******* Brake Burnishing*******
09-20-2012, 07:27 PM
#21
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Yours are more severe in appearance from pic at top of sticky. I wonder if the white on yours will fall off revealing a permanent more narrow white band. Have you rechecked the appearance after some washes, rain, driving, etc?
09-20-2012, 08:38 PM
#22
lifeislikeaboxofchocolats
They still look the same..and have been washed many times..
Last edited by Nanook; 03-12-2013 at 09:17 PM.
09-20-2012, 09:10 PM
#23
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I'm going to give it another go. I want to get track burnishing accomplished anyhow. Will report back. I'm mostly looking for a more sudden reaction at the top of the pedal, elimination of wooden feel, and prevention of green fade.
10-04-2012, 10:29 PM
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Take Two
Second attempt had very different feel than first. Peddle felt good from the start, no fade to speak of, pouring smoke once hot, but still wanted to suck your eye ***** out. I decided to let her cool down and give it a look. I now have a nice frosting on the pads, which was mostly missing after the first attempt. I'm attending an HPDE/educational event this weekend, so I am glad to have prepared the breaks for some use. 
By the way, I now have the CUP tires on. They are sticky, but seems to wonder/pull under heavy breaking. The PS2's seem to track much better under this condition. Under acceleration the CUP's definitely put the power down better. Anyone else noticed anything similar?
By the way, I now have the CUP tires on. They are sticky, but seems to wonder/pull under heavy breaking. The PS2's seem to track much better under this condition. Under acceleration the CUP's definitely put the power down better. Anyone else noticed anything similar?
10-07-2012, 06:07 AM
#25
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02-13-2013, 11:56 AM
#27
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Short answer is yes. You should make sure of the procedures for your breaks first. There is a vid on here of a guy doing burnishing on mustang. He pretty much did same procedure as our manual specifies.
03-29-2013, 05:48 PM
#29
Le Mans Master
I think i need to burnish my brakes, b/c as soon as the get hot it feel like i have to press way more harder the brake for stop. How could i burnish it on the street though???
03-29-2013, 05:54 PM
#30
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I'm not sure what it's like, road wise, where you are. The easiest thing for most of us to do is find an untraveled back road, and hit it during the wee hours of the morning. Like say 0200-0300 or so. The likelihood of patrols at that hour is smaller.
jas
03-29-2013, 06:13 PM
#31
Le Mans Master
Im glad to hear that, because i was REALLY disapointed in the carbon brake being weaker than my Z06 brake! Even after when they are still hot low speed bite seem to be lousy. I definitively need to burnish the brake, but the big question HOW???
03-29-2013, 08:31 PM
#32
Race Director
Timmy, bring along a friend to ride with you, help watch for traffic, etc.
The drill is in this thread, and in the OM: 50 pulls/stops from 0 to 60 mph to almost 0, completed in 10-12 minutes.
You can use 2nd gear for all this... then drive 15 minutes at highway speed without using the brakes at all, for proper
cool down.
When done, you should see the white line/edge on the pads where the same contact the rotor...
a large empty shopping mall parking lot will also do, when no one is around... G-L !
The drill is in this thread, and in the OM: 50 pulls/stops from 0 to 60 mph to almost 0, completed in 10-12 minutes.
You can use 2nd gear for all this... then drive 15 minutes at highway speed without using the brakes at all, for proper
cool down.
When done, you should see the white line/edge on the pads where the same contact the rotor...
a large empty shopping mall parking lot will also do, when no one is around... G-L !
05-27-2013, 07:34 PM
#33
Racer
Why do I have to burnish the brake pads in my new ZR1 or Z07-equipped Z06?
Pad Burnishing
The pad material that's riveted to the pad backing is made by pouring a slurry of muck into a mold and letting it set. That slurry of muck includes a bonding agent, or glue of sorts. That agent needs to be there, but it will cause a problem if the pads get overly hot.
When a non-burnished pad gets hot (I don't know the exact temp), the bonding agent will begin to out-gas and boil off. What happens with that gas is that it forms a barrier between the pad and the rotor. An air cushion of sorts. And an air pocket pressing against a spinning rotor is not as effective at stopping the car as a pad pressing against it.
The driver experiencing this will note that the pedal will get somewhat soft and resist slightly when they try to slow the car down. Simply pressing the pedal harder will force the air pocket to evacuate, and the pad will then come into contact with the rotor.
This unsettling feeling is called green fade. It feels like the pad is fading, but it isn't. The car will stop, but it takes a harder pedal press to make that happen.
