Floating Disk Roller Replacement

By Buzz Davis
April 2001 (Addendum 1 added November 2001, Addendum 2 added August 2005.)

Replacing rollers, washers and circlips on the front wheel of a 91 K100RS-ABS with floating discs.

At 60K miles I noticed the floating rotors on my K were beginning to rattle indicating some wear in the interface of the suspension system of rollers between the rotor and carrier. The normal looseness was more than what I thought acceptable. The rotors could be moved approximately 1/32" laterally and 1/16" to 3/32" front to back. Upon consulting the Clymer's K manual there was no mention of how to do this job or what the acceptable lateral and front to back tolerances were. So, with no knowledge as to how to do this I was off to my local BMW dealer to get the parts to do the project.

Here is what you will need:

18 Part # 34-11-2310-086 Roller
6 Part # 34-11-2310-995 Roller with snap ring
24 Part # 34-11-2310-089 Circlip
24 Part #34-11-2310-088 Washer

Total cost of the parts was around $110.00 with PA. State tax.

On to the project: I got out the Clymer's manual (M500 edition) and proceeded to attempt to remove the Brembo brake calipers. You really ought to have the Clymer's manual. It has pictures and words to instruct you how to do most of the service procedures. Worth having.

I removed the belly pan, put a jack under the oil pan and cranked the front wheel off the ground. Per the instructions I removed the two brake caliper assembly mounting bolts that secure the caliper to the front fork on each side. After about a half an hour of trying to tilt the caliper and remove it per the manual's instructions I was stumped. The caliper/wheel clearance on my K is such that the calipers cannot be removed. There is insufficient clearance from the top of the caliper to the inside of the wheel to do this.

So, next best thing, I just took the front wheel off. To remove the front wheel you need to loosen the caliper mounting bolts, the 4 front axle clamping bolts, and the special bolt and washer from the left side of the front axle. Then you take a drift or Phillips head screwdriver put it in the hole on the right side of the axle and wiggle the axle out of the front fork legs. Then the wheel can be rolled toward the front of the bike so you can get the discs and carriers off the wheel. It seems to me this is the only way to do the job. Replacing the brake pads would require removal of the front wheel too. Strange... You should hang the calipers from the bike somehow so not to stress the brake lines.

With the front wheel off, using a magic marker, I marked each disc as to where it fit on the carrier. I wanted to replace it in the same location as it was before. I did one at a time so I wouldn't get confused. Also you want to make sure you put the disc back on the same side from which you removed it. I removed the 8 Allen head screws on each side, which freed the disc brake carrier from the front wheel. You will want to be careful removing these screws as they are soft. Make sure your Allen wrench is in good shape and you get it all the way into the screw. I ruined one trying to remove it. You could use some grinding compound or something like that to get a good bite on the screw. I ended up replacing all 16 of these screws and the accompanying washer. Another $56.00 for some cosmetics more than anything else.

Now you have the disc brake carrier and the disc. I did mine on the kitchen table with a towel under it. Did not want the SWMBO to get too mad. The rollers are attached on the back side with a Circlip. It is hard to describe what it looks like. Generally, it is a "C" with three points on it that spring over the groove in the roller. Under the circlip between the disc and the carrier is a tension washer. It is a circle but won't lie flat on the table if you can figure that out.

To remove the circlip I used a small punch and a rubber mallet. First you must get a screwdriver and pry the circlip away from the roller. I used one that had a blade that was about 3/32 of an inch wide. You kind of have to dig it in then twist it to get the circlip away from the roller. Once you get some clearance you can take the punch, place it on the inside diameter of the circlip and tap the circlip out of the groove in the roller. Once you get the hang of it you'll be set.

As I took each of the circlips off I tapped the roller out of the hole. There are a total of 12 rollers on each side. 9 of the 34-11-2310-086 and three of the 34-11-2310-995 rollers. The latter have a snap ring in them to act as a spacer and hold the disc tightly to the carrier.

On my bike these were very worn. In fact, some of the snap rings were half gone. You may find that it is hard to get them out of the holes. Just whack away and they come out.

Now you have all the rollers out of the carrier. Again, be sure to mark the rotor and carrier so they go back together the same way. I put a dot on the carrier near one of the screws that hold the carrier to the wheel. Then I put another dot on the rotor opposite the first dot. The carrier and rotor can be inspected. I cleaned mine up a little with some wax etc. Just be sure you mark them so they go back together the same way. (It might be a better idea to replace the rollers as you go. Just be sure to mark where you start and where the snap-ring rollers go.)

Start replacing the rollers by using one without the snap ring. It is easier to put the non-snap ring type together. Every fourth roller is one with the snap ring. So there are three per side. I marked the holes where the snap rings were going to go. Once you get them in you can't tell which type it is, so be smart and mark them first so there is no confusion afterwards. DAMHIK.

Put the roller in the hole, hat brim to the outside, flip the rotor over while holding the roller with one finger, put the washer on, and then slide the circlip into the groove in the roller. Lay it flat on the towel and use the punch and rubber mallet to gently tap it home. Once you do it a few times it is easy.

The snap ring rollers are a little more difficult. The tensioning spring has to be pushed into the groove in the roller for the entire assembly to fit into the hole. The snap ring is not a complete circle it is about _ of it. In other words a circle with a chunk cut out of it. Its diameter is larger than the diameter of the roller. That is what provides the tension.

What I did was this: Set the rotor up on its edge, take the roller with the snap ring and move the snap ring so the open end is facing up. The roller looks like a top hat. There is a groove for the circlip at the end away from the brim. The groove for the snap ring is in the middle of the hat, about half way from the brim to the top. Push the snap ring into the groove at the midpoint between the top and bottom Then by tilting the roller slightly so that the snap ring at the back of the roller is wedged into the hole in the rotor, push the roller into the rotor. This will give you some tension at the back side of the snap ring. Gently lay the assembly down with your finger holding the roller from the top side of the rotor. Then take a small screwdriver and push the snap ring into the groove at about the mid point of each side working toward the open ends of the snap. All the time pushing down on the brim of the top hat to maintain some tension. Otherwise the snap ring will pop out. Once you do one you will get the hang of it. Be patient!!!!!! Then flip it over and put the washer and circlip on.

Installation is the reverse of the removal. I put the carriers back on the wheel. Having marked them it was easy to make sure they were in the same spot. Once I had the carriers on the I remounted the wheel. This was a PITA. I took some plywood and shoved it under the wheel so I could maneuver it. Then I had to jiggle the calipers to get them over the rotors. The disc brake pads flop around inside the calipers so I had to use a screwdriver to separate them so they'd fit over the rotors.

Once the calipers were over the rotors I shoved the wheel backwards until finally, I got the wheel in the right position to reinsert the front axle. I put a little all-purpose grease on the axle and did the reinsertion thing. The axle goes in most of the way by you jiggling it back and forth with the screwdriver or drift. Mine kind of hung up a little right at the end. I bipped it with a rubber hammer and it went the rest of the way in. Using Clymer's recommendations and torque tables I buttoned everything back up. Like everything else you can do it a lot faster the second time around. A torque wrench is essential to this. Some of the screws are very soft and can be easily damaged by over tightening. Be careful not to overtighten the screws that hold the carrier to the wheel.

The discs are really tight now, almost no perceptible movement. I ran the bike around the block, got no ABS faults, rattles, clunks etc and it stopped just like before.

Thanks to Bill Boyd and Paul Glaves of the IBMWR list who supplied part numbers and some coaching along the way.

Addendum 1 added November 2001.
Addendum 2 added August 2005.

 

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