Jer

Early November I replaced my front pads because the brakes were shaking. The rotors looked good so I left them in. The shaking went down a little, so a few weeks later I replaced the rotors. I was only able to remove the left caliper; the bolts on the right caliper were seized, and the sun was going down so my time was running out. I was able to remove the caliper today and install the new rotor. Now the brakes pulsate awfully (I can feel the brake pedal being pushed back on my foot). I spun the rotor and looked at it in relation to the pads, and theres a change in distance (very small) between the two at certain positions. I'm assuming this is what's causing the pulsation. My question is will the pads wear themselves down so they'll properly contact the rotor at all points in the rotor's revolutions? Or will I have to replace the pads AGAIN.

Arnie

If the distance between the rotor and the pad changes as you spin the rotor, that means that the rotor is warped, right? It could be defective, even though it's new. Do you have those so-called "klean wheels" inside you rims?

Jer

It was my guess, too, that the brand new rotor was warped. I don't have "kleen wheels." I guess I should attempt to exchange those rotors for new ones (at no cost to me, of course).

Jim's500E

How are your brakes lines? Any kink in them can cause the pulsating too...been thru that in my old 190E 2.6 once.

bamberger_1

Hi Jer,
the pulsations can also be caused by dirt or rust in between the hub and the new disks. When exchange them you need to very, very carefully clean the hub faces and the new rotors (inside). Also check for burrs around the screw holes. New rotors can only be checked on a lathe not on the hub, since you measure the addition of all failures. If the distance between disk and pad is only fluctuating in one or two spots, it calls for non proper assembly. (did not forget the little Allen screw. to hold the disk??)
An other question is the brake cylinder/piston moving freely?.

Jer

I put the old rotor back on to ease the pain.

The brakes were pulsing a little before this brake job, which is why I did all this in the first place. I'll have to check the hub for dirt, but it looked pretty clean on first inspection. What's odd is why the new rotor is pulsates worse than the old one, when I didn't even mess with the hub between exchanges. I also secured it with the allen screw.

Other than cleaning the hub, any more suggestions...

Arnie

So, do the brakes still pulsate with the old rotors on. If it's significantly better now, then your new rotors were defective, take them back.

Jer

The left side has a new rotor, the right side has the old rotor. I guess I'll have to exchange the rotors.

Jim's500E

Maybe Santa will bring you a set !

(how do caliper piston seals look and did you bleed new fluid thru the lines?)

Jer

The piston seals looked fine at a glance.

I didn't drain any fluid. In fact the brake fluid is pretty old and should be renewed soon.