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What's up with this transfer from onto my rotors?

So I'm at a track day today, and during the second session I start to notice a thumping when I'm braking.

It gets worse as the day goes on. So I pulled a wheel off, and this is what my rotor looks like. Any ideas why this happened or how to fix it?

14+-+1
 
What pads?

I didn't experience this with carbotechs, but I have experienced it on my corolla with Hawk HP+'s. I just kept braking hard and it eventually went away.
 
These are Pagid RS29 pads, which have had maybe 9 track sessions on them and were about 40% pad remaining.

I just had the rotors resurfaced, then put these pads on.

I tried my best to bed the pads in properly, making 5-6 hard stops from 90-ish down to 40-ish, then doing some "recovery stops" with lighter braking, then cruising at 60 for a while to lets things cool off.
 
I had a little of that my first time using my Pagid pads on new rotors but nothing like that. I have DBA 4000 T3 rotors with slots. I used the Pagid procedures for bedding in the pads. I drove mine on the street afterwards and that cleaned them off and haven't seen it again. I'm on my second set of RS-29's and I'm about to order another set for my Stoptech calipers and rotors.
 
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I had the same thing happened with my Pagid pads. At first I thought it was the rotors so I replaced the rotors and after a few sessions it came right back. I talked to a few other guys who have had the same issue. I never experienced any brake fade but the vibration you feel through the pedal just doesn't feel right. I am up for suggestions on a different set of pads…I know a lot of guys use carbotech pads.
 
My vibration is now to the level of being alarming. Kinda ruined my last two sessions today...
 
Stock rotors and pads well bedded and several track sessions. After last track day everything was good on the track. Drove home about an hour with minimal braking and noted pedal pulse at end of the trip. Inspection through the wheel spokes looked like picture above. A couple of normal commutes cleaned them up and feel fine ever since.
 
I had deposits with carbotech pads. Driving the car for a hundred miles or so cleaned up the rotors. Also found that a few semi-hard stops with cold pads cleaned up the deposits a little more quickly.

A few things that help:
1. I only buy pre-bedded pads now.
2. Changed my braking style from waiting until the very last second and nailing the brakes HARD to getting on and off the brakes a little easier.
3. Bought some of the slotted T3 slotted rotors that KNS Brakes had on sale a while back. So far I find I can hit the new rotors pretty hard without pad deposit. I like these rotors, but they are slightly heavier than stock.
 

PeteInCT

#LS-378 - So many Porsche's, so little time....
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As with any high performance pads you need to bed them in properly. This means they need to get HOT. The endurance pads like the RS-29 are even more critical to bed in properly. This can also be partially caused by mating new pads with used rotors.

-Pete
 
The buildup of brake pad material is not normal. It is most likely caused by one and/or both of the following. Improper bed in procedure and/or the brake pads being over heated. Stop tech has a excellent article that best explains this condition. Also once this buildup has occurred it is likely to repeat itself even if the rotors are resurfaced as noted in the Stop Tech article. http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

V/r Chris
 
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HackBoss302 said:
The buildup of brake pad material is not normal. It is most likely caused by one and/or both of the following. Improper bed in procedure and/or the brake pads being over heated. Stop tech has a excellent article that best explains this condition. Also once this buildup has occurred it is likely to repeat itself even if the rotors are resurfaced as noted in the Stop Tech article. http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

V/r Chris

I have had this same problem with the RS-29 pads. But, Pete is right, they probably are not fully bedded. I had about six track days on my pads when they stopped transferring materials. Bottom line, you have to get the RS-29s a lot hotter than you might expect. Mine stopped transferring material after several sessions on track where the front brakes were smoking coming off the track. Essentially, when I first put the pads on I was not driving the car hard enough to properly bed the pads.....

The RS-29 pads will also clean the rotors back up. Just drive the car on the street normally and the vibrations will go away.

Steve
 

PeteInCT

#LS-378 - So many Porsche's, so little time....
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In the case of the Pagid pads it is most probably the former and not from overheating. RST-2 pafs handke up to 1500 degrees F. As for being 'normal', this true if they are bedded in well. Its very normal and expected if you don't. As far as not bring able to get rid of the deposits, you most certainly can get rid if deposits if the pads eventually are baked in well enough. And the deposits will eventually wear off.

[email protected]
 
I'd read that before... but in reading it again it's really hitting home for me. Thanks for the reminder, Chris.

I'll try these pads one more time, paying more careful attention to the bedding process. It's tricky because I really did try to bed them.

I didn't follow Pete's instructions to the letter http://www.trackdaysolutions.com/bedding_procedure.html... instead trying to follow these instructions I found from Pagid: http://www.pagidracing.com/fileadmin/pagidracing/content_data/downloads/pagid_bedding_in_procedure.pdf

Guess I got it wrong. Not *way* wrong... but wrong. Perhaps that's why it seems a lot of folks have trouble with their pads... they "do their best" to achieve a bedding procedure that's very, very difficult to do on public roads. And maybe bedding is one of those things where if you didn't get quite enough heat in the pad, you are going to have a bad time. Getting 85% of the way may not work at all.
 

