philpilot

While driving over 75mph on the interstate today I noticed a light shimmy when I applied the brakes. I've experienced no brake shimmies at lower speed. The front brakes and rotors have 30,000 miles of wear and appear to be in good shape. Any suggestions would be helpful.

ibdavid

Rotors are warped.

lowbee

David is right time for new rotors

snaphappy

30k for brakes isn't bad. If you're going to do it yourself feel free to ask questions. I just did all four corners. It was my first Porsche brake job. Not hard, just time consuming with all the extra little parts, for example dampers

philpilot

Thanks for the reply/ I noticed on the 4 year old invoice that no dampers were installed. Just rotors some spring clips and brake pads. Could the vibration be caused because the dampers were not installed? What are all the extra little parts I'd need to do the job.

qikqbn

some times with a little clean up you can reuse the old dampers. Maybe that is the case for you. Dampers are for squealing, not for vibrations. 99% it is warped rotors. That would be my first guest and probably least expensive part. I did chase a vibration under braking situation on one of my cars that was still there after replacing the rotors. I tried replacing my track and lower control arms. The rubber bushings can crack and get loose. Although it improved, the vibration was still there. In my case in the end it turned out to be worn out wheel bearings.

Start with the rotors.

philpilot

I'll do the wheel bearing test 1st to rule that out. As per the records, a new front left wheel bearing was installed a few years back.

OKB

replace rotors

BucketList

Does it only shimmy when you first touch the brakes but becomes smooth when you apply more pressure? If so, it's not the rotors because they will still cause judder when braking harder and you will feel it in the pedal.

philpilot

good ? I'll check it out tomorrow and let u know. If the shimmy stops what are some other causes?

BucketList

Mine shimmies just barely at freeway speeds just as I touch the brakes. It has new rotors and pads up front. For now I am not going to worry about it. Its probably due to the previous owner not bedding the pads. If it gets worse, I will look at bedding or wheel bearings. There are other possible reasons like suspension bushings, but those are much lower possibilities.

Edit - I haven't had the car aligned yet and that is also a possibility. If there is not enough toe up front, the wheels might get twitchy under light braking, but I am just making an educated guess on this.

philpilot

Road tested the car today. Only had the steering wheel shimmy and no brake pulsating. My guess is this is just the start of rotor warping and will escalate to brake pedal pulsating. My last resort is to turn the front wheels on the hub 180 degrees to see if that solves the problem.