Slash 5 Rear Wheel Question

[vespajg]

Last night, I was installing my rear wheel after a tube change and a small "top hat" shaped washer (spacer) fell out of the drive side of the hub (at least that's where I think it came from). It apparently was held in place with residual grease from the hub. Clymers appears to call this a thrust washer, or some such thing, but pictures it on the non-drive side of the hub in the blow out diagram. Due to its shape, I am certain it is not a "cigar band" spacer or from the internals of the hub (unless it's supposed to be inside the stack and the hub needs to be disassembled to get it there).

FWIW, I did not disassemble the bearing stack, but the spacer fit perfectly into the axle hole on the drive side of the hub with the "top of the top hat" oriented towards the hub (this orientation appears to be different than the Clymers blowout diagram, but I'm not even sure I'm looking at the right part in the diagram). But it fit perfectly, and I could not find any other place where it could have come from - either in the hub or the final drive. The wheel installed correctly and the moto is up and running with no apparent problems. I took the axle out again to see if the wheel would install without it in place and the hub appeared to bottom out on the final drive, so I put it back where I believe it came from.

Just wondering if anyone can chime in with an "amen" so I can quit thinking about it, or a "what have you done" so I know I need to fix it.

Thx in advance.

[Schnell]

Sorry, I've either lost the "top hat" a long time ago or mine never came with one.


Ken

[Frog]

Sounds like you got it right.

It looks like this:

http://w6rec.com/duane/bmw/wheel_bearing/tophat.JPG

You have one on each side....though their sizes are different.

Here are both together:

http://w6rec.com/duane/bmw/wheel_bearing/tophats.JPG

I have seen them mounted with the brim of the hat inside the seal....or outside. If outside, they do fall out, as you now know. I makes no difference in terms of bearing compression which way you put it. You can decide which way you prefer it, in terms of sealing out dirt. I put mine inside the seal.

[vespajg]

Thanks, Frog. That makes me feel better.

My tophat was the one on the right in the second picture. And I scoured Duane's site looking for something like that but could not find it!! I knew I had seen it somewhere, but slow connection = not much patience in searching!!

Thanks again.

[vespajg]

Another question after thinking about your post. On my bike, the taller tophat must have be installed on the inside of the non-drive side as I didn't see a tophat there when I removed the wheel and I'm pretty sure one didn't fall out. A quick read of Duane's website seems to indicate that the taller one is the one that usually falls out. I guess the installation of mine is reversed from what he indicates, which presumably results in the same preload on the bearings?

[Duane Ausherman]

The length of the top hat has nothing to do with the pre-load on the bearings. They are close in size and swapping them around will only shift the wheel a bit to one side. As long as it doesn't rub on something, then don't worry about it.

[vespajg]

Thanks, Duane and others. Very helpful. By rub on something, do you mean the swingarm, etc? Or should I be listening closely to the hub? It all appears to be running smoothly and quietly . . .

As everyone I'm sure has experienced, my 30 minute repair - wheel installation/speedo cable replacement - ate up most of my evening. But the flat is fixed (properly mounted and balanced, Duane) and the speedo is now so steady that it looks to be frozen as I go down the highway!

[Duane Ausherman]

AS it moves to the left, the tire would rub on the swing arm. As the wheel moves to the right, the hub would rub on the final drive. It sounds like you have avoided both.

The top hat only serves to carry the pressure past the seal and to the bearing. They can be installed either way around. The /5 had the brim (wide part) on the outside. That protected the bearings from water and dirt to some extent. The downside is that it easily fell out and got lost. Then on the /6 they moved it to the inside of the seal. They didn't fall out, but protected a bit less. I prefer the /5, but that is because I know about it falling out and take care to avoid that.

I still have never seen a worn out tapered wheel bearing on a BMW motorcycle. Many are damaged by water, or some idiot's handling, but they don't wear out. Even if badly pre-loaded, they will ruin a hub, but the bearing is still good.

[vespajg]

Thanks again, DA. Is it safe to assume that if one of the tophats was missing (either one), the wheel would not tighten up properly and/or be improperly positioned and result in rubbing as you've pointed out.

[Duane Ausherman]

It is possible to tighten up ok, but only if the axle is pulled further through the final drive by an amount equal to the height of the top hat. Then that amound of threads would stick out the nut. I would take a serious look at the seal wear.

Only a blind person could miss that situation.