Aug 22, 2007 10:33:54 AM
- Yorkie997GT3
- Newbie
-
- Loc: Yorkshire
- Posts: 1, Gallery
- Registered on: Oct 24, 2006
Crown
Board: Porsche - 911 - 997
Language: English
Region: Worldwide
Close
CloseForum - Thread
Aug 22, 2007 11:11:20 AM
- MarekN
- Pilot
-
- Loc: Czech Republic
- Posts: 409, Gallery
- Registered on: Jun 7, 2006
- Reply to: Yorkie997GT3
Re: 997 GT3 Brake Squeal
Hello to you! Expect to get the usual "post some pictures" requests, so bring them on. How long have you had the car?
This has been covered many times and seems to be common for steel and PCCB. It appears that you have to re-bed the brake pads, i.e. scrub their material onto the rotors.
The usual comment for squealing brakes is that you don't drive your car hard enough. General recommendations go something like this:
Go out and accelerate to 60 mph, apply brakes moderately (not lightly, but also not too abruptly) and slow down to 15 mph, do this ten times over. Than accelerate to 80 mph and brake to a full stop. Take off again and drive around for a few minutes to cool the brakes off.
Another general rule is to remember not to stand on the brake pedal when stationary after heavy use, as this may result in warped rotors and/or baked pad material in that part of rotor and subsequent middle pedal vibration.
This has been covered many times and seems to be common for steel and PCCB. It appears that you have to re-bed the brake pads, i.e. scrub their material onto the rotors.
The usual comment for squealing brakes is that you don't drive your car hard enough. General recommendations go something like this:
Go out and accelerate to 60 mph, apply brakes moderately (not lightly, but also not too abruptly) and slow down to 15 mph, do this ten times over. Than accelerate to 80 mph and brake to a full stop. Take off again and drive around for a few minutes to cool the brakes off.
Another general rule is to remember not to stand on the brake pedal when stationary after heavy use, as this may result in warped rotors and/or baked pad material in that part of rotor and subsequent middle pedal vibration.
Aug 22, 2007 11:30:15 AM
- amir sarmad
- Veteran
-
- Loc: dubai, UAE
- Posts: 909, Gallery
- Registered on: Mar 30, 2005
- Reply to: Yorkie997GT3
Re: 997 GT3 Brake Squeal
When i first got my 987, everything was perfect in regards to brake squeals. But then after 20k km i started hearing them and they started getting embarrassing. i used to think that cheaper cars only squealed. I went to the dealer and told them my problem. the dealer said that this was a problem with all Porsche brakes. WTF!!this doesn't make sense, so i went to a third party garage and they finally agreed to apply some brake squeal lube. They did however mention that the squeal would come back. I was real frustrated for a long time, I never had this problem on my previous m3 or m6 (i did have tons of other problems though). After asking around i found out that this is normal and not a problem. Brake bads create friction to stop, and this sometimes causes vibrations which in return causes squealing. Anyhow, after everything i learned to live with it forgot about it till it started getting worse. Then i started to ask around again. Some poeple said that i had an improper brake in, or my braking style was wrong. other people said that this is normal and that i just have to brake hard at high speeds to get rid of the squeal. i just gave up and decided to leave it again. Today i installed a 3rd high performance break pad ( EBC YEllow STUFF)and belive me, consider your self lucky, cuz my brakes SCREAM!! . therefore rest assure that all high performance brake pads do the following
a) squeal
b) create dust
never the less i have enclosed a a diagram from EBC brakes on why squealing occurs. Incase you were wondering, Don't buy the yellow stuff if you cant stand the squealing!
A - SHIM NEEDED - 60% of brake noise problems are solved by the addition of a rubber/steel/rubber shim on the reverse of the pad known as a noise reduction shim. Since 2006 all EBC Greenstuff, Redstuff and Yellowstuff pads have been manufactured with shims.
However, if your pad set does not have such shims ask for a set of these free of charge from EBC support, fit them and reinstall pads.
B - CHAMFER - Chamfering or bevelling the edges of the friction material is now done by EBC in all production. Chamfers can eliminate noise in approximately 10% of cases. Sometimes a larger than standard chamfer may be necessary due to driving styles or conditions but seek advice from EBC technical support before attempting this modification at home.
C - DRIVING STYLE - Regular city driving with frequent and light brake applications can cause pads to glaze. If noise gradually develops in such driving conditions use the brakes 2-3 times from higher speeds to load brakes more positively on a quiet road when it is safe to do so. This has the effect of deglazing the pad surface.
