WHERE DOES THIS PART GO????

[chasbmw]

Would expect discoloration from heat.

'Spose so.

Could also be the result of wrong preload setup from factory.
Or wedding band left out during noob maintenance.
The sacrificial bearing, one will take it for the team.
That sort of damage is going to generate heat too.

Whatever the cause, it doesn't matter. Fix it.

The left hand bearing tends to collect more road crap and water, especially if seal was not fitted or worn. The right hand bearing is much more protected

[ibjman]

I have it all reassembled.
I did remove the SKF bearings (30203J2/VT108) - both- and install genuine parts from MAX BMW:
(+MARK+ SWISS 30203).
There was some question about the outer "Radius" of the J outer bearing race. I put the old J bearing race back to back with the new Swiss bearing. I can see no visual difference with the naked eye looking at both radii together.

As to the wedding band spacer. I ordered 3 spacers from MAX as follows: 1 that was 1 size smaller than the one I measured that I took out, 1 that was one size larger than the one removed and 1 that was the largest one they sell.
After installing the new bearings, it was found that the "1 larger" I had purchased was actually the same size as the one I took out (no value).
With the new bearings and the original spacer the bearings were obviously way too tight. Since my intended 1 larger spacer was actually identical, I had no choice but to sand the thickness of my "largest" spacer down, a little at a time and use trial & error method to establish a preload.
The original spacer measured .270 (actual .267) = 6.70mm.
The spacer I ended up with, after sanding down measured .2835 =7.20mm.
By my calculations, I had to add .5mm to the overall spacer width to achieve an acceptable preload.
I think that anyone who has ever attempted this would tell you it's not an "exact science" by any measure.
I used the pull string method with the gram spring scale on an approx. 1.5" axel dia. as suggested in the article that was linked from this forum.
I ended up with a pull force between 600 & 800 Grams (I'll call it 700). I believe the specs that I was shooting for was like 937 grams??? Anyway, I ended up with a smaller preload than hoped for but the "hand feel, years of experience method, tells me that it's just about right. My consensus is that the old bearings were set up too tight and or that the inner race on the left side may have been defective.
I'll be sure and let you guys know, if I prove to have been wrong.

Moving on to the front end.
After having the bike tied down at the front on the lift for a couple of weeks and having the weather turn substantially cooler, a quick road test of the rear wheel mx. showed something VERY wrong with the front steering. I could barely turn the forks by had with the wheel off the ground and the steering was extremely heavy from the bars. I definitely felt that I had a failed steering head bearing as in "broken".
Inspection revealed that the steering head bearings were simply dry & sticky, the grease inside having deteriorated to the consistency of GLUE. Even with my years of experience in automotive, I never would have guessed that bearing grease could possibly get that "stiff"!!! Further inspection revealed that the races etc. were still in good shape with little of no Brinelling. A good cleaning and fresh grease seems to have corrected that completely.
Continuing, The front wheel bearings were removed for inspection.
These bearings looked to be in good condition with plenty of grease. They were also packed with "blue grease" as was found in the rear. They are the same SKF 30203J2/VT108's that were found in the rear. The only problem found is that the right front top hat spacer had been installed upside down with the shoulder "out" The bearings were repacked with grease and reinstalled with new BMW seals. I found the upgraded BMW seals that are totally rubber encased to be extremely difficult to install straight being almost too large and wanting to cock sideways when being driven in. I ended up with them driven in a bit too far so I'm hoping they'll be ok????
I liked the metal jacketed seals that came out much better!
More later.......
Regards, ibj...

[PITAPan]

I have it all reassembled.
I did remove the SKF bearings (30203J2/VT108) - both- and install genuine parts from MAX BMW:
(+MARK+ SWISS 30203).
There was some question about the outer "Radius" of the J outer bearing race. I put the old J bearing race back to back with the new Swiss bearing. I can see no visual difference with the naked eye looking at both radii together.

