[SnapCoupe]

Originally Posted by ElevenEleven

I bought a 2009 328xi E90 sedan automatic a few months ago from a friend. It had 103,000 miles on it and seems like it's in great shape. After a few days I started to notice a vibration that starts at 20 mph, and continues to speed up and get louder as I go faster. If I hit the brakes hard, I get a lot of pedal pulsation that has the same frequency as the vibration (womp-womp-womp-... especially noticeable at higher speeds, like 60 mph, but very subtle at low speeds). I've put a thousand miles on the car now, and the vibration is louder and stronger than before.

I've jacked up the car and tugged at the wheels to feel for play, but I couldn't find any play (3 and 9, and 6 and 12 o'clock). I spun the wheels, expecting to feel a warped rotor, but the rotors spun smooth through the pads and the rotor wear looks even. I rubbed the outside of the tires while they were spinning, but didn't find any cupping.

The car has Pirelli run flats on it, and the rears are looking worn. I'm planning on putting on my friend's winter wheels to rule out a bent wheel, or bad tires.

I'll get a dial indicator out and measure rotor run-out this weekend. How much run-out is acceptable? Can .005" run-out cause something like this?

I bought a pair of *** wheel bearings, and I'm ready to install them, but I'm hesitating because the sound/vibration doesn't change when I take a hard left or a hard right, because I didn't feel any play in the wheels, and because I don't think bad bearings could generate this brake pedal pulsation. Do you guys think it's the wheel bearings?

If the run-out is within spec, is there something else that could cause this vibration, and pedal pulsation? I read a thread where E36graduate was saying his vibration happened because the front KW V1 struts were shot. Could a strut do this? How do I check if a strut is toast?

I don't notice the vibration being any different if I'm accelerating, or decelerating. There are no clunks, and no clicking noises.

Thanks for any advice.

Could be your thrust rod/front control arm bushings. To test this, have someone roll the car at about 5mph and then get on the brakes hard. If the bushings are worn you will see the front wheels do a vertical "hop". As the bushings start to go out, they are only noticeable on hard braking, then all braking, then eventually at certain speeds.