GT PP Brake Judder from high speed... HELP.!

[Bridgie]

Brake Question for aficionados on my 2015 GT PP (Brembo's)

After winter replacing rotors and pads (Carbotech XP12 - Pre-bed) I am getting a judder at around 40mph when heavy braking from highway speeds. Which then disappears at stop or when the car slows further. Normal brake bite is resumed.

I have ran the car hard, making a second bedding of the pads - No change
It has been driven normal round town, making no improvement.

Is it possible to get any air in the ABS system..? Faulty wheel sensor.? Worth a Vac of reservoir from the top.?

I am on track in 2 weeks and a little concerned with this issue. No Glazing or grooving on the rotors, no visible deposits either. They have gotten HOT during spirited driving, which should have cleared normal bed issues.
After multiple changes of pads and rotors over the years and even full seal rebuild - I have never had this issue..

Any Ideas, suggestions are welcome..!
Dave

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[Ewheels]

The only times I have experienced brake judder was when:
1) I had super cheap rotors on the car and they hot-spotted horribly
2) I hadn't efficiently sanded down my rotors and switched pad brands. Had multiple compounds on the rotors which caused the same feeling. Though this isn't as prevalent on more aggressive pads.

With that said, what rotors are you using and have you recently switched pad compounds?

 

[AZlb5.0]

Shuttering comes down to rotors or pads. Air in lines will make your break pedal feel either really spongy or hard. With that said, if you keep driving like is, and it turns out to be the pads, (more then likely) you’re going to have to either turn the rotors or get new ones depending on what the pads have done to it thus far.

 

[Bridgie]

Everything is brand new - Centric rotors from Rock Auto (Throw aways) Carbotech XP12 Pads
The pedal is firm, no fade or softening, not even covered 500 miles on them yet.!

I have repeated these exact parts from 2 years on previous installs.
That is why I'm stumped.

 

[Emilbadal]

You also may want to check your wheels not to be bent or warped. Or if you have aftermarket wheels to have your hub centering rings on.

 

[Bridgie]

You also may want to check your wheels not to be bent or warped. Or if you have aftermarket wheels to have your hub centering rings on.

I have hubcentric aftermarket wheels, I’ve not tried the race slicks yet. I did a tire rotation last weekend without success.

 

[Emilbadal]

Tire rotation wouldn't do much if one of your wheel is out of true. Basically shifting where the vibration occurs. I'm not insisting on this at all, it's just something to double check.

 

[Bridgie]

Update: after a weekend at VIR, setting my first sub 2:10 laps..!
I decided to take the car to the track after further bleeds of system and complete spare front rotor and pad set just in case.
Brake vibration / judder still there , then experienced some soft pedal intermittently around the track, but in heavy braking all was good,.

Once home and a day of clean up, I lifted the car on my new quick Jacks.
Then found the drivers front wheel was wobbling around as though the wheel bearing was fooked. Wheel off, cover off.. then see my hub nut had backed off about a turn and could be finger tightened.. there was no noise, evidence or feel of a wheel bearing going. Hub nut tightened and a test drive. The feel is back to normal, brake vibration gone and a few trips to work these last days shows no issue.
I was experiencing some brake Knock-back due to the hub moving, which caused the soft pedal and am amazed the hub stood up over the weekend, especially fully loaded at speed through Hog-pen.

A lesson to us all, if you feel it, fix it..

All hub nuts have alignment marks and I constantly check the rears, but having the covers on the front hub took the focus away. All will change in the future as a pre track check.!!

edit: A new hub is on order…

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