Thus the burnishing procedure. The stops in question need to be done sans ABS, ie threshold braking the car, so that a constant pressure is kept on the pad during the stop. This is to help build up the heat in the pad. The goal here is to bake off the top layer of bonding agent from the pad so that an air pocket forming becomes impossible or highly unlikely.
GM has determined that, on average, it takes 50 60-0 stops in 10 minutes' time to get the pads hot enough for that. Basically what you're looking for is the pad to start fading bad during the procedure. That generally happens around stop 40 or so, when braking distances feel like they're increasing dramatically. Once this point has hit, the gasses are beginning to boil off. A few more stops after that point and the brakes will feel like they're grabbing before you even touch the pedal. At that point: you're done. Drive the car for a while at legal speeds to cool the pads.
Why not bake ALL of the bonding agent out? Well, if you do that, the entire pad will fall apart. That's not a good idea, right? Instead, the pad will continue to slowly boil off the rest of the bonding agent over time as you wear the pad down. You'll never notice it happening though.
How do I know I've done it right?
As described in the owners manual, once you've correctly burnished the pads, you'll see a white outline around the edge of the pad, right where it meets the rotor. It'll look something like this:
What's the track burnishing procedure for?
The street burnishing procedure is to prevent green fade, as described above. Your owners manual also describes a track burnishing procedure, which has you perform a series of 7 or 8 laps at your local road course, and then park the car after a cool-down lap. The first few laps should be done at increasing speed, and the last few should be done at slower and slower speeds.
Why do this? To further season the pads for high-temp use. The street burnishing preps the pads, and is enough for cars that are only driven on the street. But those that see continued high temps (ie, high speeds) at the track will need to perform this procedure after they perform the street one.
But I never drive my car really fast. Do I need to do the burnishing?
There's a lot of miss-information out there that the street burnishing procedure only needs to be performed if you're going to race or track your car. That statement needs to clarified carefully, to: if ALL you do is drive your car on the street and highways at legal speeds and NEVER intend to carve canyons, drive quickly up or down a mountain road, or perform high-speed runs (legal or otherwise), then you don't need to perform the burnishing. However, if there's even a remote possibility that you will do any of those things, it'd behoove you to at least perform the street burnishing.
Failing to do that with pads that get heated up will likely result in green fade, and a very uncomfortable driver.
jas
Pad Burnishing
The pad material that's riveted to the pad backing is made by pouring a slurry of muck into a mold and letting it set. That slurry of muck includes a bonding agent, or glue of sorts. That agent needs to be there, but it will cause a problem if the pads get overly hot.
When a non-burnished pad gets hot (I don't know the exact temp), the bonding agent will begin to out-gas and boil off. What happens with that gas is that it forms a barrier between the pad and the rotor. An air cushion of sorts. And an air pocket pressing against a spinning rotor is not as effective at stopping the car as a pad pressing against it.
The driver experiencing this will note that the pedal will get somewhat soft and resist slightly when they try to slow the car down. Simply pressing the pedal harder will force the air pocket to evacuate, and the pad will then come into contact with the rotor.
This unsettling feeling is called green fade. It feels like the pad is fading, but it isn't. The car will stop, but it takes a harder pedal press to make that happen.
Thus the burnishing procedure. The stops in question need to be done sans ABS, ie threshold braking the car, so that a constant pressure is kept on the pad during the stop. This is to help build up the heat in the pad. The goal here is to bake off the top layer of bonding agent from the pad so that an air pocket forming becomes impossible or highly unlikely.
GM has determined that, on average, it takes 50 60-0 stops in 10 minutes' time to get the pads hot enough for that. Basically what you're looking for is the pad to start fading bad during the procedure. That generally happens around stop 40 or so, when braking distances feel like they're increasing dramatically. Once this point has hit, the gasses are beginning to boil off. A few more stops after that point and the brakes will feel like they're grabbing before you even touch the pedal. At that point: you're done. Drive the car for a while at legal speeds to cool the pads.
Why not bake ALL of the bonding agent out? Well, if you do that, the entire pad will fall apart. That's not a good idea, right? Instead, the pad will continue to slowly boil off the rest of the bonding agent over time as you wear the pad down. You'll never notice it happening though.
How do I know I've done it right?
As described in the owners manual, once you've correctly burnished the pads, you'll see a white outline around the edge of the pad, right where it meets the rotor. It'll look something like this:
What's the track burnishing procedure for?
The street burnishing procedure is to prevent green fade, as described above. Your owners manual also describes a track burnishing procedure, which has you perform a series of 7 or 8 laps at your local road course, and then park the car after a cool-down lap. The first few laps should be done at increasing speed, and the last few should be done at slower and slower speeds.
