Steering Head Bearings

[moore84rs]

1984 RS
Luftmeister top yoke

San Jose Fork Brace

Steering bearings were replaced 600 miles ago by a local shop. I have never been happy with the
adjustment and noticed a thunk over low speed bumps. To check the adjustment I removed the
fairing, disconnected the damper, removed the calipers. They were notched at the center position.

Bearings have been replaced and I am having a problem adjusting them. It is impossible
to get the fore and aft movement out with the adjusting nut cranked up as tight as it will go.
They feel almost right with top nut torqued to spec., but, It should be possible to get there
with the adjusting nut alone.

Is it possible that the center stem is set high in the lower yoke so the nut is running out of threads
and bottoming out before if creates any preload?

[wirewrkr]

are you saying that the forks are notchy?

[ME 109]

If the top bearing isn't a slide fit on the stem, it can be difficult to determine 'zero' load /play using the adjuster nut.
It should be possible to measure components to see whether there is enough thread or not.

All advice worth < 2 cents.

[Duane Ausherman]

I can't remember the details now, but if the fork tubes are in the wrong position, then the adjustment must bend the plate to tighten down. That top clamp is strong and would resist bending.

Am I mixed up about this set-up?

[moore84rs]

The bearings were notched at the center position. New bearings in now. I am thinking
that they were running loose and got hammered.

Duane, the Luftmiester top clamp is aluminum and clamps the fork tubes, like the stock
lower clamp. I have both loose while adjusting. But unlike the stock steel top clamp with
through holes, the holes are counterbored to receive the fork tubes. I will dig up the stock
top clamp and measure it's thickness and compare it to the thickness minus the counterbore.
It might be creating more clearance between the bottom of the top clamp and the adjuster
nut, so it may need to "bend" the top clamp down to take up the clearance as you suggest.

I think I am wrongly expecting the adjuster nut to take out all ,or most, of the fore and aft
play in the forks. The adjuster nut is more about smooth side to side rotation and doesn't
tighten the fore and aft movement without the help of the cap nut.

[dougie]

I think I am wrongly expecting the adjuster nut to take out all ,or most, of the fore and aft
play in the forks. The adjuster nut is more about smooth side to side rotation and doesn't
tighten the fore and aft movement without the help of the cap nut.

I am no expert, but I disagree with that.
I believe all play should be removed by the adjuster nut (assuming that the bearings are undamaged),
and the cap nut is to hold the tripleclamp without altering the bearing adjustment.

[Chuey]

1984 RS

Is it possible that the center stem is set high in the lower yoke so the nut is running out of threads
and bottoming out before if creates any preload?

There is a lip on the steerer tube. That lip indexes into a counterbore in the bottom yoke. Therefore, unless it is not bottomed out in the counterbore, there should be no problem there.

There is a sheet metal "huge washer" flanged piece that goes onto the steerer tube before the bearing is set in place. That probably accounts for about 1mm in the length of the set up. It is kind of a dust/splash guard.

The adjusting nut and the lock nut should do the same thing when they are tightened. They act on the same threads and when tight, act as a locked in position unit to hold your adjustment. The adjuster nut should be able to make the bearings too tight if it is snugged up too far.

On my 1984 R100RS, I had to adjust a small amount of pre load into the bearings or it would shimmy at about 40mph. That is, after taking out all the play, but just only having taken out the play, and making it so it was as loose as it could be without having play, it shimmied. I moved the adjuster nut tighter by the width of one notch in the nut, or about 1/8" and it rotates smoothly and does not shimmy.

I have a stock top plate but it is very obvious to someone with your connection to the mechanical world to see what is going on with the top plate you have, so I wouldn't suspect that is a problem.

One possibility is that when the shop installed the bearings, they did not seat something all the way. It seems that tightening the bearings too tight is the most obvious way for them to become notchy. If they were not seated, but tightened too tight, they could notch while on their way to being seated all the way. Once seated, they would be loose. At least, that's one thing that it seems could have happened. The notchieness would lead me to install new bearings.

Chuey

PS I put down all the ideas that came to mind even if they seem obvious. I'm saying that as a way to say that I hope this post doesn't offend.

[Duane Ausherman]

Duane, the Luftmiester top clamp is aluminum and clamps the fork tubes, like the stock
lower clamp. I have both loose while adjusting. But unlike the stock steel top clamp with
through holes, the holes are counterbored to receive the fork tubes.

If you have both clamps loose, then the fork tubes can move to the "right place" easily and you won't be trying to bend a clamp when tightening the adjuster nut.

You are making a common mistake if I understand your comments correctly. You have both the top and bottom clamps loose while adjusting the bearings?

How do you align the fork tubes?

[Duane Ausherman]

="Chuey
On my 1984 R100RS, I had to adjust a small amount of pre load into the bearings or it would shimmy at about 40mph. That is, after taking out all the play, but just only having taken out the play, and making it so it was as loose as it could be without having play, it shimmied. I moved the adjuster nut tighter by the width of one notch in the nut, or about 1/8" and it rotates smoothly and does not shimmy.


Chuey

Chuey, I think that you may not realize what you have done. By overtightening the nut to add in preload, you are actually doing well over the required preload. The result is that the bearings are acting as a damper. It is this "damper" that is fixing the wobble, not the preload.

This amount of preload will cause the bearings to notch in short order. Also, a bike with excessive preload may have a slight weave.

Keep in mind that when the preload is adjusted on the stock set up with the thin sheet metal top plate, you still aren't finished. By then tightening the lock nut on top, you add further preload to the bearings.

This may not make sense just yet, but think about this. The threads on the center tube and the adjuster nut aren't perfect. If you have them in your hand, you will be able to feel a tiny bit of "play" of the nut on the threads. This means that as you tighten down the adjuster nut, the preload forces it to the "up" part of the play on the center tube threads. Now, when you come along and tighten down the lock nut on top, it forces the adjuster nut into the "down" position of the play on the center tube. This adds considerably to the preload.

[Chuey]

Duane, I may not have been clear about how I adjusted the bearings.

On bicycles, we adjust headset bearings as loose as they can be without having any play, or rattle. That is the first adjustment I did on my RS. That is, with everything tightened up the way it needs to be to ride it, the locknut cinched down tight, it had no play, but as well, no preload. The amount of preload was added by loosening the top nut (lock nut) and moving the one below it just that eighth of an inch clockwise at its outer circumference. That is how much preload I put into the system.

I'm used to the concept of adjusting bearings by using the tightening of two threaded pieces against each other. It may have been more clear to address the issue of the play between male and female threads on these parts. I neglected to do that because I think of that as a given.

One more thing I should have added, and the reason I looked in here again, is that the name I used for the tube that goes through the steering bearings is "steerer tube". That may be a name specific to bicycles and I thought I should say that to make my description more easily understood.

Chuey