Arjan B.

Back to wrapped rotors........

I read the Stop Tech article, interesting.

Overhere we machine lots and lots of rotors. As we bring them to the 'machine guy' I wait sometimes for the job, to take them back to the shop. Most of the time on of the two rotors is a bit wrapped.
We did the front rotors of a 993 tip tronic back in May, and renewed the rear ones. Man, there was a real shimmy in one of those.
After machining the problem was solved, and still is, I met the costumer just yesterday.
The inside contact surface of the disk was clean and corrosion free, the wheel hub from the 993 was bright and clean....... So tell me.........

Rocket Rob

I haven't seen anyone mention that you also should check your tires for uneven wear and balance, wheel bearings and tie rod ends. I had a slight shimmy for a while and the problem went away after unmounting the wheels and inspecting them and putting them back on the car. I'm not sure what the real problem was but maybe the wheel had some dirt between the wheel and the rotor.

Arjan B.

Adrian,

You know, if I really brake hard, the wobble is almost gone I remember. So a uneven surface could also e cause of the wobble also. If I brake normal and smooth, it shakes the most, stopping from 120 M/PH till 0 with hard braking is most comfortable.
Strange behavour he??
If you look at the disks, they bright and like mirror.

Arjan B.

Rob, that is mentioned before. But.... I drive momentairy on winter tires, almost brand new. Even with my Cup wheels it does the same.

DJF1

Just my -02's here. When I had severe vibration under heavy braking at high speed, I changed the disks thinking they were warped. Wrong. When I rebuilt the calipers , the symptoms were history.

Adrian

Dear Danny,
Yes callipers are often the problem as I said in my first post. If the pistons are not coming out evenly you get the wobbles.
Ciao,
Adrian
964C4

Arjan B.

I think the calipers could be the cause in my situation. I checked the pistons a few times, but they came out pretty easy, all 4 of them per caliper.

Does Porsche have rebuilt ones? And If yes, how much each?

I saw once on the track the 'spots' on the disks which are shown in the article in one of the replies. In that article they say if those spots are shown, pads don't press 100% well on the whole surface.

Mark in Baltimore

Like forklift/Jim and Joey, I thought I had warped the rotors on my 993 after using Pagid Oranges. I replaced the rotors and, fortunately, kept the old ones, but have yet to use Hawk Blues to clean them off. Because of this issue and the extra $100 cost of pads, I've switched over to the cheaper, more corrosive but just as effective Blues and have yet to warp another Porsche rotor.

In my previous Toyota 4Runner, I know I warped the rotors after first getting the truck. I descended a particularly steep hill and had to stop suddenly at a red light. I left my foot on the brakes while idling and, shortly thereafter, noticed a bad vibration when braking under heavy, descending load situations. The problem got worse as time went on and I eventually replaced the rotors. Voila! Problem solved for the next three years. I learned to keep my foot off of the brakes after spirited driving but, in a 5 speed manual, it's hard to avoid using the brakes to hold you when you're stopped on a hill without shutting the engine off and using first gear to hold the vehicle, which I actually did from time to time. With my automatic Sequoia, I either slide the tranny into neutral or put it in park.

Arjan B.

If holding your foot on the pedal at a traffic light under hot brake conditions, the rotor cool not on that spot and can wrap.
Because of the 80% who cools and the 20% who's not, the rotor could wrap.

Here at Opel {GM } it's a common problem, also with ventilated disks. Especially with cars who have automatic transmission. People hld their pedal to prevent rolling.

Tom W

Hmmm. I have nearly new big red calipers (front and rear) with new rotors (f/r). Nearly new means used for 7 days of DE. I'm using Pagid orange pads.

My breaks started to shudder under hard breaking this last weekend at Laguna Seca (two more great fun days of DE). Hard to me is 100+ mph down to about 40 with threshold braking.

I'll be pulling things apart and looking for potential causes this weekend when I do a Cargraphic oil cooler instal and brake bleed/pad check. I may buy a set of Hawk blue and see if they solve the problem.

forklift

I put my Hawk Blues in this weekend and still had the shudders when I bedded? them in. I drove the RSA to work today and didn't notice any, although I did not brake that hard. I will check it out again, but I think it did the trick. Much cheaper than new rotors! I think I will put my old "warped" ones back on next time and use this trick instead of buying new rotors. I am also going to try Pagid Blacks for the front.

Toon

I had new disks and pads installed 2 months ago and had vibration since a week under mild braking at higher speeds.
Saw this tread and went back to the shop and they saw that the disks that had warped.
So they put on the "disk professor" to machine it and now its OK again !! They took of 0.1 mm on each side.

kris

Old thread but very to the point for me. Vibration started a couple of weeks ago on new Zimmermans and pads which were mounted early August, some 2000 kms ago. especially noticeable at slow braking till stop. A few possibilities are AFAIK
1/ Unbalanced wheels
2/ Calipers not coming out evenly. How can you diagnose this?
3/ Wishbone bushes
4/ Warped rotors (read all the stuff around it, I just call them warped to make it easy)
Anybody else encountered this? I was so proud of my DIY, damn.

Indycam

Hiya Kris
#1 Will vibrate with or without brakes .
#2 If the rotors check out as flat , not needing to be cut , then look at the rebuild of calipers .
#3 Not likely , but check to see if they are loose .
#4 Check to see runout , warpage . Cut if needed .

"I was so proud of my DIY, damn."
Be proud ! I don't see any conection to the repair you did .
If you keep the car for a long time you will need to fix up the brakes many times over the years .

Does the brake pedal vibrate under your foot when slowing down ?
Does the steering wheel shake under braking ?

robbed666

I like Adrian think that the problems could lie eslewhere. Had an BMW M6 with terrible wobble on braking. Changed the rotors 3 times over 2 years. Ok when first changed then the wobble just grew, and grew.
Took the car to an independent specialist. He's first words suspension bushing. Three years later when sold, same discs, no wobble.