1977 BMW R100RS Replace and Adjust Wheel Bearings

A lot has been written about the procedure  to correctly set the wheel bearing preload. There is more than on technique for determining the correct preload. And wheel bearings can fail if the preload is set too low or too high. For that reason, I’ve put off setting the preload for many years and had a shop or Woody’s Wheel Works do it. But on this project, working on the wheel bearings was one of the items I had on my “Learn New Skills” list, so, now’s the time.

You can read about how I did this work here:

This bike does not have the original spoke wheels. Instead it has the cast aluminum alloy “snowflake” wheels that came latter. The rear snowflake has a drum brake while later versions of the snowflake rear wheel have a rear disk brake on the left side.

"10 Foot" View Showing Later Snowflake Wheels Installed

“10 Foot” View Showing Later Snowflake Wheels Installed

It seems that airhead wheels are a component that BMW changed a lot over the life of the airhead bikes. Further, parts fiche diagrams are notoriously confusing and frequently show incorrect parts. As I tried to get solid information about my wheels, one sage, long time wrench advised me to just inspect the parts that are there and replace what’s worn.

That said, these wheels had parts that took me some time to figure out. First, the snowflake drum rear wheels were only available with an aluminum hub in 1978. Later versions had a steel sleeve in the hub that the rear wheel bearing outer races fit into. This is an improvement as the aluminum hub to steel race interference fit was prone to allowing the race to spin in the aluminum hub which leads to a mess not to mention it can lock up the rear of the bike if the bearing seizes to the axle.

My drum snowflake rear hub has a steel sleeve as shown below. The inner edge of the hub is magnetic and you can see the line between the inner sleeve and the outer aluminum of the hub.

Rear Wheel Hub Has an Inner Steel Sleeve

Rear Wheel Hub Has an Inner Steel Sleeve

I used the spring scale method to determine the preload. This is a simple technique that is precise enough.

Pull Gauge and String Wrapped on Axle Spacer Tube

Pull Gauge and String Wrapped on Axle Spacer Tube

I had the wheels powder coated as well.  Here they are with the new wheel bearings installed and adjusted.

Rear Wheel Ready To Roll

Rear Wheel Ready To Roll

Front Wheel Ready to Roll

Front Wheel Ready to Roll

4 thoughts on “1977 BMW R100RS Replace and Adjust Wheel Bearings

  1. Thank-you for posting this. I enjoy the style and detail in how you walk through this.The photos and videos are an added plus.Still a project at the edge of my skill set,but with more than one airhead to maintain I should be having a go at it. I live in an area some distance from any BMW shops,so the web is my best source of info. Thanks again.

    • Hi Don,

      You’re welcome. I hope to work on a wheel with an aluminum hub in the future as the procedure to remove the bearing stack is different. I’ll post that work when I complete it.

      Best.
      Brook.

  2. My snowflakes are out for silver Powdercoat now. Can you describe how glossy the finish was on yours? Mine will be almost as glossy as a polished chrome rim.

    Can you describe how the pull gauge works to measure the pre-load?

    The bearings I removed were in good shape. Can I risk re-installing them or just go ahead and bite the bullet for new ones? Any suggestion for bearing dealers that can beat BMW prices? Thanks as always and keep up the good work!

    • Hi John,

      The snowflakes did not have a high gloss finish as would occur with a clear coat layer on top of the color coat. I opted to not use a clear powder coat layer over the color for that reason. That said, you can do whatever pleases you, as it’s your project 🙂

      The video clip embedded in the write-up illustrates what I did, or at least that was my intent. I found that pulling evenly and steadily over a distance of 6-8 feet walking away from the wheel gave a steady reading starting about 1/2 way through that distance.

      The bearings should last “forever” if they were greased regularly. I had one that was notchy, but opted to just replace them all due to the evidence of the bike being neglected at one point in it’s life.

      I bought mine at Cycle Works. Independent bearing suppliers also sell these as they are a common tapered roller bearing. My bearing house was 15% more expensive than Cycle Works, so I went with them. YMMV.

      I hope this helps.

      Best.
      Brook.

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