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Old 09-08-2009, 08:29 AM   #271
tmex OP
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After thinking about this and doing some research, I am not convinced that the crush for a ball bearing is all that critical. I think a tight fit is more likely to result in damage to the bearing when it is installed. What we may be seeing here is simple installation damage particulalry if the installer is using a tool which might contact the inner race of the bearing. The fact that the rotor side of the rear hub seems to be machined tighter is consistent with this theory.
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Old 09-08-2009, 09:45 AM   #272
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Quote:
Originally Posted by tmex
After thinking about this and doing some research, I am not convinced that the crush for a ball bearing is all that critical. I think a tight fit is more likely to result in damage to the bearing when it is installed. What we may be seeing here is simple installation damage particulalry if the installer is using a tool which might contact the inner race of the bearing. The fact that the rotor side of the rear hub seems to be machined tighter is consistent with this theory.
I do not know how much impact a tight fit has on a bearing, maybe some engineer can speak up. Machine tools certainly wear and if quality control does not pick it up, it gets passed to the consumer, or perhaps it was within specs and the engineer was wrong.
The one thing I am becoming more convinced of, is that BMW will be less than forthcoming. If you contact BMW corporate about issues like this, I guarantee you, that the answer will be, that these are quailty bikes and that they continuosly improve them. I take examples of this thinking as evident with the apparent handling of other complaints like the bending sidestand where it appears they have strengthen the bracket and apparently will sell it as soon as existing stock is used up. Or the breaking chain issue as discussed on ukgser where the chain was improved and made available for sale this August, under the radar.
I guess this is just how big business operates, do a cost analysis and roll the dice. They obvisiouly are improving the bikes and the warranty has been good so far, so I guess I am a glass half empty kinda guy.
Personally I hope it is the tight fit of the bearing caused by machinery wear, as few bikes will be affected, though it does leave buyers of those bikes in the lurch.
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Old 09-08-2009, 10:43 AM   #273
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Quote:
Originally Posted by JoelWisman
Hi guys. Crush factor is important but it is not what most people think it is.

All bearing manufactors list a maximum radial crush. This specification is generally between .0005" and .0015" and is how much the bearing can be crushed and still function adequately.

If the bearing were installed into a seat made of very thick hardened steel then it would be straight forward. If the bearing is installed into something softer and less strong, such as our aluminum hubs then the undersize of the seat can be greater as the seat will expand some. How much smaller in this case, I do not posses the math skills to determine.

As for BMW not being informative about updates and improvements. No they certainly are not! That said, what manufacture is? None that I know of. Do I wish they were informative? Hell yes! But I accept they are not, to do otherwise is to wait for a train that don't come.
Crush is usually specified for journal bearings i.e. connecting rod bearings. In the case of a steel ball bearing pressed into an aluminum hub I don't think it is at all critical. If anything will be sacrificed in this case it will be the hub or the bearing could get stressed during the install process. One thing is certain, the rotor side bearing is not going to move in the hub once the assembly reaches ambient. If the install process involves pressing the bearing in until enough hub ID is showing to get the snap ring in, then inserting the snap ring, and then pressing the pair in until the snap ring "snaps", then the rotor side bearing may not be seated deeply enough to contact the spacer between the bearings. In this case the rotor side bearing will get axially loaded when the axle is torqued, and will eventually self-destruct. That is my theory, and I am sticking to it.

I will add that the rotor side of the hub may be machined incorrectly in two possible ways. First, and I say this from experience, the bearing seat is too deep relative to the snap ring grove. It is possible to install the snap ring with the bearing outer race not seated. Second, I think the ID is a bit too small. When you need to freeze the bearings and heat the hub to get them in, that is too tight.
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Old 09-08-2009, 11:38 AM   #274
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When the axle is tightened the spacer should support the inner races of the bearings unless the spacer is too short. Then the axle tension turns into radial load on that bearing and voila you have premature failure. The spacer should be reasonably snug like 0.025" clearance so you can angle it to punch out the old bearing.
Any more play and you have significant radial load on the bearing since you never tighten down on the spacer.
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Old 09-08-2009, 02:10 PM   #275
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Yesterday I pulled my rear wheel off to do a bearing check. All three of my rear wheel bearings felt good although I'm not a bearing expert there didn't seem to be any notchiness. I did find a small amount of a white grease on the bearings. I only have about 3600 miles on the clock so maybe too early for failure. I did notice that the rubber connectors between the cush's in the rear drive were broken.

