Did you get any photos fella?
Right, I have a few shots below taken in macro, so you should get a reasonable idea of the problem. Apologies for turning the orientation of the camera but it was catch the light.
So, I first noticed last week that the steering had tight spots from lock to lock. The stiffness gave you the feel of a fifty pence piece through the arc of the turning.
I raised the bike and it was when smooth, so this indicated the lower bearing was suspect.
I removed the top clamp and bearing cap, the top bearing was fine, spotless.
Then raising the frame away from the bottom clamp exposed the problem.
You can see the seal below the bearing, very basic and sub-standard. It is a washer with a rubber skirt adherred to it. This is meant to run against the inner of the headstock tube creating a seal. The rubber had sagged away from where it was meant to seal in the headstock tube.
I then removed the corroded rollers/cage to expose the inner race.
The outer race was in similar condition, picture below in the headstock tube.
Both outer races (upper and lower) were removed from the headstock tube.
So my plan was to have my bike back on the road (off road
) asap. I obtained a pair of tapered roller bearings (SKF #30206) and made a bit of a sketch, measure what dimension I had to play with.
The idea was to make a seal of that similar to the top bearing, using a cap and o-ring. The only problem was that the lower bearing outer race sat deeper into the headstock tube, so the two sealing faces needed to be as close as the o-ring dictated.
I purchase another top cap from my local dealer. The original was machine into a flat disc/washer. This was mounted on the sterring spindle of the lower clamp and with a couple of drops of Loctitie retaining compound the lower inner race of the bearing was heated and mounted. Once the bearing was home and the Loctite had set the disc was clamped solid to the bottom yoke/clamp.
So, one of the sealing faces was the washer and the other is the outer race rim. This is similar to the top bearing arrangement.
The next pictures show the lower race with the disc and o-ring in place.
The distance that the o-ring had to move in was 3mm (checked in SKF bearing manual) so I purchased an o-ring (well, minimum order was a bag of 10 at £0.11 each) size 55x3.5 (nitrile material), this was giving me 0.5mm interferance on the o-ring, so plenty of sealing potential.
Offering the lower yoke up into the headstock tube a little care was taken not to catch the o-ring as it entered the tube.
The new upper bearing along with it's o-ring were inserted in the headstock tube.
Weight was applied to the front end until the lower bearing was home. The top cap was put on the steering spindle and then the top clamp was mounted.
Following the tightening detail in the manual the assembly was drawn together.
The lower washer had settled home perfectly giving 0.25mm nominal clearance inside the lower part of the headstock tube, and the o-ring had compressed to make a water tight seal.
The steering has returned to perfect.
I also have drilled the headstock tube and fitted a grease nipple.
So, I have my bike back rolling again, obviously this is a warranty issue but I can't be without me trail bike at present. If there is a campain by BMW to look at this issue I may persue it on a later date.
The reason for posting is to give other GX owners a heads-up on a possible problem. Please keep an eye on you bikes steering. If you begin to feel any resistance in the turning of the handlebars, this is the probably cause.
If you take a look up the headstack tube from underneath at the back of the mudguard and you can see some rusty residue appearing out past the seal (substandard) of the lower bearing. That's the tell tale sign that trouble is brewing.
I hope this has been of help.
Timpo.