D - BED-IN - Most noise problems come in the first few miles of use and pads must be given a chance to bed-in. Bed-in times are extended if rotor is not turned or surface is off-flat. Even the slightest hollow in the surface of the rotor can extend bed-in time up to 500 miles. Ask customers to run vehicle for at least 500 miles.
E - SPORT ROTORS - have been shown to run quieter in many cases than plain rotors especially the EBC sport rotor which has scraper slots and helps to deglaze the pad surface and break down harmonics.
F - DRAG - In approximately 5% of cases when new pads are installed the hydraulic pistons in the caliper are pushed back and then seize when driving the vehicle after pad fitment causing drag. This can cause noise but often also shows uneven wear on the left and right hand sides of the vehicle, or on one single pad.
G - ROTOR QUALITY - With many cheap import brake rotors now on the market a quality pad with good brake effect can actually damage the rotor by picking up small disc material particles which then act like a small machining tool on the remaining rotor surface. This is detected by looking at the pad surface and seeing silver particles within the pad which have been picked up from the brake disc. Solution is to either use EBC pads with Brake-InTM coating or to scuff the brake rotor with a scratch pad and remove the silver particles from within the pad surface then reinstall and try again.
3. Brake vibration (rotor shimmying or brake pulsation)
Many good technical articles have been written about this problem which is without doubt the number one regular brake problem encountered. We will give you a short easy to understand recap.
When new brake rotors are installed it is absolutely essential that they run true. All EBC rotors are manufactured and inspected to have less than 0.002 inches (.05mm) of run out. If after your new rotors are installed they have more than this amount of run out, then there is a run out problem on your car. This can be quite easy to resolve and is usually due to one of two things. First the mounting faces where the disc locates on your vehicle must be ABSOLUTELY CLEAN and free from rust or scale which develops during the lifetime of the old rotor. Even the tiniest amount of dirt or scale can throw these run out figures to five times the factory limit. After installing the rotors and tightening them using correct procedures by tightening wheel nuts diagonally with a torque wrench (not an airgun) it is vital to take a few minutes to check rotor run out with a dial gauge and if one of these is not available by holding a screw driver firmly against a part of the caliper body and rotating the disc / rotor to listen or look for distortion. If you do not correct distortion above 0.004 inches (0.1mm) at this point you will DEFINITELY experience brake judder within a few thousand miles. The actual cause of brake judder is not this run out figure (it will be almost impossible for you to detect small run out whilst driving) but over a period of time a "thin spot" would develop on an area of the rotor caused by intermittent pad contact which is known technically as DTV (disc thickness variation). As you apply pedal pressure these thin spots will cause pulsation. If the vibration or shimmying is noticed on the steering wheel it is usually a front rotor problem. The problem is usually only ONE ROTOR not necessarily the pair. If the pulsation is noticed through the bodywork of the car, such as the seat or brake pedal, it is usually a rear rotor that is at fault.
The solution for this vibration is one of two things. 1. either replace the rotors again with new units or 2. take them to your local autoparts store and ask for them to be turned or skimmed. The smallest cut of a few thousandths is all that is needed to correct this problem. When remounting the turned or new rotors, make sure run out is carefully checked as above.
The point at which this thin spot or DTV will occur depends on how regularly or irregularly the brakes are applied. If for example you drive 50 miles to work every day and hardly touch the brakes, it could appear as quickly as 500 miles. The reason for this is that regular use of the brakes tends to wear the whole surface of the brake disc at the same time whereas driving the vehicle "off the brake" causes an intermittent contact between the pad and the high spot on the rotor wearing this high spot down and causing DTV.
The second cause of brake vibration is black spotting of the rotor which is caused by the rotor over heating and a hard spot occurring intermittently around the rotor surface. This in technical terms is the formation of cementite which is a very hard by product of cast iron (rotor material) caused by over heat and sudden cooling. If you witness black spotting the only solution is to replace the rotor or have it turned. Black spotting occurs when the rotor has either worn too thin (having been turned more than once), or by brake pads that are ineffective in balancing rotor and pad temperatures. The problem for the consumer today is that all brake pads looks the same and people rely on the expertise of the guy across the counter who sells them their brakes. The design of brake pad materials is a very exact science and the difference between a company who knows what they're doing and one who doesn't is a few percentage points. Brake pads need to have good "thermal conductivity" to take the heat away from the rotor, optimum "compressibility" to allow the brake system to absorb or dampen minor vibrations and optimum "scrub factor". The latter is the ability of the pad to hone out minor surface imperfections on the rotor as they occur without wearing the rotor excessively. All three of these design criteria and a few hundred more are things that EBC Brakes specialises in. We could ramble on for hours here about how clever we are but the proof of the pudding we say is in the eating. We are confident you will have a great experience with EBC Brakes if you follow our guidelines and should you not find our products to meet your desires, we are an easy company to contact and very service oriented.
a) squeal
b) create dust
never the less i have enclosed a a diagram from EBC brakes on why squealing occurs. Incase you were wondering, Don't buy the yellow stuff if you cant stand the squealing!
