Educate me re: steering head bearing adjustment

[lhead]

At the outset, forgive me. I'm a new BMW owner after years of Japanese bike owning and wrenching. I believe I discovered a big part of my K1100rs's handling ills this weekend - very notchy steering head bearings. A handlebar centered detent had developed that was very pronounced. So, Saturday the triple tree came out for cleaning, inspection and re-greasing. No rollers were damaged nor were the races. Cleaned all, relubricated and reassembled. I read and re-read the BMW instructions for setting the bearing adjustment. I made a thrust collar and did it the way the instructions said. After all was done and torqued, I think the bearings are still a little loose. The reason I say that is that the triple tree bounces slightly off the stop if it's allowed to fall to the stop from center. I always use the "bounce test" as a way to determine proper adjustment. Does this apply to BMWs as well?

Secondly, I'm wondering exactly how the three pieces work to affect steering head bearing adjustment. Does the knurled ring at the bottom apply bearing preload? If so, what's the purpose of the externally threaded plug in the center? And, if the knurled ring applies preload, what's the procedure for initial setting of the ring?

Bonus question - what's the purpose of mounting the brake rotors on plastic pins?

Sorry for the ignorance, but I've found that the two paths to knowledge are the asking of questions and the making of mistakes.

Thanks everyone.

Charlie

 

[Scott_]

Well, the brake rotors aren't on plastic pins, they are aluminum, or they are from the factory.
You have to have something give from heat expansion, since the calipers are bolted solid to the forks, that only leaves the rotors to be able to "float" for expansion and contraction with braking heat dissipation.

[Rick G]

The bearings adjust just as they do for any other bike  I would do them a bit tighter than the bounce if they are packed with grease, I usually test the bearings so that they are easy to turn but if pushed don't turn futher when you stop pushing.
The threaded insert is just to have a thread to tighten the nut on the top clamp. When you tighten that nut be sure to check that it hasn't made the bearings over tight as when the thread is worn a bit it can do that so if that happens a bit of trial and experiment as to just how tight it needs to be.
As Scott said the bits that hold the disc to the mounting plate are aluminum and if you can feel any play when cold then they need to be replaced.
OEM are aluminum and you can get stainless spools from Motobins in UK.

[lhead]

Sorry, I just assumed plastic. Aluminum makes more sense. Thanks.

[552255]

I too found the steering head bearing procedure a bit confusing, with the thrust collar, as i ended up with a large channel locks just tightening the knurled lower ring, and couldn't get the thrust ring method to 'work' per se...and then tightened up the stem and lock ring.  You can feel the change in motion when tightening/loosening the large knurled ring, and i could feel no change after  tightening the lock nut.  Seems to be working fine, after 1000 mile long weekend.  I elevated the front wheel and lifted up to see if there's any play in the stem/tree as a check.

The bobbins up front can be rotated to diff. positions, i have side to side play, but no back/forward play, which is the sign that they are wearing.

[Rick G]

The bearings adjust just as they do for any other bike  I would do them a bit tighter than the bounce if they are packed with grease, I usually test the bearings so that they are easy to turn but if pushed don't turn futher when you stop pushing.
The threaded insert is just to have a thread to tighten the nut on the top clamp. When you tighten that nut be sure to check that it hasn't made the bearings over tight as when the thread is worn a bit it can do that so if that happens a bit of trial and experiment as to just how tight it needs to be.
As Scott said the bits that hold the disc to the mounting plate are aluminum and if you can feel any play when cold then they need to be replaced.
OEM are aluminum and you can get stainless spools from Motobins in UK.

I should clarify here I am talking with no front end in and just the bare tripple clamps