I called my dealer and asked about them looking at my bearings they offered to do what they call an "inspect and advise" the charge is one hour labor.

I too have checked the rear disk side of the hub for heat after a commute through traffic, it was cool to the touch.
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Old 09-08-2009, 05:06 PM   #276
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Quote:
Originally Posted by JoelWisman
Hi guys. Crush factor is important but it is not what most people think it is.

As for BMW not being informative about updates and improvements. No they certainly are not! That said, what manufacture is? None that I know of. Do I wish they were informative? Hell yes! But I accept they are not, to do otherwise is to wait for a train that don't come.

I know you are right, and I am sure I sound like Peter and the Wolf anyway, so I am quitting my BMW bashing. What originaly set me off was a response from BMW on a subject i have never commented on, but I agree, enough is enough.
On a positive note, I took my bike on a little ride yesterday and good suspension sure changes your outlook on the bikes qualities.
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Old 09-08-2009, 05:26 PM   #277
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I guess there is a whole thing going on with the rear wheel bearing. A bulletin ? and other failures?
dchttp://f800riders.org/forum/showthre...hlight=bearing
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Old 09-08-2009, 05:37 PM   #278
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bearing removal

I could use a few hints on how to remove the bearings
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Old 09-08-2009, 05:57 PM   #279
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Quote:
Originally Posted by wscollay
I could use a few hints on how to remove the bearings
The bearings are easy to remove if you don't mind destroying them. Just push the spacer aside and pound them out with a 3/8" drive socket extender or anything else that will fit through the inner race and is strong enough and long enough. Getting them out without destroying them (especially the rear rotor side bearing) is not possible IMO. Even if you take a torch to the hub the bearings are very tight, and would require too much force on the inner race using a blind bearing removal tool to reuse the bearings.

Be sure to remove the snap ring on the rotor side rear bearing.
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Old 09-08-2009, 06:32 PM   #280
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Quote:
Originally Posted by tmex
The bearings are easy to remove if you don't mind destroying them. Just push the spacer aside and pound them out with a 3/8" drive socket extender or anything else that will fit through the inner race and is strong enough and long enough. Getting them out without destroying them (especially the rear rotor side bearing) is not possible IMO. Even if you take a torch to the hub the bearings are very tight, and would require too much force on the inner race using a blind bearing removal tool to reuse the bearings.

Be sure to remove the snap ring on the rotor side rear bearing.
If you use this method make sure you pound them out evenlyotherwise it would be easy to damage the hub!!! If you damage the hub you will have a nightmare, proper tools recommended.
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Old 09-08-2009, 07:50 PM   #281
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Keep two things in mind; first my inner spacer was touching both bearings. second, the disc side bearing got smoother when it was removed. I think the excessive crush has a big effect on the bearing.
I took the bearings across the street to Kaman, when I mentioned that it come out a motorcycle wheel they no longer had an opinion on the cause of the failure( sissies).
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Old 09-08-2009, 08:02 PM   #282
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Originally Posted by EnderTheX
If you use this method make sure you pound them out evenlyotherwise it would be easy to damage the hub!!! If you damage the hub you will have a nightmare, proper tools recommended.
Proper tools are always a good idea. I do have a blind bearing removal tool, but even with heat applied to the hub it would not take out the rotor side bearing. I had to use some persuasion from the other side. Other folks may have had different experiences - don't know. Nonetheless, the blind bearing removal tool applies all of the removal force to the inner race so I would be skeptical of using the bearing again if it was really difficult to remove with this tool. I don't know of any other tool that you might use. Suggestions welcome.
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Old 09-08-2009, 08:29 PM   #283
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I got them out. The one on the drive side seems ok, the one on the rotor side was very rough installed but smooth when removed? Now I suppose the spacer has been pounded a little shorter. The whole thing seems way too tight. Take some emery cloth to the hub to make it a little looser. I keep looking at the bike, it still is a BMW not a Fiat.

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Old 09-08-2009, 09:05 PM   #284
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Wish I had more guts, I'd machine out the hub a tad and test it out...
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Old 09-08-2009, 09:23 PM   #285
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Just emery cloth out a thousandth or so. You cant remachine it at this point.
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