A - SHIM NEEDED - 60% of brake noise problems are solved by the addition of a rubber/steel/rubber shim on the reverse of the pad known as a noise reduction shim. Since 2006 all EBC Greenstuff, Redstuff and Yellowstuff pads have been manufactured with shims.
However, if your pad set does not have such shims ask for a set of these free of charge from EBC support, fit them and reinstall pads.
B - CHAMFER - Chamfering or bevelling the edges of the friction material is now done by EBC in all production. Chamfers can eliminate noise in approximately 10% of cases. Sometimes a larger than standard chamfer may be necessary due to driving styles or conditions but seek advice from EBC technical support before attempting this modification at home.
C - DRIVING STYLE - Regular city driving with frequent and light brake applications can cause pads to glaze. If noise gradually develops in such driving conditions use the brakes 2-3 times from higher speeds to load brakes more positively on a quiet road when it is safe to do so. This has the effect of deglazing the pad surface.
D - BED-IN - Most noise problems come in the first few miles of use and pads must be given a chance to bed-in. Bed-in times are extended if rotor is not turned or surface is off-flat. Even the slightest hollow in the surface of the rotor can extend bed-in time up to 500 miles. Ask customers to run vehicle for at least 500 miles.
E - SPORT ROTORS - have been shown to run quieter in many cases than plain rotors especially the EBC sport rotor which has scraper slots and helps to deglaze the pad surface and break down harmonics.
F - DRAG - In approximately 5% of cases when new pads are installed the hydraulic pistons in the caliper are pushed back and then seize when driving the vehicle after pad fitment causing drag. This can cause noise but often also shows uneven wear on the left and right hand sides of the vehicle, or on one single pad.
G - ROTOR QUALITY - With many cheap import brake rotors now on the market a quality pad with good brake effect can actually damage the rotor by picking up small disc material particles which then act like a small machining tool on the remaining rotor surface. This is detected by looking at the pad surface and seeing silver particles within the pad which have been picked up from the brake disc. Solution is to either use EBC pads with Brake-InTM coating or to scuff the brake rotor with a scratch pad and remove the silver particles from within the pad surface then reinstall and try again.
3. Brake vibration (rotor shimmying or brake pulsation)
Many good technical articles have been written about this problem which is without doubt the number one regular brake problem encountered. We will give you a short easy to understand recap.
When new brake rotors are installed it is absolutely essential that they run true. All EBC rotors are manufactured and inspected to have less than 0.002 inches (.05mm) of run out. If after your new rotors are installed they have more than this amount of run out, then there is a run out problem on your car. This can be quite easy to resolve and is usually due to one of two things. First the mounting faces where the disc locates on your vehicle must be ABSOLUTELY CLEAN and free from rust or scale which develops during the lifetime of the old rotor. Even the tiniest amount of dirt or scale can throw these run out figures to five times the factory limit. After installing the rotors and tightening them using correct procedures by tightening wheel nuts diagonally with a torque wrench (not an airgun) it is vital to take a few minutes to check rotor run out with a dial gauge and if one of these is not available by holding a screw driver firmly against a part of the caliper body and rotating the disc / rotor to listen or look for distortion. If you do not correct distortion above 0.004 inches (0.1mm) at this point you will DEFINITELY experience brake judder within a few thousand miles. The actual cause of brake judder is not this run out figure (it will be almost impossible for you to detect small run out whilst driving) but over a period of time a "thin spot" would develop on an area of the rotor caused by intermittent pad contact which is known technically as DTV (disc thickness variation). As you apply pedal pressure these thin spots will cause pulsation. If the vibration or shimmying is noticed on the steering wheel it is usually a front rotor problem. The problem is usually only ONE ROTOR not necessarily the pair. If the pulsation is noticed through the bodywork of the car, such as the seat or brake pedal, it is usually a rear rotor that is at fault.
