nishboo

I recently did a brake flush and replaced my brake pads and rotors on my S600. What I noticed is a nice solid stop, however after about 2 months I started to get a vibration when slowing down. It was on the steering wheel and the brake pedal. I went back and they replaced the rotors. It happened again, and so they replaced rotors again. And now a third time!

This time they replaced the pads, and we still have the issue. In between they even suggested to replaced front lower control arms, since they had some wear, however the car only has around 65k miles. We went ahead and did that. Still same issue.

I am completely lost as to what is causing this. Any ideas what it could be? I know everyone is going to tell me its either the pads or rotors, but they have been changed many many times already. Any ideas??

alx

Depending in a lot of factors you just might not be exercising the brakes sufficiently. Try the following- on a suitable section of closed road in Mexico bring rotors up to temp- moderate braking a few times from say 60 to about 30. Then accelerate to 100-120 and threshold brake to about 30. Repeat a few times. Do not come to a complete stop each time.

If that does not solve the issue rotate wheels front to back - you might have a bent wheel/ bad tire on the front that acts up only when pushed hard upon.

One more thing- make sure your calipers are not dragging. If they do they will overheat and bend the offending side rotor. To check - drive on Highway for a bit and coast to a stop (works well when going uphill) without using brakes... You can tap them at the end to come to a complete stop. Get out and check temp of rotors. They need to be cool and all roughly the same temp. A hotter rotor will denote dragging caliper and your culprit for bending rotors.

nishboo

I will give that a try. Thank you!

I dont think I can rotate the wheels front to back because they are staggered.

alx

Doesn't matter. Rotate them just for the test. The car will still work just fine and you will have a no cost data point

nishboo

Ok, cool. Good looking out! Thanks!

nishboo

Changed pads and rotors multiple times.. Still experiencing this.. Could it be bearings?

Vibration usually occurs from freeway speed to 35mph, then it goes away. While driving the car is smooth at freeway speeds, but has a vibration that lasts for 1 second, every 4 seconds. Its weird... Thoughts?

rsr911

Ditto have the same issue with my 2008 4matic. Have rebalanced new wheels and tires. Have had my shop check the brakes which were replaced only a few months ago.

Only happens at highway speeds, and fades away around 35 mph. Never happens if I keep below 50 mph.
We are stumped.

shadenfroh

I assume you've gotten a complete brake service (with fluid and cleaning) which means your brakes are operating 100% correctly, not dragging or anything. As for tires/wheels - a reputable shop will tell you if you have a bad one in 5 minutes.

Your problem sounds like unevenly worn rotors. Big reason for this are lazy mechanics who just put the wheels on and slam them tight with the air gun nut by nut. This way the assembly is not properly seated and you get uneven wear.

Do this - insist to see the readings on the rotor thickness gauge yourself and write them down. Basically they hook the gauge on something steady (control arm), position it over the rotor, rotate the rotor and check for thickness across. Ask for the acceptable deviation in thickness.

When you go home - jack up the car, loosen lug nuts, tighten again using star pattern. Do this on all wheels.

Source: been there, done that.

alx

If the surface of the hub is brushed clean from rust and the little fixing screw for the rotor is installed and tightened properly- how you tighten the wheel is largely irrelevant. The rotor sits flat in the hub and good luck twisting/ wedging it against the hub...

If brakes and tires are good next I will check control arm bushings.

rsr911

UPDATE: I have been battling this issue for months and months. When my S550 went in for a B service we reset and recalibrated the ABS brake system. Vibration problem is greatly reduced.

We believe the rotor drying system was dragging the pads too much and overheating the rotors at highway speeds causing them to warp slightly. Then when brakes are applied the ABS could not figure out what to do.

I still have slight warping of the rotors due to long time issue but the severe vibration has greatly reduced due to resetting the ABS. The pads don't drag and overall braking is much more responsive.

alx

lol... you didnt smell it? usually when that happens there is a strong brake pad smell... and smoke sometimes... as well as premature pad wear...

rsr911

No it is very light pad contact. Just enough to create extra heat. I drive mostly in town so I was only experiencing when I went on trips.
Was driving me nuts. No vibration at low speeds braking.