gator9_911

Rookie GT3 question.....still learning the car after 5 months.

Just installed new PFC 08 pads all around. New Pads...old discs. Under sudden or "brushing" of the brakes...the front end shimmies in my hand. I will hear a slight squeal/whistle as I started to brake...and then the shimmy in the front end. If I jumped on the brakes...the wheel would literally jump to one side. In hard brake zones (145 -> 70mph) the car had plenty of brake...but would move around/shift in the front end. Enough to make sure you are wide awake and paying attention.

I previously ran Pagid Black pads all around. Is this normal? I have read a lot about having to brake the old discs in with the new rotors as they make their "mark". It did get a little better when I went easier on the brakes. These pads bite a lot more up top then my old ones and I had to actually back down the pressure.

Any suggestions or lessons learned would be great. Thanks!

PointBy

Sounds like you may have developed a bit of brake judder. Judder is, simply put, uneven pad deposits that cause a slip-grab brake sensation or "shimmie" as you call it. It can be caused by a number of factors such as swapping between incompatible compounds on the same discs or improper or incomplete bedding of new pads.

996FLT6

Just do a trackday- it'll be all gone : ). Mike

gator9_911

Slip grab and judder are perfect descriptors. Please tell me there is a fix......

Thank you

gator9_911

This past Friday was the first day on the new pads.....and the first time I felt this happen. I thought it would "burn off" but it was still doing do it at the end of the day.

paver

I have some discs that have judder. Haven't tried it yet, but I have been told that slow speed street driving for a while will take care of it. About bedding them in, I always hear that PFC 08 doesn't need bedding...whatever that's worth. Hope you get 'em fixed.

85Gold

Gator

Did you ever check the inside of your rotors for a crack, I know it's a long shot but do eliminate that possibility.

Peter aka The Farmer

Burger

I've had pad shimmy and I've never found any amount of track driving or street driving will get rid of it. If you went to a really aggressive compound, maybe.

What happens is when you use the brakes, some of the material from the hot brakes transfers to the rotor. You end up with the same material on the rotor and the pad, which works well together. When you switch to a different pad compound, the old compound is still on the rotor. The two compounds don't always play nice together and you get the shimmy.

Here is a set of rotors I was removing the Hawk DTC70 compound from because it was not working with the PFC06s I put on.



Removing the compound from the rotor was not an easy task. It would have been better to replace the rotors.

If you take your rotors to a machine shop, you might be able to get them to turn them just enough to remove the compound layer. Don't let them use a brake lathe on drilled or slotted rotors, it could be bad.

997gt3north

^^^^^^^^^^^ --- this

- years ago i tried some PF-01s on an older car when I was using Pagid Oranges
- it was a total and complete nightmare
- car instantly got the 'judder' as mentioned above
- then only way to make it palatable was to stand the car on its nose into every corner with full 100% braking otherwise it was terrible
- i never used those pads again
- i think PF pads only like 'new' rotors - that's what I have concluded - at least in my experience they don't like pagid pad 'seconds'

bobsan

Concur with all above, PF not liking previous pad embedded on rotor, try giving it large on track until pads are smoking (literally).

PointBy

There is a fix for judder. Step one is to remove the old judder pad material from the discs. You could machine the discs or use a cold race pad. Most people recommend to use Hawk Blue, which is an aggressive race pad, If you brake gently at low speeds while those pads are cold they will strip off the old pad material... and some of the disc. Once the judder is completely gone, swap back in the pads you want to run and bed them in according to the mfr's instructions.

Other methods may work, but are not generally reliable.

gator9_911

Thank you for the advice. I already checked to make sure my rotors are not cracked....so it's clear this is old pad material.
Thanks for all the help. Very appreciated.

gator9_911

Going to Sebring next weekend. Will attempt to burn off pagid material using the old fashioned way. Max brake!

85Gold

See you there Sunday but I will be in the M3 not the GT3 from RR.

TrackDays247.com

Check surface carefully for deposits - switch back to PAGID LOL LOL :-)