Why do this? To further season the pads for high-temp use. The street burnishing preps the pads, and is enough for cars that are only driven on the street. But those that see continued high temps (ie, high speeds) at the track will need to perform this procedure after they perform the street one.
But I never drive my car really fast. Do I need to do the burnishing?
There's a lot of miss-information out there that the street burnishing procedure only needs to be performed if you're going to race or track your car. That statement needs to clarified carefully, to: if ALL you do is drive your car on the street and highways at legal speeds and NEVER intend to carve canyons, drive quickly up or down a mountain road, or perform high-speed runs (legal or otherwise), then you don't need to perform the burnishing. However, if there's even a remote possibility that you will do any of those things, it'd behoove you to at least perform the street burnishing.
Failing to do that with pads that get heated up will likely result in green fade, and a very uncomfortable driver.
jas
Also, did you indicate the procedure needs to be done without ABS ? If so, how do we deactivate ABS.
Sorry for the "rookie" questions, but I do want to make sure I maintain the vette correctly.
I so much appreciate your technical explanation.
Mark.
05-28-2013, 02:36 AM
#34
Carbon-ceramic matrix (CCM) brakes can be rebedded at any time. The main difference between these and the more common iron rotors is that the CCM rotors do not really wear, so they do not contribute to brake torque like iron does. This means the pad needs to do all the work -- almost 100% abrasive friction and almost 0% adherent friction. With iron rotors, some of that brake dust on those nice wheels is from the rotor itself, one of the reasons CCM-equipped vehicles keep the wheels a lot cleaner.
During the burnishing and bedding procedure, a transfer layer of pad material is deposited onto the CCM rotor surface. When this "freezes" during cool-down (arguably the most important part of the process), it creates a friction layer that the pad can now grab onto. It has nothing to do with pad off-gassing, an issue that went away many years ago, just like the old riveted pads did.
This process is also important for iron rotors, but for them it is easier to achieve and a little less critical in the approach. Neither should be done in a way that would cause the ABS to activate, or it is simply being overdone. The key is a nice slow temperature ramp-up, continued energy input to lay down the transfer layer, then a gradual cool-down to freeze it evenly. Uneven transfer layers are the #1 cause of brake pedal pulsation, often referred to mistakenly as "warped rotors". Follow GM's (actually Brembo's) procedure and things should work out well.
Transfer layers will wear off over time, more so with light braking use than with more aggressive braking. If you find that a few months down the road your braking performance is less than it used to be, run through the bedding procedure again and they should come right back. You won't likely need the full procedure as burnishing (mating the new surfaces to remove high spots) needs to be done only once. Transfer layer bedding usually takes less time on used parts that are already burnished.
Chris
During the burnishing and bedding procedure, a transfer layer of pad material is deposited onto the CCM rotor surface. When this "freezes" during cool-down (arguably the most important part of the process), it creates a friction layer that the pad can now grab onto. It has nothing to do with pad off-gassing, an issue that went away many years ago, just like the old riveted pads did.
This process is also important for iron rotors, but for them it is easier to achieve and a little less critical in the approach. Neither should be done in a way that would cause the ABS to activate, or it is simply being overdone. The key is a nice slow temperature ramp-up, continued energy input to lay down the transfer layer, then a gradual cool-down to freeze it evenly. Uneven transfer layers are the #1 cause of brake pedal pulsation, often referred to mistakenly as "warped rotors". Follow GM's (actually Brembo's) procedure and things should work out well.
Transfer layers will wear off over time, more so with light braking use than with more aggressive braking. If you find that a few months down the road your braking performance is less than it used to be, run through the bedding procedure again and they should come right back. You won't likely need the full procedure as burnishing (mating the new surfaces to remove high spots) needs to be done only once. Transfer layer bedding usually takes less time on used parts that are already burnished.
Chris
05-28-2013, 03:41 AM
#35
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During the burnishing and bedding procedure, a transfer layer of pad material is deposited onto the CCM rotor surface. When this "freezes" during cool-down (arguably the most important part of the process), it creates a friction layer that the pad can now grab onto. It has nothing to do with pad off-gassing, an issue that went away many years ago, just like the old riveted pads did.
Sorry Chris, but your information isn't correct. These pads do off-gas, and that's what creates the green fade as I'd written. Further, they're actually riveted.
Simply put: if you transfer any layer of anything from the pads to the rotors, you've destroyed the rotors. There is no bedding done here. Purely pad burnishing.
jas
05-28-2013, 07:19 AM
#36
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Hi Mark -
Absolutely. You can do it at any point. In fact, if and when you change your brake pads, you'll need to do it again.