As to the wedding band spacer. I ordered 3 spacers from MAX as follows: 1 that was 1 size smaller than the one I measured that I took out, 1 that was one size larger than the one removed and 1 that was the largest one they sell.
After installing the new bearings, it was found that the "1 larger" I had purchased was actually the same size as the one I took out (no value).
With the new bearings and the original spacer the bearings were obviously way too tight. Since my intended 1 larger spacer was actually identical, I had no choice but to sand the thickness of my "largest" spacer down, a little at a time and use trial & error method to establish a preload.
The original spacer measured .270 (actual .267) = 6.70mm.
The spacer I ended up with, after sanding down measured .2835 =7.20mm.
By my calculations, I had to add .5mm to the overall spacer width to achieve an acceptable preload.
I think that anyone who has ever attempted this would tell you it's not an "exact science" by any measure.
I used the pull string method with the gram spring scale on an approx. 1.5" axel dia. as suggested in the article that was linked from this forum.
I ended up with a pull force between 600 & 800 Grams (I'll call it 700). I believe the specs that I was shooting for was like 937 grams??? Anyway, I ended up with a smaller preload than hoped for but the "hand feel, years of experience method, tells me that it's just about right. My consensus is that the old bearings were set up too tight and or that the inner race on the left side may have been defective.
I'll be sure and let you guys know, if I prove to have been wrong.

Moving on to the front end.
After having the bike tied down at the front on the lift for a couple of weeks and having the weather turn substantially cooler, a quick road test of the rear wheel mx. showed something VERY wrong with the front steering. I could barely turn the forks by had with the wheel off the ground and the steering was extremely heavy from the bars. I definitely felt that I had a failed steering head bearing as in "broken".
Inspection revealed that the steering head bearings were simply dry & sticky, the grease inside having deteriorated to the consistency of GLUE. Even with my years of experience in automotive, I never would have guessed that bearing grease could possibly get that "stiff"!!! Further inspection revealed that the races etc. were still in good shape with little of no Brinelling. A good cleaning and fresh grease seems to have corrected that completely.
Continuing, The front wheel bearings were removed for inspection.
These bearings looked to be in good condition with plenty of grease. They were also packed with "blue grease" as was found in the rear. They are the same SKF 30203J2/VT108's that were found in the rear. The only problem found is that the right front top hat spacer had been installed upside down with the shoulder "out" The bearings were repacked with grease and reinstalled with new BMW seals. I found the upgraded BMW seals that are totally rubber encased to be extremely difficult to install straight being almost too large and wanting to cock sideways when being driven in. I ended up with them driven in a bit too far so I'm hoping they'll be ok????
I liked the metal jacketed seals that came out much better!
More later.......
Regards, ibj...

I'm wary of the words "genuine parts".It is often just marketing BS. For a standard part, like those bearings, it's just a matter of who you are buyingh from. BMW does not make them, they buy them from a MFG, mark them up a lot and resell them through their dealers. Sometimes the dealers skip getting them from BMW and pocket the markup themselves. other times you can buy a special part from the same vendor that is making them for the OEM. Asin water pumps for Toyotas for example. You can by Chinese aftermarket ones, or you can buy Asin, either from a dealer ($120) or any other source selling them ($60). The Chinese ones are $20 and don't last a long time, although they are accurate dimensionally.

Some to-far is ok on the seals---they will just be running on a fresh surface on the top hat. This is done intentionally some times. After you insert the top hat through the seal (AFTER the seal goes in) make sure you can move the top hat inwards and outwards a bit. That's good. You don't want it bound up in that direction.

Silicone lube on the seals, then press them with a 3" x 3" (or larger) piece of 1/2" plywood. Ideally baltic birch. Using the larger plate gives you a very sensitive feel for the angle and you can both hold it flat and lean on it. You will never press them past flush.

[ibjman]

Thanks, Sounds like good information.....I'll keep that in mind next time, especially the Baltic birch custom seal installer.
As for the bearings...... I went with my best gut feeling on this given the huge controversy about the parts that came out.
I've always had great service from MAX BMW and I trusted them to send me the proper MFG. recommended parts on the bearings. Good point about the top hat spacer......I may have a problem there especially since we already know that the seal is installed too deep. I guess I'll find out soon enough if the wheel starts streaking grease out all over after I ride it some.
I'm guessing the last guy in there just forgot to install it in the seal before driving the seal home so he just stuck it in backwards as an after thought.....especially given some of the other conditions I found.
Thanks, ibj...