspected the threads on the threaded cup and steer tube to be sure that they're intact? Locktit-ing the top nut is unlikely to accomplish much if those threads are damaged.

2 wheeler

The headset is new and the steerer tube threads are undamaged.

Thanks for your input!

Kimmo

I think you're correct to be wondering about that.

Myosmith

I had the same problem, but simple fix with regular medium strength Lock Tite. Did it to both of my old Trek 700 forks and haven't had a loosening problem since, including on the gravel grinder which takes a lot of vibration.

Grand Bois

It's interesting that you would say that. I've read and always believed that a big advantage of the A-9 is that the floating races make them less sensitive to frame prep and installation. I installed all four of mine with no frame prep and without a proper press. I guess I've just been lucky.

JohnDThompson 

That's been my experience as well. It's the fancy-pants tapered roller bearing units that tend to be exceptionally fussy about alignment.

fietsbob

the A9 bearing retainer edge, just wears the aluminum part that is inserted in the frame , then..