Weird brakes issue

[curtisnj]

We put the 84 528e on the road. It sops straight, but I don't think the rear brakes are working. Here are the facts:

1. rear discs shiney on only 3/4 inch on outer surface
2. pulled wheel, piston is moving with brake pressure
3. new pads
4. fronts discs flat and shiny
5 Both rear discs identical wear.
6. riding pins perfectly lubed and smooth.
7. car has 100 miles on pads

Questions:

Does master cylinder address rear brakes independent of front?

Any advice? Curtis.

[C.R. Krieger]

We put the 84 528e on the road. It sops straight, but I don't think the rear brakes are working. Here are the facts:

1. rear discs shiney on only 3/4 inch on outer surface

5 Both rear discs identical wear.

7. car has 100 miles on pads

Either your rear disks are dished or the pads aren't seated properly. Since I doubt you could improperly seat two sets of pads at the same time, I would suspect the disks. If the middle is rusted, there is no way you'll fix this with new pads since the rust is actually harder than the pad material. It will cut it away, thus allowing even more rust to form. The only fix is to change disks. Then, drive it vigorously to get the pads worn in to match them. Don't allow more rust to form (other than overnight, which is normal - but get them warm to get the moisture off the next day) or you'll be changing them again.

[curtisnj]

These pads are new. are there supposed to be shims? I'll betcha both pads are not sitting right. Any thoughts?

[C.R. Krieger]

These pads are new. are there supposed to be shims? I'll betcha both pads are not sitting right. Any thoughts?

... and I'll betcha they aren't. No, there are no shims and I already said it was unlikely you got them both in wrong. If you don't really plan to give serious consideration to the answers you get, why ask?

[curtisnj]

The reason you ask, analyze and consider is that there are many different inputs to consider. I do put weight on answers, but I also consider different points of view. I am a logical thinker, and as a result of that, I know that is more likely that I made a mistake than two unrelated parts failed identically. It is this logic that, through BMW colleagues as well as forums, that I draw cautious conclusions. Also, I have done many brake jobs, and this is the first time I have seen this unique pattern. Therefore, I take no absolute answer. Take a look at various threads. It is the voluminous number of answers that lead to the correct solution. Also, my implication was that I bought the wrong pads, not that I seated them wrong.

I will post the correct solution when I find it. Curtis

[KWood86-E28-535i]

Same thing was happening to me a few months ago. I took all four rotors to my local machine shop and had them all turned down. Then put new pads on and havent had a problem since. My old pads where fine (enough pad left) but not flat and since I was taking them off I thought it was a good idea to put new ones on.

[Brad D.]

Were the rear rotors new or turned? If not, I would be C.R. is right.

[curtisnj]

The rotors need to be turned. C.R. was right. I tore into it again last night, and the rust is just onite rust.

Thanks for the on line and off line input.

Curtis.

[C.R. Krieger]

The rotors need to be turned. C.R. was right. I tore into it again last night, and the rust is just onite rust.

Thanks for the on line and off line input.

Well, if you can stand a little more input ... don't bother turning old E28 rotors. They're cheap. Buy new ones.

[curtisnj]

Thanks. I appreciate all input. Curtis.