Head-scratcher here.

Had steering wheel judder under braking last year. Replaced all four rotors and new pads all around. Good stuff, too -- Zcoats.

That cured the problem...for about 1,000 miles. The problem has been creeping back the last month and is now back to where it was 1,000 miles and a complete brake change ago.

Went out and did some power stops this morning. Made things worse. Pretty sure it is warped rotors as the juddger only occurs under breaking and when I slow for a stop light, the ... car ...... grabs ............ to .....................a.............................stop at.......................................................decreasingly longer............................................grabs until car stops.

Why am I frying rotors?

Bad caliper? Hub?

Am hoping my next set of rotors lasts, say, 20,000 miles.

 

my guess will be sticking caliper

 

Sliding plates in caliper wrapped due to aluminum oxidation, causing one sided contact with the brake disc.

 

Also possible just uneven deposits of brake pad on rotors.

What pads do you use? Were the new pads/rotors bed in properly?

Marc

 

^ +1

Good reading here on the notion that they're not exactly warped, but deposited...
http://www.stoptech.com/technical-su...nd-other-myths

 

I'm having the same problem and I think it's stuck calipers. I'm going to have mine rebuilt and we'll see what happens.

 

Marc: Textar pads.
Was hoping it was deposits but I just did eight to ten 60mph to 20mph stops. Got worse.
Caliper check time, I guess.
Thanks all.

 

I used Textar for many years and I always ended up with a slight jutter caused by deposit build up. After a track day it was a sure thing.
I then bought cheap Sebro discs and more expensive StopTech race pads for the front and EBC race pads for the rear. 15 rounds on Nurburgring and 4 trackdays on smaller tracks I have still no jutter. One trackday I had smoke from the brakes, but they also survived that. Racepads are harder on the discs, but with cheap discs and no jutter I can live with that.

 

Update from original poster:
Finally took my car into my indie in KC: Rennsport KC. I figured the front caliper(s) would need to be rebuilt.
Mechanic -- Karl the Porsche Doc -- found soft brake line had collapsed. The left front caliper was not getting fluid. He put new lines in, turned the rotors and problem fixed!

 

Do you know the age of the lines? OEM or aftermarket? When was the last time they were replaced?

 

Not sure about age or make or but will check on Monday.
Here is link to Karl's blog. It is first rate. He talks about the procedure he performed with great pics.

http://rennsportkc.com/blog/

 

When my old Audi failed it's MOT around 10 years old, the lines had ballooned, the tester reckons this happens a lot......when I saw them with the brake pedal being pumped I couldn't believe it, they felt fine on the road......its just we never get to see them under load....
After that I always replaced mine every 7-8 years or so on all our cars, just to be safe.

Kevin

 

I replaced my rotors with cross drilled Zimmerman"s a year ago. They were fine until I had new tires installed and an alignment done. Could the tire shop over tighntening my lugs with a impact caused my rotors to warp?

 

Hey Greg,

Yes, over torquing the lug nuts can cause the rotors to warp. While typically we don't see this on street cars though (i've seen it on maybe one or two cars in the last couple years), but on race cars where guys are in a hurry and just zip their lug nuts on with a gun (ironic on a track eh). The added abuse on the track gets the rotors hot enough to be affected by the uneven torque. Always insist a torque wrench is used at 96ft/lbs, or at bear minimum a impact gun with a 100ft/lb torque stick which will prevent over torquing.

 

Had the same thing... One day could be worse than another.

Had the original P rotors resurffaced... Probem came back inn 1k miles. Then replaced rotors and pads (sebro and textar) again 1k miles later it was back. Then had them resurfaced with a pro-cut according to P standards.

Problem solved 8k mi later it's still fine.

I think the slightest imperfection on a rotor causes it to get worse and worse. And one type of resurfacing isn't the same as another.