PeachParts Mercedes-Benz Forum - View Single Post

pstutcher · #4 06-17-2005, 10:06 AM

Thanks Harry and Blue. I posted this question quite some time ago and received little response.

Here is what I have done so far:

On first noticing the shudder, I assumed that there was a warped rotor and went about getting them off to but cut. After putting them back on with new pads, I saw no change in the condition.

I ordered a new pair of rotors, put them on and again saw no change. Still convinced that the rotors were to blame, I switched the rotors from right to left (only the right side has the problem) and saw no change - so I switched them back how they were.

Investigating further, I made some observations that I find peculiar. When I reassembled both wheels after the final left-to-right switch I had pushed each caliper back a bit to get them onto the rotors such that it left a slight gap between the pads and the rotor surface. Sitting there puzzled, I started turning the rotor and watching it right at the outside pad. I could see the gap change and hear a change in the drag of pad on the rotor moving in and out as I turned it with the "high" spot consistently at the same point on the rotor surface. To be certain the rotor was flat against the hub, I put the lug bolts on (using washers as standoffs) to seat the rotor down all the way. Still the same condition.

Talking with my mechanic and some other people, it was suggested to me that there might be some built up rust on the interior of the rotor mounting surface and/or the outside of the hub. Everyone I talk to agrees with you guys that a warped hub would be very unusual. Knowing that I used new and perfectly rust-free rotors in this whole process, I knew it couldn't be them. So, last night I took it all apart again to specifically inspect and clean the hub mounting surface. Not much there to speak of and again, no change afterwards .

To make sure that I wasn't crazy on all of this, I set up a makeshift mechanism to see if I could measure the runout on the rotor. I used a heavy jackstand and set a point of it right against the high spot that I found on the rotor and turned it again watching the surface move in and out very consistently. Total runout of about 1/16" (eyeball). Same thing with TWO NEW rotors. Very consistent.

While I was in there, I removed the hub and repacked the bearings to make sure there was no play in the bearings.

As you can see, I'm puzzled. The only thing I can think to blame is the hub.

I tried to use the same method to evaluate the runout on the hub mounting surface, but it is so much closer to the center of rotation that it is difficult to see if there is any runout there. I do believe that there is some, but I can't actually see it, only hear a difference in the amount of drag of the jack stand on the surface. Obviously, any small type of movement here would be magnified on the outside of the rotor surface.

Has anyone seen anything like this in the past? I sure could use some help.

Thanks again,

Pete