Front brake caliper rattle

[Phaedrus]

I read everything I could find here about front brake rattle but can't figure out if this can even be fixed or what the fix would be if it can. I'm to understand that the brake is a floating caliper; its supposed to move up and down on the mount. The annoying racket is worst on a rough surface. Applying the front brake stops the rattle, of course. Thanks in advance for comments.

[Bamboo812]

It is not supposed to move up and down, only pivot, or "swing", on the pin. Do you have the o-ring #2 and spring #4 mounted?

[Phaedrus]

Bamboo812, I don't know. The dealer (Austin, TX) has done the work; they say the rattle is normal. However, I don't remember it being there before. I'll have to take the caliper apart to determine whether the washer and spring are there. I suppose that the presence of the rattle is not necessarily proof positive that these two items are missing? Dealer worked on brakes twice to eliminate drag when wheel was cocked to the right, FYI, they also replaced pads and brake line. I replaced master cylinder which strangely developed a leak after their service. Shite happens, I guess. So, if you know, would removal of these two items be, perhaps, an unsatisfactory way to eliminate the brake drag? Thanks.

[Major Softie]

A nice high temp synthetic brake grease on those sliding components is very helpful for controlling any rattle.

[Phaedrus]

Cheap enough. I guess you mean something like Super Lube Synthetic Grease. Meanwhile, I'll take the caliper apart tomorrow (Hoorah!) per Bamboo812, above, I guess. Or, what is your opinion as to what Bamboo812 says? Everyone loves a quick fix, but I'm after the underlying problem, or, the elimination of such. Not to say that a dram of lube isn't the RX. Thanks!

[Kurt in S.A.]

Not sure where the rattle is coming from. But there is supposed to be a phenolic button that the caliper slides on and it slides on the ledge of the slider...look at the lower right of the slider picture...that ledge is what I'm talking about. There isn't a part number for it, but it's important that it be there and that it be a relatively tight fight. Otherwise, the caliper moves up and down between the two ledges, thus creating a clunk, maybe more than a rattle.

http://www.realoem.com/bmw/showparts.do ... g=34&fg=11

I can't find any info just now as to how to replace this part or what to use.

Kurt in S.A.

[Bamboo812]

Kurt is right, there are two black plastic looking "buttons" about 5/16" diameter on the top and bottom of the caliper where it slides. Not listed as a separate part on the fiche... You should be able to see them with a flashlight. Without them, you would see metal on metal wear between the slider the caliper body itself.

[Phaedrus]

The caliper's movement up and down (in line with the slider) is virtually nonexistent but the caliper does rotate on the axis of the mounting/adjusting eccentric pin. A test ride over rough roads results in zero rattle. Further testing at speed indicates the front brake is working properly. Full application of front brake from about 70 mph causes the front end to dive and stops the bike as good as it ever has.

I can attribute the repair to a change in adjustment of the eccentric adjuster. The only other thing I did was refresh the grease, per Major Softie.

Removed caliper. Observed black nipples on top and bottom at rear of caliper, per Bamboo812.

See here: http://s644.photobucket.com/user/jhinds ... sort=3&o=4

These items impinge on these two flanges of the slider.

Top: http://s644.photobucket.com/user/jhinds ... sort=3&o=2

Bottom: http://s644.photobucket.com/user/jhinds ... sort=3&o=3

The spring mentioned above by Bamboo812 is present. The 0-ring washer he mentioned (no. 2 in the drawing) is not present. Please let me know if this ring is supposed to fit on the tip of the adjuster. I looked in the seat in the upper housing for the eccentric adjuster but didn't see it there either. There is an 0-ring installed on the bottom of the eccentric adjusting pin as you can see

Here: http://s644.photobucket.com/user/jhinds ... sort=3&o=1

Adjusting the eccentric is very difficult with a screwdriver, even a very large one, at least it was for me. So I used a bolt that screws into the bottom of the pin except on removal the pin would turn because the bolt bottomed out and got too tight. To remedy this I got a shorter bolt placed a nut on the end and a flat washer then screwed this into the adjusting pin with only enough threading to rotate the adjusting pin. When I got the inner brake pad fitted precisely to the rotor I loosened the bolt without moving the adjusting pin. You can see this "tool"

Here: http://s644.photobucket.com/user/jhinds ... sort=3&o=1

Thank you for your help.

[Bamboo812]

The o-ring is in the correct spot in this photo. The fiche can be a bit confusing.

[Phaedrus]

Bamboo812, Thanks for the clarification.