The solution for this vibration is one of two things. 1. either replace the rotors again with new units or 2. take them to your local autoparts store and ask for them to be turned or skimmed. The smallest cut of a few thousandths is all that is needed to correct this problem. When remounting the turned or new rotors, make sure run out is carefully checked as above.
The point at which this thin spot or DTV will occur depends on how regularly or irregularly the brakes are applied. If for example you drive 50 miles to work every day and hardly touch the brakes, it could appear as quickly as 500 miles. The reason for this is that regular use of the brakes tends to wear the whole surface of the brake disc at the same time whereas driving the vehicle "off the brake" causes an intermittent contact between the pad and the high spot on the rotor wearing this high spot down and causing DTV.
The second cause of brake vibration is black spotting of the rotor which is caused by the rotor over heating and a hard spot occurring intermittently around the rotor surface. This in technical terms is the formation of cementite which is a very hard by product of cast iron (rotor material) caused by over heat and sudden cooling. If you witness black spotting the only solution is to replace the rotor or have it turned. Black spotting occurs when the rotor has either worn too thin (having been turned more than once), or by brake pads that are ineffective in balancing rotor and pad temperatures. The problem for the consumer today is that all brake pads looks the same and people rely on the expertise of the guy across the counter who sells them their brakes. The design of brake pad materials is a very exact science and the difference between a company who knows what they're doing and one who doesn't is a few percentage points. Brake pads need to have good "thermal conductivity" to take the heat away from the rotor, optimum "compressibility" to allow the brake system to absorb or dampen minor vibrations and optimum "scrub factor". The latter is the ability of the pad to hone out minor surface imperfections on the rotor as they occur without wearing the rotor excessively. All three of these design criteria and a few hundred more are things that EBC Brakes specialises in. We could ramble on for hours here about how clever we are but the proof of the pudding we say is in the eating. We are confident you will have a great experience with EBC Brakes if you follow our guidelines and should you not find our products to meet your desires, we are an easy company to contact and very service oriented.
Aug 22, 2007 12:27:24 PM
- Boxster Coupe GTS
- Rennteam Master
-
- Loc: UK , United Kingdom
- Posts: 5884, Gallery
- Registered on: Feb 23, 2005
- Reply to: Yorkie997GT3
Pad and Rotor Bed-In Theory...
Pad and Rotor Bed-In Theory, Definitions and Procedures
"Removing the Mystery from Brake Pad Bed-In"
Pad+Rotor_Bed-In_Theory_LINK
In order for any brake system to work optimally, the rotors and pads must be properly bedded-in, period. This process can also be called break-in, conditioning, or burnishing, but whatever terminology you choose, getting the brakes properly bedded-in and keeping them that way is critical to the peak performance of the entire brake system.
However, understanding why the rotors and pads need to be bedded-in is just as important as the actual process. If one understands what is happening during the bed-in process, they can tailor the process to specific pads, rotors, and/or driving conditions. For this reason, we present this generic bed-in overview pertaining to all brake systems, but follow with links to application-specific bed-in procedures to fit most every set of circumstances.
- What is brake pad "bed-in" anyway?
Simply stated, bed-in is the process of depositing an even layer of brake pad material, or transfer layer, on the rubbing surface of the rotor disc. That's it. End of discussion. Ok, not really, but although bed-in is quite basic in definition, achieving this condition in practice can be quite a challenge, and the ramifications of improper or incomplete bed-in can be quite a-a-n-n-o-o-y-y-i-i-n-n-g-g.
- Abrasive friction and adherent friction
There are two basic types of brake pad friction mechanisms: abrasive friction and adherent friction . In general, all pads display a bit of each, with abrasive mechanisms dominating the lower temperature ranges while adherent mechanisms come more into play as pad temperature increases. Both mechanisms allow for friction or the conversion of Kinetic energy to Thermal energy, which is the function of a brake system, by the breaking of molecular bonds in vastly different ways.
The abrasive mechanism generates friction or energy conversion by the mechanical rubbing of the brake pad material directly on the rotor disc. In a crystalline sense, the weaker of the bonds in the two different materials is broken. This obviously results in mechanical wear of both the pad and the rotor. Consequently, both pads and rotors are replaced when they are physically worn to their limit and are too thin to endure further service.
The adherent mechanism is altogether different. In an adherent system, a thin layer of brake pad material actually transfers and sticks (adheres) on to the rotor face. The layer of pad material, once evenly established on the rotor, is what actually rubs on the brake pad. The bonds that are broken, for the conversion of Kinetic to Thermal energy, are formed instantaneously before being broken again. It is this brake pad-on-transferred brake pad material interaction on a molecular level that yields the conversion process.
