I’m going to powder coat the wheels, so I remove the disk brake rotors I refurbish the three rotors to remove grunge and get the patina on the disk carriers back to factory condition. I also clean out the holes and sand the disks so the new disk pads will bed in and not get fouled from brake pad grunge baked on the rotor or dirt and grunge lodged inside the disk brake rotor holes.
I also removed the wheel bearings before having the wheels powder coated. There is a separate document about how to replace the wheel bearings.
I replace the two rear wheel safety straps with tabs that are bent along the side of the bolts to keep them from backing out. I treat these as a “use once” part.
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Here is a short video summarizing this work.
VIDEO: 1983 R100RS Remove-Refurbish-Install Disk Brake Rotors
Remove Rear Rotor
The rear wheel has a single brake rotor on the left side of the wheel. It’s bolted to the wheel hub with five hex head bolts. These bolts are in blind holes so there are no nuts. The bolts are secured with metal strips with tabs that bend over the face of the bolts to prevent them from turning.
I use a screw drive and hammer to flatten the metal tabs on the strips. Then I remove the five bolts.
The brake rotor and it’s hub pull off the center hub of the wheel.
Rear Wheel Details
The left side of the rear wheel hub is dished and the right side has a flat hub where the disk brake rotor mounts.
On the left side of the wheel are a number of markings including an arrow showing wheel rotation. The numbers that look like 11 digit part numbers are not part numbers, they are casting numbers. The markings indicate the rim is 2.75 inches x 18 inches.
Remove Front Brake Rotors
There are two disk brake rotors on the front. They are not marked “Left” or “Right”, but they have mated to the disk pads. In general, it’s a good idea to keep them on the same side when you reinstall the rotors so the disk brake pads don’t have to bed in again on a different rotor.
I’m replacing the caliper pads, but I mark the rotors so I return them to the same side I removed them from. Why Not?
It’s easy to damage the rotors if you place them on the ground or work bench when you work on the wheel. I use some 2×4 blocks under the rim to keep the faces of the disk brake rotors off the floor. The rotors are thin and you can bend them if you aren’t careful.
There are five Allan bolts with locking nuts that secure both rotors. The bolts go through the wheels. The lock nuts are on the left side of the wheel and the Allan bolt heads are on the right side of the wheel.
I remove the five bolts. The disc brake rotors pull off the hubs the same way the rear brake rotor did.
Front Wheel Details
One important item to verify with these cast, aka “snowflake”, wheels is that it’s one of the reinforced ones and not the original design. BMW still will replace the original snowflake with the reinforced version. These wheels are the reinforced version due to the web along the main spoke from the hub to the rim as you can see in the two pictures below. You will find a picture of the recalled defective design in this article posted by Bob Fleischer, aka “Snowbum”:
The center hub is different on the left side and right side. The left side, which is the side with the locking nuts on the five Allan brake rotor bolts, has five webs from the bolt holes to the center hub. The right side hub is solid.
The left side rim of the front wheel has a number of markings. It does not have an arrow indicating the direction of rotation as the rear wheel does. The numbers that look like 11 digit part numbers are not part numbers, they are casting numbers. The markings indicate the rim is 2.15 inches x 19 inches. The left side of the wheel is the side with the five ribs around the center hub and is the side the brake rotor nuts are on.
Powder Coat The Wheels
Due to the intricate pattern of the cast snowflake wheel, I have them powder coated. It’s hard to get complete, even coverage spray painting them.
There are two schools of thought about powder coating: It’s not a good idea; It works well. One issue is what do you do when the powder coat gets chipped. I use matching paint to fill in the chip and that seems work well. The other thing to consider is powder coating on steel, when it chips, opens up a location for corrosion to start and if you neglect it, it will eat it’s way under the powder coat. Since I live in dry climate, and these are aluminum alloy wheels, corrosion is not the problem it would be with steel as aluminum oxide stops corrosion at the surface.
Since this bike is not a restoration, but a build staring from an RS and ending up with an RT, I’m taking some liberties with the paint and powder coat. I like the white wheels on the R65LS and I think white wheels lighten the stance of a bike. So, I had the wheels powder coated in matte white.
Refurbish Disk Brake Rotors
I use my small Harbor Freight bench top blasting cabinet to clean up the brake rotor carriers. They are pretty grungy and have some corrosion. I estimate that the air pressure is about 40 PSI so the glass bead is not too aggressive.
Very fine glass shards exit the cabinet and go everywhere. For that reason, I NEVER blast inside my shop. The cabinet is on casters and I roll it down the driveway and do my blasting there. I always wear an N95 face mask and eye protection. You do not want to breath fine glass into your lungs or get it into your eyes.
There is a mark on the back of the rotor carrier. “MIN 0.18”, that shows the minimum allowed rotor thickness; 0.18 inches (4.6 mm). I measured the rotor thickness and I have about 5 mm on the front rotors and close to 6 mm on the rear, to these have quite a few more miles left.
Next, I use 400 grit wet/dry paper and sand both faces of the rotor. I do this to remove any cooked on residue from the brake pads so the new pads will bed in correctly.
Then I use Q-tips and spray the end with a bit of brake cleaner. I clean out the inside of all the holes in the rotors. These accumulate grit, dirt and binder from the brake pads and this can foul new brake pads preventing them from bedding in correctly.
Install Disk Brake Rotors
I install the five Allen bolts, flat washers and lock nuts that secure the two disk rotors to the wheel. I make sure I return the rotor to the side of the wheel it came from as I labeled the rotors when I removed them. I torque the bolts to 17 FT-lbs,
On the rear wheel I install new safety strips with the tabs that lock the rear hex bolts and keep them from rotating. I torque the bolts to 17 FT-lbs.
Here are the wheels after powder coating and installation of the disk brake rotors. I think it’s a major improvement of the wheels from what I started with.
2020-05-04 Added note about wheel bearing replacement.
2020-06-04 Fix error in rear wheel bolt type-Hex rather than Allan.