1975 R90/6 Front wheel questions

[bandersnatch]

Hi all,

After waking up my R90/6 after a 25-year slumber I'm in the process of getting it road ready. While tearing down the front wheel for new tires and spokes I ended up with a few questions.

1. Wheel bearings. They seem fine, spin well with no grinding and appear to not have any significant wear on the rollers or roller surface. Should these be replaced as a matter of course, or would you all clean them up and re-use? Also, the bearing surface inside the hub appears to be pressed in, if the consensus is to replace bearings and associated bits, is tapping them out from the back side the proper removal method?

2. Upon disassembly, I found the rotation arrow on the rim was pointed backwards (opposite the rotation of the tire). I don't know the history of the bike, but it appears completely original and I don't have any reason to think the wheel has been worked on previously. Could it have come from the factory that way or is it a DPO error? Not an error? Very confused on this one . . .

3. The center hub appears to be symmetrical, true or not? In other words, if I send it out to be media blasted (it's quite ugly right now) and my left/right markings get cleaned off is there a way to tell which side is right/left or does it matter?

4. How is the rubber wheel bearing seal installed? It appears to be pressed in, but from the front or back side? Being rubber, I want to replace them (as well as the thrust ring as they do have some grooves scratched in them) but don't want to destroy anything by improper removal.

Thanks in advance,

Larry

 

[bandersnatch]

Okay, it looks like the parts fiche answered my last question, the seal appears to be a one-piece unit meaning the entire piece gets replaced, not just the rubber. True, or am I not reading the picture correctly?

 

[20774]

Larry -

Wheel bearing service should be researched thoroughly...making a mistake can quickly destroy the hubs and/or bearings. Here are some places to read to get a feel of what's going on:

Snowbum's site...more then you can imagine! - https://bmwmotorcycletech.info/section4.htm

Duane's site...might be more applicable to the /6 hub - https://w6rec.com/the-5-wheel-bearings/

For snowflakes, but good documentation - https://forums.bmwmoa.org/showthread.php?46970-Wheel-Bearing-Replacement-Snowflakes

I suspect Brook has a good description of the whole process.

As for the tire rotation, reversing the arrow is probably what should be done for a tire that was designed for rear wheel operation. Usually though, inch-size tires can be found for front tire application in which the arrow should follow the tire rotation

About the seals, I would think that's fairly obvious. I don't remember exactly how the side that faces the bearings is, but that's typically an open section which a spring wrapped around the inside to keep it against the axle...maybe that's not completely correct. But from the outside, it all should be fairly smooth and flush with the outside of the hub.

 

[nickrides]

Wheel Bearings
If they look Ok and turn Ok I'd clean them and reuse and regrease them.
Replacing them is a major PITA operation IMHO.

 

[20774]

The bearings can be greased in place. Cycleworks sells a tool that will push grease into the bearings. Could be a good thing to get new gease but it might just push bad stuff deeper. As Nick said, if they feel fine maybe a shot of grease would give peace of mind.

 

[bandersnatch]

Thanks for the advice guys, I'll give the bearings a thorough cleaning and re-grease. I have the entire hub stripped down, I actually found it pretty straight-forward overall. I was fortunate to have an adjustable pin wrench to remove the chrome bearing covers.

Kurt, I'll be sure to read up on the articles you listed before reassembly. Definitely don't want to screw anything up. I did look at Brook Ream's pages briefly but they mostly refer to the /5 with drum brakes rather than the disk brake hub on my /6.

Just to be clear, the arrow I was referring to is the one stamped inside the rim rather than the one on the tire. My understanding is both arrows should point in the direction of rotation, but my rim had the arrow pointing the wrong way. It appears that the bike was that way from the factory so it doesn't appear to have affected anything but I'd prefer to put it back together correctly.

 

[20774]

OK...arrow on the rim. Can't say as I've ever seen it. But Snowbum talks about the arrow about midway on this page...or search for "arrow" in your browser:

https://bmwmotorcycletech.info/section2A.htm

 

[shandeland]

If you ever decided to replace those bearing the inner race must be taken out after heating the hub. Be sure to read those links that were posted before dong it.

 

[swall]

The arrow on the rim only comes into play for the dual disc models. It is there so you can put the wheel back in the same orientation and not have to re-adjust the calipers. Putting the wheel back with the same orientation insures that the brake pad wear pattern will remain the same.

 

[THOMASPIN]

If you decide to stick with the current taper roller bearings they can be easily removed by removing the disc (5 locking nuts - replace those) and removal of the chrome cover either side, the one with the four pin holes in it. This will permit thorough cleaning in a volatile solvent.

Duane Ausherman illustrates the use of pin punches in lieu of the four pin tool here. Alternatively, Cycleworks sells a four pin tool which even has a thread for a through bolt to keep the tool in contact with the chrome retainer ring. Handy if it's stuck after all those years.

Once you have clean, greased bearings installed, the bearing greaser Kurt is referring to can be found here. This works in conjunction with your grease gun. Give the bearings a fresh shot when the wheel is off for tyre replacement. No need to remove the chrome rings or brake disc(s).