Vibration when hard on brakes

[Install425]

This has happen few times, yesterday it was pretty bad. I took a friend for a ride, got going pretty fast and hit the brakes hard and a vibration / grinding (not so much grinding) noise was heard from the front end I let up off the brakes and reapply and it's less. Under normal braking it seems to be fine. Any thoughts I'm going to take a look this weekend.

[Brother]

Sounds like either a warped rotor or worn suspension bushings. Neither problem is safe to drive with. Drive slowly to a good shop or fix them soon.

[JeremyD]

Or a loose caliper. slow down until you can check it out

[Paulporsche]

As above, or maybe you are down to the wear limit on your rotors or pads = time to replace.

Or, if you don't drive much, it might just be rust on the rotors.

Check also your wheel bearings & suspension.

[scottb]

Sounds like warped rotors and/or worn pads.

[Bill Verburg]

Infuences on brake judder:

* worn bearings
*worn struts
* disk quality, tolerances on the dimensions, material specifications, casting and residual stresses.
* Quality of the pads, the higher friction coefficient makes the car more judder sensitive.
* Some pad/disk combination can create friction material debris on the disk, this can also create judder.
* Disk and caliper aligning, the disc should not have more axial play as 0.1 mm.
* Larger wheels (heavy) increase the judder sensitivity.
* The lighter caliper makes the car more judder sensitive.
* The resonance frequency of the suspension/wheel layout is a great factor in judder sensitivity.
* Changing to larger/smaller Calipers, sometimes Spacers and longer Studs are needed to change the above characteristics. Of course if you stay w/ stock brakes Porsche has already done the hard work

[Deschodt]

REad this: No such thing as a warped rotor apparently

http://www.stoptech.com/whitepapers/warped_rotors_myth.htm

But regardless, yes, that is the problem. Replace the discs and pads...

[Install425]

Thanks for all the response. I decided to replace rotors and pad, rotors did look at bit worn and groved.

Checked bearings all looked good, cleaned, repacked and reinstalled.

I did see on drivers side the tire has been rubbing a bit on the washer fluid tank and top corner of front bumper.

I do have 18" rims, a little tight. Thanks again

[Install425]

Here is another cool brake picture.

[Install425]

Does anyone know how tight the nut under the hub dust cap( the nut with the 6mm allen bolt)? I thought I read 11 ft lb. but I dont have a tool or better said don't know how I would measure the the torque value for this. Sorry if this is a little confusing.

[Install425]

I ask because the whole hub / rotor assemble spins nice and smooth but seems a little tight. It spins but lows fast?