With the adherent mechanism there is much reduced rotor wear as compared to abrasive mechanism, but it's not a free lunch - pads now become the primary wear element in the braking system. And even though rotors are not mechanically worn down with adherent systems, they still will need to be replaced on a regular basis due to cracking reaching a point of failure if they are exposed to intense, repetitive thermal cycling. This is why race teams throw out rotors that are actually as thick or thicker than when they were brand new. It's due to the an adherent brake pad transfer layer!
- The all-important transfer layer
As stated above, the objective of the bed-in process is to deposit an even layer of brake pad material, or transfer layer , on the rubbing surface of the rotor disc. Note the emphasis on the word even, as uneven pad deposits on the rotor face are the number one, and almost exclusive cause of brake judder or vibration.
Let's say that again, just so there is no misunderstanding. Uneven pad deposits on the rotor face are the number one, and almost exclusive cause of brake judder or vibration.
It only takes a small amount of thickness variation, or TV, in the transfer layer (we're only talking a few ten thousandths of an inch here) to initiate brake vibration. While the impact of an uneven transfer layer is almost imperceptible at first, as the pad starts riding the high and low spots, more and more TV will be naturally generated until the vibration is much more evident. With prolonged exposure, the high spots can become hot spots and can actually change the metallurgy of the rotor in those areas, creating "hard" spots in the rotor face that are virtually impossible to remove.
- Bedding fundamentals
In general, bed-in consists of heating a brake system to its adherent temperature to allow the formation of a transfer layer. The brake system is then allowed to cool without coming to rest, resulting in an even transfer layer deposition around the rotor circumference. This procedure is typically repeated two or three times in order to ensure that the entire rotor face is evenly covered with brake pad material. Sounds easy, right? Well, it can be if you have the proper information.
Because the adherent temperature range for brake pads varies widely (typically 100*F-600*F for street pads and 600*F-1400*F for race pads), each bed-in needs to be application-specific. One could try to generate a one-size-fits-all procedure, but too little heat during bed-in keeps the material from transferring to the rotor face while overheating the system can generate uneven pad deposits due to the material breaking down and splotching (that's a technical term) on to the rotor face.
In summary, the key to a successful bed-in is to bring the pads up to their adherent operating temperature in a controlled manner and keep them there long enough to start the pad material transfer process. Different brake system designs, pad types, and driving conditions require different procedures to successfully accomplish the bed-in. The recommended procedures below should provide you with the information you need to select the bed-in procedure appropriate for your application.
...thanks to by Matt Weiss of StopTech and James Walker of scR motorsports!
"Removing the Mystery from Brake Pad Bed-In"
Pad+Rotor_Bed-In_Theory_LINK
In order for any brake system to work optimally, the rotors and pads must be properly bedded-in, period. This process can also be called break-in, conditioning, or burnishing, but whatever terminology you choose, getting the brakes properly bedded-in and keeping them that way is critical to the peak performance of the entire brake system.
However, understanding why the rotors and pads need to be bedded-in is just as important as the actual process. If one understands what is happening during the bed-in process, they can tailor the process to specific pads, rotors, and/or driving conditions. For this reason, we present this generic bed-in overview pertaining to all brake systems, but follow with links to application-specific bed-in procedures to fit most every set of circumstances.
- What is brake pad "bed-in" anyway?
Simply stated, bed-in is the process of depositing an even layer of brake pad material, or transfer layer, on the rubbing surface of the rotor disc. That's it. End of discussion. Ok, not really, but although bed-in is quite basic in definition, achieving this condition in practice can be quite a challenge, and the ramifications of improper or incomplete bed-in can be quite a-a-n-n-o-o-y-y-i-i-n-n-g-g.
- Abrasive friction and adherent friction
There are two basic types of brake pad friction mechanisms: abrasive friction and adherent friction . In general, all pads display a bit of each, with abrasive mechanisms dominating the lower temperature ranges while adherent mechanisms come more into play as pad temperature increases. Both mechanisms allow for friction or the conversion of Kinetic energy to Thermal energy, which is the function of a brake system, by the breaking of molecular bonds in vastly different ways.
The abrasive mechanism generates friction or energy conversion by the mechanical rubbing of the brake pad material directly on the rotor disc. In a crystalline sense, the weaker of the bonds in the two different materials is broken. This obviously results in mechanical wear of both the pad and the rotor. Consequently, both pads and rotors are replaced when they are physically worn to their limit and are too thin to endure further service.