You needn't deactivate the ABS. If you deactivated the ABS, you'd run the risk of flat-spotting and destroying your expensive street tires. All you need to do is brake with enough force on the pedal to stop the car, but not engage ABS. It may take a little practice, and the amount of pressure you need on the pedal will change throughout the procedure. Does that make sense?
jas
Also, did you indicate the procedure needs to be done without ABS ? If so, how do we deactivate ABS.
jas
05-28-2013, 11:22 AM
#37
Sorry Chris, but your information isn't correct. These pads do off-gas, and that's what creates the green fade as I'd written. Further, they're actually riveted.
Simply put: if you transfer any layer of anything from the pads to the rotors, you've destroyed the rotors. There is no bedding done here. Purely pad burnishing.
jas
Simply put: if you transfer any layer of anything from the pads to the rotors, you've destroyed the rotors. There is no bedding done here. Purely pad burnishing.
jas
- They are much higher temperature rated than pads for iron rotors. In fact, they are typically slightly modified version of endurance racing pads (I have used Pagid RS29 before with pretty darn good results on the street). This is necessary because pads run much hotter on CCM rotors than they do iron as they have much less mass to absorb thermal energy. Both the pads and calipers experience much higher running temperatures than with iron brakes, which is why cooling is even more important. The binders in high temperature pads are already cooked out and converted to carbon during the final manufacturing process, something that is not done for lower temperature pads.
- Low temperature pads often contain rubber and other compounds to help with low temperature friction and to damp vibrations that cause noise. These are the materials that will off gas during green fade. Pads for CCM rotors cannot contain many of these elements as they will fade way too early at the higher temperatures. Besides, they'd be cooked off during post-cure anyway. As a result, off-gassing is negligible.
I will say that it is too bad that GM is not supplying brake rotors that are already pre-bedded, which could be done by Brembo on their brake dynos. Bedding CCM rotors is more difficult than iron it takes longer to lay down a transfer layer with high-temp pads, and there are far better ways to do it than taking a $100k+ car out on city streets!!
Also, I've never seen a riveted pad running on ceramic brakes (but I haven't seen every single one of them yet!). Once a rivet head touches the rotor surface, you are looking at a new rotor at around $2000 or so. I do know the pads manufactured by Ferodo and Pagid (who supply nearly all the pads for OE CCM applications -- Ferodo for AP Racing and Pagid for Brembo) do NOT have rivets, nor are they even necessary any more. Using NRS (Nucap) technology, rivets went the way of the dodo bird quite some time ago, with the exception of the $14.99 sets at the discount parts stores. Don't we wish pads for CCM rotors only cost that much!!
Chris
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05-28-2013, 11:44 AM
#38
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There are a couple of folks here in the ZR1 section who experienced said green fade when they first got their cars. The mushy, spongy pedal, and uneasy feeling of braking competence. And it's directly due to them not burnishing the pads.
I will say that it is too bad that GM is not supplying brake rotors that are already pre-bedded
which could be done by Brembo on their brake dynos.
Also, I've never seen a riveted pad running on ceramic brakes (but I haven't seen every single one of them yet!).
jas
05-28-2013, 11:44 AM
#39
Racer
Hi Mark -
Absolutely. You can do it at any point. In fact, if and when you change your brake pads, you'll need to do it again.
You needn't deactivate the ABS. If you deactivated the ABS, you'd run the risk of flat-spotting and destroying your expensive street tires. All you need to do is brake with enough force on the pedal to stop the car, but not engage ABS. It may take a little practice, and the amount of pressure you need on the pedal will change throughout the procedure. Does that make sense?
jas
Absolutely. You can do it at any point. In fact, if and when you change your brake pads, you'll need to do it again.
You needn't deactivate the ABS. If you deactivated the ABS, you'd run the risk of flat-spotting and destroying your expensive street tires. All you need to do is brake with enough force on the pedal to stop the car, but not engage ABS. It may take a little practice, and the amount of pressure you need on the pedal will change throughout the procedure. Does that make sense?
jas
Mark.
05-28-2013, 01:08 PM
#40
Burning Brakes
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If I might jump in the middle of this a bit. I don't believe our pads green fade from off gassing, as the drilled rotors would vent that handily if it occurred. According to the Brembo rep that I spoke with, the holes are in the rotors for marketing purposes because customers want to see them, not because they do anything functional. He said the green fade occurs from the pad adhesive "cooking" out of the pad when it gets hot. If they took that out at the factory, the pads would not hold together properly. As the pad wears, the burnishing needs to be reaccomplished occasionally as you wear down to another layer where the adhesive remains.