For a while now I've been getting an intermittent "clunk" -- sounds like a heavy solenoid, feels like heavy metal smacking heavy metal, can feel it through the brake pedal -- when releasing. Like *exactly* when I release the pedal.

Definitely coming from the front end of the vehicle, sounds a bit to me like it is coming from vehicle center. Sometimes louder than others. Sometimes sounds more left than right.

Can't reproduce it at will, but tends to happen on turns, especially in reverse (backing out of garage, for example).

I have removed and re-lubricated all contact points on all four front brake pads and it made no difference. Didn't improve it, didn't get worse. Stayed the same. Pad wear is dead even on all four pads, so definitely doesn't look like the calipers are sticking on the slide pins. Bled the brakes earlier in the year as part of routine maintenance, had zero impact on the behavior. Replaced the *rear* pads earlier in the year, again as part of routine maintenance, had zero impact on the behavior.

My guess is that this is benign, but not being able to figure out what it is is driving me bats.

Last detail -- it *may* have started when I got the calipers painted -- but I'm not sure of that, have never been able to fix the start date. And if it isn't the pads clunking, I dunno. And the correlation to having the wheels turned (or maybe when actively turning the wheels?) baffles me.

Anyone ever dealt with this?

 

Strange. I know that these cars often have the top mount issue that creates noise on low speed turns. It's very strange it happens on releasing the brake though. My initial thought would be stuck pins but you said you checked that already.

 

Yeah, definitely not stuck pins. Even if my check was no good, with many miles as I have put on the pads at this point, stuck pins would cause uneven wear and my wear is pitch-perfect.

But I think I found the answer. Side-to-side movement of one or more pads, meaning the pad moving in parallel with the rotor, not perpendicular. The "clunk" is from the pad ear banging the mounting bracket (at whichever ear, depending on direction of wheel rotation, and the "bang" occurs when the rotation direction changes).

Check out this YouTube. Brakes are Audi/VW but the physical pad/caliper setup is pretty much identical to the fronts on my F56S. The sound in this vid is also a dead match.


I haven't pulled the wheels off to verify, but if this is the issue, the solution is to bend the metal tabs on the pad ears to provide a more secure side-to-side fit / eliminate the side to side movement. Shims of some kind could also resolve it, but on general principle I would prefer not to add more physical parts to the brake setup.

If this is the issue, the timing with my calipers getting painted may also be explainable -- they had to pull the pads off to do that work, and if the tabs were bent during removal or reinstall -- even a little bit -- in a way that allowed more play, well, there you go.

 

Yep a loose pad will definitely do it.

 

I had my F-56 clunk twice going into reverse. It can't be replicated yes, but it sounds to me like axle CV-joints or axle-related. Does it happen when you shift from Park to Reverse ? ?

 

Confirmed that all four front pads had exactly the same kind of free play shown on the Audi in the YouTube video I posted upthread. No question at all. Flipped the calipers up, and was able to slide the pads side to side, bonking them around without any difficulty or really any effort at all. And they made a nice solid "clunk" at each contact.

Bent the springs/clips on the pads to get them firmly into place and eliminate the side-to-side free play.

Whether that will be enough to eliminate the problem I don't know, but I will definitely look out for this side-to-side-slide play when installing new pads in the future.

 

let us know how it goes and if it fixed the issue

 

Will do

 

Quick update. I have only taken one good ridearound thus far, so not ready to say yet that the weirdness of the problem is gone.

I *have* run into the sound again while basically going from rolling forward into a parking spot, to stopping, to backing up in a mostly-straight line (clunk), to going forward again in a mostly-straight line (clunk again).

I did not run into the sound again on any turns, whether forward or reverse.

I suspect from this and prior experience that this is pretty much about slow movement with the brake applied -- which makes a certain sense, the rotor dragging the pads along for a "rotational ride," and I suspect that that is somewhat to be expected in a straight line. Under normal driving speeds I would expect this not to be as much of an issue, due to increased force on the pads from the piston/caliper needed to stop. And as the video pretty much shows, if you have pads that fit nicely in the bracket in the first place, not so much of an issue to worry about.

I'll report back other findings when I have them. But comparing this setup to my not-MINI not-Eurocar, what sticks out is that there are no pad shims -- and pad shims would easily resolve this issue (either that or just make the pads long enough so they don't bang around like this in the first place...)

More to come

 

Final report: better but not 100% resolved, and I don't think it's going to be 100% resolved.

First thing: I don't know who manufactured my front pads. They are probably genuine BMW, but they were on the car when I bought it so, not known.

Second thing: again pointing back to the YouTube video posted upthread, my MINI looks like it has those same caliper assemblies (TRW) and it has exactly the same side-to-side pad play the video documents.

With item #2 in particular in mind, alongside the strong lateral forces on the pad whenever you apply the brake, the shims would have to be ridiculously strong -- like arm-wrestling strong at least -- to hold strong against those forces. Well, I can bend the shims with a pair of pliers and without arm-wrestling application of force. So I expected some play would return, the only question being how much.

Some play has in fact returned. However, the clunking is now largely limited to going into reverse motion after the pads had last been braked while in forward motion, and is occasional rather than routine. And not really getting it so much on turns now. I would say the frequency is less in general.

I plan to put Akebono pads on when the time comes -- but I'll also be eyeballing that lateral play before buttoning up the install when that day comes, and I will also be looking into stronger shim options (I don't know if they exist, but if they do exist, I'm interested). Obviously won't know if I even need shim options until I try to install new pads, soooo... well, you get the idea.

That's all folks