The adherent mechanism is altogether different. In an adherent system, a thin layer of brake pad material actually transfers and sticks (adheres) on to the rotor face. The layer of pad material, once evenly established on the rotor, is what actually rubs on the brake pad. The bonds that are broken, for the conversion of Kinetic to Thermal energy, are formed instantaneously before being broken again. It is this brake pad-on-transferred brake pad material interaction on a molecular level that yields the conversion process.
With the adherent mechanism there is much reduced rotor wear as compared to abrasive mechanism, but it's not a free lunch - pads now become the primary wear element in the braking system. And even though rotors are not mechanically worn down with adherent systems, they still will need to be replaced on a regular basis due to cracking reaching a point of failure if they are exposed to intense, repetitive thermal cycling. This is why race teams throw out rotors that are actually as thick or thicker than when they were brand new. It's due to the an adherent brake pad transfer layer!
- The all-important transfer layer
As stated above, the objective of the bed-in process is to deposit an even layer of brake pad material, or transfer layer , on the rubbing surface of the rotor disc. Note the emphasis on the word even, as uneven pad deposits on the rotor face are the number one, and almost exclusive cause of brake judder or vibration.
Let's say that again, just so there is no misunderstanding. Uneven pad deposits on the rotor face are the number one, and almost exclusive cause of brake judder or vibration.
It only takes a small amount of thickness variation, or TV, in the transfer layer (we're only talking a few ten thousandths of an inch here) to initiate brake vibration. While the impact of an uneven transfer layer is almost imperceptible at first, as the pad starts riding the high and low spots, more and more TV will be naturally generated until the vibration is much more evident. With prolonged exposure, the high spots can become hot spots and can actually change the metallurgy of the rotor in those areas, creating "hard" spots in the rotor face that are virtually impossible to remove.
- Bedding fundamentals
In general, bed-in consists of heating a brake system to its adherent temperature to allow the formation of a transfer layer. The brake system is then allowed to cool without coming to rest, resulting in an even transfer layer deposition around the rotor circumference. This procedure is typically repeated two or three times in order to ensure that the entire rotor face is evenly covered with brake pad material. Sounds easy, right? Well, it can be if you have the proper information.
Because the adherent temperature range for brake pads varies widely (typically 100*F-600*F for street pads and 600*F-1400*F for race pads), each bed-in needs to be application-specific. One could try to generate a one-size-fits-all procedure, but too little heat during bed-in keeps the material from transferring to the rotor face while overheating the system can generate uneven pad deposits due to the material breaking down and splotching (that's a technical term) on to the rotor face.
In summary, the key to a successful bed-in is to bring the pads up to their adherent operating temperature in a controlled manner and keep them there long enough to start the pad material transfer process. Different brake system designs, pad types, and driving conditions require different procedures to successfully accomplish the bed-in. The recommended procedures below should provide you with the information you need to select the bed-in procedure appropriate for your application.
...thanks to by Matt Weiss of StopTech and James Walker of scR motorsports!
Aug 22, 2007 12:29:48 PM
- Boxster Coupe GTS
- Rennteam Master
-
- Loc: UK , United Kingdom
- Posts: 5884, Gallery
- Registered on: Feb 23, 2005
- Reply to: Boxster Coupe GTS
Re: Pad and Rotor Bed-In Theory...
StopTech's Recommended Procedure for Bedding-in Performance Brake Systems
Bedding-in_Performance_Brake_Systems_LINK
When a system has both new rotors and pads, there are two different objectives for bedding-in a performance brake system: heating up the brake rotors and pads in a prescribed manner, so as to transfer pad material evenly onto the rotors; and maturing the pad material, so that resins which are used to bind and form it are 'cooked' out of the pad.
The first objective is achieved by performing a series of stops, so that the brake rotor and pad material are heated steadily to a temperature that promotes the transfer of pad material onto the brake rotor friction surface. There is one pitfall in this process, however, which must be avoided. The rotor and, therefore, the vehicle should not be brought to a complete stop, with the brakes still applied, as this risks the non-uniform transfer of pad material onto the friction surface.
The second objective of the bedding-in process is achieved by performing another set of stops, in order to mature the pad itself. This ensures that resins which are used to bind and form the pad material are 'cooked' out of the pad, at the point where the pad meets the rotor's friction surface.
