Hi all.

My X-type developed a vibration/shimmy while braking. It felt like it was coming from the front, so I inspected both front brakes without finding any problems. My thought then was some problems with the ABS. But when I tried applying light hand brake while driving, the shimmy was still present and it had to come from the rear.
Found a defect like a missing surface part on the inside of one of the rear discs. Changed disc and pads and problem was gone.

 

Looks like there are other areas where material was about to let go.

Good troubleshooting.

 

oyster, the flaking that you are seeing is due to either poor metal that the disc was made of or the metal started to get too cool to do the casting and in short, part of the skin that forms on top of the metal fell into the casting, creating a spot where the metal did not adhere to itself.

Unfortunately, this is a problem with casting metal pieces and in most cases, this defect would have shown itself a long time ago. But, in your case, it just happen to lay just right.

 

Thank you Thermo.

Looking at the pads, one has got an anti-squeel shim and one does not. Which one goes where. inside versus outside?
It is also a tapered edge on one of the pads. Orientation versus wheel rotation?

 

oyster, honestly, I throw the anti squeal shims away if they come loose. I use a product called "pad glue" (can be bought at a local auto parts store for pretty cheap). This will do the same thing as the shim and makes things easier to deal with when re-assembling things.

As for the pads, if you are putting a new rotor on the car (which I am assuming you are doing), you should really replace the pads at the same time. This is to prevent excessive wear of the rotor due to any grooves in the pad. If you look at the pads, there should be one pad with a post sticking out the back (say 3mm high) where the other will be flat on the back. The flat backed pad goes to the outside, the one with the power goes against the piston of the caliper (falls into a groove on the piston if it is the rear ones).

 

Hi again.

I have changed discs (rotors) on both sides. Also new pads all over. All 4 new pads had the pin that goes into the groove in the piston, so I guess it doesn't matter which pad where as long you make sure you hit the groove.

 

I have a different theory. I think that the disks were heavily rusted and then used. The pads polished the surface of the rust so they looked more or less OK. You can see that effect on the rest of the disk. When steel or iron gets heavily rusted the rust starts to come off in flakes. You can see that in old bridges that have not been maintained. I think that the flake you see is just a rust flake. You can test the theory by banging the "good" areas of the disk with a hammer and a chisel. You should be able to get flakes from the rest of the disk. I suspect that the car sat outside for a long time without being used. Pete.

 

Jagger.

Thanks for your comment. I have had the car since new, and it has been in regular use.
The discs were changed 4 or 5 years ago. I think they were a bad lot.