PeteInCT

#LS-378 - So many Porsche's, so little time....
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I will need to update our website, we still have the 'old' PAGID official bedding-in procedure. I am doubtful there either is 'wrong' since the PAGID compunds have not changed, however my assumption is the new procedure is a better alternative. Here is the update:


From Pagid's website

PAGID race pad mounting and bedding in

MOUNTING NEW PADS ON USED DISCS (rotors)

We do not recommend using discs, which are pre-bedded, or have been used with friction material other than PAGID. When Pagid race pads are installed on top of a layer of incompatible pad material, bedding might take much longer or in worst case won t work at all. It can also result in sub-optimal brake performance. Used discs have a slight ridge on the outer and inner edge (radius). For a little while, until bedded, new pads would ride only on this ridge and not on the complete disc surface. That can cause a soft pedal. Therefore it is recommended to chamfer the outer and inner edges of new pads a little bit in order to have full pad contact from the beginning. That is very important in long endurance races with pad changes to provide a firm pedal right after the pit stop.
BRAKE DISCS (rotors)

PAGID racing brake pads can be used either on solid, grooved or cross-drilled discs. If possible, pads should be bedded on used but NOT worn out brake discs. (If bedding new pads on new discs, focus on disc bedding first.) For disc bedding please refer to the disc manufacturers own instructions. Usually, disc bedding is performed at lower temperatures than pad bedding.
Why bedding?

To transfer a layer of friction material onto the brake disc (rotor) faces to achieve maximum performance.
To stabilize compressible materials to avoid a spongy pedal.
To boil off volatile elements in the friction compound in order to have the initial green fading during bedding and not during the race.
To align the pad surface with the brake disc (rotor) surface to have full contact.

If pads do not get bedded properly and / or used too hard right out of the box will likely lead to pad glazing. Pad glazing is a condition where the resins in the pad crystallize on both, the pad friction surface and the brake disc (rotor) surface, resulting in poor stopping performance, brake judder and vibrations. Also rapidly escaping volatile elements and moisture from the resin would seek an immediate escape route out of the friction compound, creating small fissures that would lead shortly to cracking and chunking.
Recommended vehicle bedding in procedure
1. Breaking-In

(creating a perfect contact-pattern between rotor and brake pad surface)
10 stops with low pressure and low temperature from 150 km/h (90 MPH) to approximately 80 km/h (50 MPH). Distance between each brake stop approximately 600 – 800 meters ( 600 to 800 yards).

2. Heating-Up

(Warm up in order to initiate some core heat in the whole brake system)
A sequence of 5 stops with medium to high pressure from 180 km/h (112 MPH) to approximately 60 km/h (37 MPH) with maximum acceleration between the stops. After the last stop cool down for 3 minutes with the speed preferably not higher than 100 km/h (62 MPH).

3. Recovery stops

3 to 5 stops with low pressure from 150 km/h (90 MPH) to approximately 80 km/h (50 MPH). Distance between each brake stop approximately 600 – 800 meters ( 600 to 800 yards).
PLEASE NOTE

It is imperative that the bedding in procedures are NOT performed on public roads. PAGID racing materials are NOT for street use. Failure to follow bedding in procedure may result in a sub-optimal brake performance.


Avoiding Brake Judder

During bedding and shortly after, some judder is quite normal but should disappear after 5 to 10 laps. Changing back and forth between two incompatible friction materials (e.g. racing brake pads of different brands or street pads) can cause uneven build-up of pad material on the disc surface and can consequently lead to brake judder. Judder is the result of a thickness variation in pad buildup on the disc surface. Brake judder can be from a barely noticeable vibration to a violent judder. When you install Pagid race pads on top of a layer of an incompatible pad material, bedding might take much longer or in worst case won t work at all. It can also result in sub-optimal brake performance.
Another reason for uneven pad transfer is called imprinting . After coming to a complete stop with hot brakes (in the pits or after a spin), do not keep your foot on the brake pedal. The hot pads can leave a deposit behind that in turn again can cause judder and vibrations.
 
Okay, I'll try this next. Here are Pete's new instructions, translated into a form that I can do:

Brake with low pedal pressure from 90 MPH to 50 MPH, then drive 1/4 mile
Repeat above step 9 times

Brake with medium/high pressure from 112 MPH to 37 MPH
Repeat above step 3 times

Drive 62 MPH for 3 minutes

Brake with low pedal pressure 90 MPH to 50 MPH, then drive 1/4 mile
Repeat above step 3 times
 
Pete, it's not easy finding a place to go 112 MPH... is it possible step 2 could be modified a bit? Such as: "do 6 stops from 90 to 50"? Or it is essential to perform these very long stops?
 

ArizonaBOSS

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Stuff a couple microfiber towels into the brake duct inlets to block them off while bedding, that will help speed the process.

FWIW when I get new pads I just bed them at the track; I jump out at the back end of the new member group and punch in 2-3 laps of bedding procedures (including some 100+ MPH stops), then either return to the pits and let the car cool or pit, have the towels removed, then hit the track again for another 2-3 laps using the brakes minimally to get the proper cooling.
 

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