The bed-in process is not complete until both sets of stops have been performed. There's one exception, however. Some pad manufacturers sell 'race-ready' pads, which have been pre-conditioned by flame heat-treating or laser etching, to provide a mature surface on the pad face. If race-ready pads are being used, then the second set of controlled stops is unnecessary. Also note that the same circumstances exist when a system to be bedded has new rotors and used pads (a strategy that professional teams use to break in their rotors ahead of time) one only has to perform a single set of stops to transfer pad material uniformly onto the new rotor.
Note that, if the brakes of a vehicle with high-performance or racing pads are not used continuously in an aggressive manner, the transfer layer on the rotors can be abraded (literally worn off). However, the transfer layer can be re-established, if needed, by repeating one series of stops in the bed-in procedure. This process may be repeated as often as necessary during the life of the pad.
This characteristic is useful when a system is already bedded-in with one pad friction and another is to be used going forward, like when changing between pad types for the street and track (and then after a track event, back again). The procedure under this case is different, where the new friction is installed and the vehicle is first driven for 5 to 20 miles (8 to 33 Km) with light use, keeping the pad friction and rotor cold. This promotes the abrasive friction mechanism cleaning the rotor surface of the previous pad material before performing either one or two bed-in cycles as prescribed below. One set of stops as outlined, if the pads being installed are used, two if the pads are actually new
The bed-in procedures below outline the steps required to effectively bed-in performance brake systems. We strongly recommend that, in order to complete the bed-in safely, the bed-in procedures be conducted in dry conditions on a race track or other controlled environment, so as not to endanger yourself or others. Please note that we neither recommend nor condone driving at high speeds on public roads. While it is important to get enough heat into the system to effectively bed-in the brakes, it is even more important to exercise common sense at all times, and to conduct the bed-in procedure responsibly.
- Bedding-in Street-Performance Pads
For a typical performance brake system using street-performance pads, a series of ten partial braking events, from 60mph down to 10mph, will typically raise the temperature of the brake components sufficiently to be considered one bed-in set. Each of the ten partial braking events should achieve moderate-to-high deceleration (about 80 to 90% of the deceleration required to lock up the brakes and/or to engage the ABS), and they should be made one after the other, without allowing the brakes to cool in between.
Depending on the make-up of the pad material, the brake friction will seem to gain slightly in performance, and will then lose or fade somewhat by around the fifth stop (also about the time that a friction smell will be detectable in the passenger compartment). This does not indicate that the brakes are bedded-in. This phenomenon is known as a green fade, as it is characteristic of immature or 'green' pads, in which the resins still need to be driven out of the pad material, at the point where the pads meet the rotors. In this circumstance, the upper temperature limit of the friction material will not yet have been reached.
As when bedding-in any set of brakes, care should be taken regarding the longer stopping distance necessary with incompletely bedded pads. This first set of stops in the bed-in process is only complete when all ten stops have been performed - not before. The system should then be allowed to cool, by driving the vehicle at the highest safe speed for the circumstances, without bringing it to a complete stop with the brakes still applied. After cooling the vehicle, a second set of ten partial braking events should be performed, followed by another cooling exercise. In some situations, a third set is beneficial, but two are normally sufficient.
- Bedding-in Club Race or Full Race Pads
For a typical performance brake system using race pads, the bed-in procedure must be somewhat more aggressive, as higher temperatures need to be reached, in order to bring certain brands of pad material up to their full race potential.
We typically recommend a set of ten partial braking events, from 60mph down to 10mph, followed immediately by three or four partial braking events, from 80mph down to 10mph. Alternately, a set of eleven stops, from 80mph to 40mph, or a set of seven stops, from 100mph to 50mph, would be approximately the same. As with street pads, each of the partial braking events should achieve moderate-to-high deceleration (about 80% of the deceleration required to lock up the brakes and/or to engage the ABS), and they should be made one after the other, without allowing the brakes to cool in between.
Again, depending on the make-up of the pad material, the brake friction will seem to gain slightly in performance, and will then lose or fade somewhat about halfway through the first set of stops. This does not indicate that the brakes are bedded-in, except where race-ready pads are being used. This phenomenon is the same as that which occurs with high-performance or street pads (except that, when race-ready pads are used, they do not exhibit green fade, and they will be bedded-in after just one complete set of stops).
As when bedding-in any set of brakes, care should be taken regarding the longer stopping distance necessary with incompletely bedded pads. This first set of stops in the bed-in process is only complete when the recommended number of stops has been performed - not before. As a general rule, it would be better to perform additional stops, than not enough. The system should then be allowed to cool, by driving the vehicle at the highest safe speed for the circumstances, without bringing it to a complete stop with the brakes still applied.
