Edcantera

Hi guys! I spend most of my time in the 997 forum but am hoping someone here can help out. I’m going to cross post this over there as well as the GT page just to see if anyone has experienced this issue.

A friend of mine with a 997.2 Turbo PDk is chasing a noise he gets when he runs Hawk pads on his car but not when running Pagid yellows. The rotors on his car appear to be 2 piece AP rotors but I’d have to pull the wheel again to confirm. They came with the car front and rear with Pagid yellows all the way around.

The Pagid squeal when cold so he ordered a set of Hawk ceramics and this is the noise he gets:


when running the Pagid pads it sounds like this:


He's about to abandon these rotors and go with Sebro slotted so he can get rid of the noise and run the hawks. We considered the possibility of a slight warp in the rotor but he has no pulsation under braking with either pad. Just the one noise, or the other.

@JRitt@essex do you have any insight?

EVOMMM

His best bet is to call a brake specialist that sells parts
to me it sounds like the pads weren’t bedded in correctly

JRitt@essex

That noise is the sound of the pads interacting with the slots on the disc face. These types of noises are typically dictated by several factors, and are not necessarily disc-specific. If your friend switches to any type of drilled or slotted discs, he will likely experience a similar result. Below are some of the common causes of noises like those in the video:

1. Aging caliper seals- How old are the caliper piston seals, and how much track abuse have they taken? The piston seals act like a little swing gate. A caliper piston sliding out to the left would distort the seal in the manner below (the slashes are the seals on either side of the piston):/
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As the piston slides back in to the right, the seal does this:
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/

There is a certain amount of tension or friction that needs to be overcome before the piston actually starts moving through the seal ring. As caliper piston seals age and see a lot of high-heat track time, they get stiffer and less pliable. When that occurs, the pistons do not retract as cleanly and leave the pads closer to the disc face. The leading edges of the pad then make contact with the disc slots, creating noises like those in the video.

2. Pad shape design/chamfers- Do the Pagid and Hawk pads both have a chamfers on them? Based on the differing noises, I'm guessing the pad chamfer profile on each of those pads is different. A pad chamfer determines how the edge of the pad interacts with the face and slots/drill holes on rotors on discs, and are designed to prevent vibrations and noise. Since both the pad and disc are curved, without a chamfer, only the pointy leading edge of the brake pad material would first make contact with each slot or drill hole as each disc slot passes across the pad face. With a chamfer, a wider section of the pad's leading edge makes contact with slots, which can dampen the noise of that impact.




3. Pad transfer layer on the disc face- Are the pads bedded-in well on the disc face? When you get brakes pad hot enough, they stick to the disc face and lay down a pad transfer layer. The pads then run on a distributed layer of pad material, rather than the bare iron disc face. The pad transfer layer is a great noise dampener and has a big impact on the amount of noise your brakes make, particularly squealing noises. Just be careful when swapping between two different pad materials and trying to bed them in. Mixing two pad materials on the same disc face can be a recipe for vibration and judder. When the two pad compounds mix on the disc face, they can turn into a clumpy, gooey mess. This is especially true when two different brands of pads are run on the same discs, which are many times made from completely different materials and processes. The videos below look at the bedding and pad swapping processes in great detail.




4. Pad backing plate condition- This one is much less common, but can still occur. How the brake pads slide in the brake caliper differs by caliper type. If the pads are sliding on any type of pin, the condition of the edges of the brake pad can impact how smoothly it slides. For example, if part of the pad's top or side edge has had the paint scraped off, but part is still covered in smooth paint, the pad may not engage and disengage the disc face smoothly when it is squeezed by the caliper.

JRitt@essex

My recommendation for action would depend on how often your friend plans to track his car. If he plans to run it on the street, I would suggest:

• Run the car on the street for a couple weeks with the Pagid Yellow race pads in the calipers. When run cold, race pads scrape the pad material off the disc face. If you watch the second video I posted above, you'll see me go through this process on my car. Cold race pads can peel the pad transfer layer off the discs, creating a blank iron canvas on which one can lay down a different pad material.
• Once the Pagid pad transfer layer has been removed, then install the Hawk Performance Ceramic Pads.
• Do a full bed-in cycle per my first video above, to establish a pad transfer layer with the Hawk pad material
• If that doesn't work, he may want to try a different street pad with a different pad chamfer profile

If he then wants to take the car to the track, he needs to install the Pagid Yellows and again run them cold on the street for a while to scrape off the Hawk pad transfer layer. Once the discs are clean, then lay down a Pagid pad transfer layer via the bed-in process.

Depending on how often he wants to track the car, he may want to just get a set of cheap street discs and bed the Hawk pads onto those discs. He can reserve the AP racing discs to run with the Pagid Yellows on track.

Another option is to go with Ferodo pads, which have been proven to work extremely well with our AP Racing iron. The Ferodo DS2500 as a street/autoX pad is often run on the same discs as Ferodo's pure racing compounds like the DS1.11 and DS3.12. Since these Ferodo compounds are all made from the same core materials, you can switch between street (DS2500) and track compounds without having to worry about cleaning the discs and laying down a new pad transfer layer. You just pop the new pads in, get them seated with a few moderate stops, and you're good to go. The full range of Ferodo pads for the 997.2 Turbo can be found here: https://www.essexparts.com/my-vehicl...bo/Iron%20disc

Hopefully all the above helps! Let me know if you need further guidance and thanks for reaching out.

Edcantera

Thank you very much for the detailed response! We are going to go down the list and report back on how things progress. He recently purchased the car so we have no way of knowing how much track time it has but given that it came with a track based brake setup I’d guess it saw some decent amount of time.