After cooling the vehicle, a second set of the recommended number of stops should be performed, followed by another cooling exercise. In some situations, a third set is beneficial, but two are normally sufficient.
Racers will note that, when a pad is bedded-in properly, there will be approximately 2mm (0.1 inch) of the pad edge near the rotor, on which the paint will have turned to ash, or the color of the pad will have changed to look as though it has been overheated.
In summary, the key to successfully bedding-in performance brakes is to bring the pads up to their operating temperature range, in a controlled manner, and to keep them there long enough to start the pad material transfer process. Different brake system designs, pad types, and driving conditions require different procedures to achieve a successful bed-in. The procedures recommended above should provide a useful starting point for developing bed-in procedures appropriate to individual applications.
...thanks again to by Matt Weiss of StopTech and James Walker of scR motorsports!
Bedding-in_Performance_Brake_Systems_LINK
When a system has both new rotors and pads, there are two different objectives for bedding-in a performance brake system: heating up the brake rotors and pads in a prescribed manner, so as to transfer pad material evenly onto the rotors; and maturing the pad material, so that resins which are used to bind and form it are 'cooked' out of the pad.
The first objective is achieved by performing a series of stops, so that the brake rotor and pad material are heated steadily to a temperature that promotes the transfer of pad material onto the brake rotor friction surface. There is one pitfall in this process, however, which must be avoided. The rotor and, therefore, the vehicle should not be brought to a complete stop, with the brakes still applied, as this risks the non-uniform transfer of pad material onto the friction surface.
The second objective of the bedding-in process is achieved by performing another set of stops, in order to mature the pad itself. This ensures that resins which are used to bind and form the pad material are 'cooked' out of the pad, at the point where the pad meets the rotor's friction surface.
The bed-in process is not complete until both sets of stops have been performed. There's one exception, however. Some pad manufacturers sell 'race-ready' pads, which have been pre-conditioned by flame heat-treating or laser etching, to provide a mature surface on the pad face. If race-ready pads are being used, then the second set of controlled stops is unnecessary. Also note that the same circumstances exist when a system to be bedded has new rotors and used pads (a strategy that professional teams use to break in their rotors ahead of time) one only has to perform a single set of stops to transfer pad material uniformly onto the new rotor.
Note that, if the brakes of a vehicle with high-performance or racing pads are not used continuously in an aggressive manner, the transfer layer on the rotors can be abraded (literally worn off). However, the transfer layer can be re-established, if needed, by repeating one series of stops in the bed-in procedure. This process may be repeated as often as necessary during the life of the pad.
This characteristic is useful when a system is already bedded-in with one pad friction and another is to be used going forward, like when changing between pad types for the street and track (and then after a track event, back again). The procedure under this case is different, where the new friction is installed and the vehicle is first driven for 5 to 20 miles (8 to 33 Km) with light use, keeping the pad friction and rotor cold. This promotes the abrasive friction mechanism cleaning the rotor surface of the previous pad material before performing either one or two bed-in cycles as prescribed below. One set of stops as outlined, if the pads being installed are used, two if the pads are actually new
The bed-in procedures below outline the steps required to effectively bed-in performance brake systems. We strongly recommend that, in order to complete the bed-in safely, the bed-in procedures be conducted in dry conditions on a race track or other controlled environment, so as not to endanger yourself or others. Please note that we neither recommend nor condone driving at high speeds on public roads. While it is important to get enough heat into the system to effectively bed-in the brakes, it is even more important to exercise common sense at all times, and to conduct the bed-in procedure responsibly.
- Bedding-in Street-Performance Pads
For a typical performance brake system using street-performance pads, a series of ten partial braking events, from 60mph down to 10mph, will typically raise the temperature of the brake components sufficiently to be considered one bed-in set. Each of the ten partial braking events should achieve moderate-to-high deceleration (about 80 to 90% of the deceleration required to lock up the brakes and/or to engage the ABS), and they should be made one after the other, without allowing the brakes to cool in between.
Depending on the make-up of the pad material, the brake friction will seem to gain slightly in performance, and will then lose or fade somewhat by around the fifth stop (also about the time that a friction smell will be detectable in the passenger compartment). This does not indicate that the brakes are bedded-in. This phenomenon is known as a green fade, as it is characteristic of immature or 'green' pads, in which the resins still need to be driven out of the pad material, at the point where the pads meet the rotors. In this circumstance, the upper temperature limit of the friction material will not yet have been reached.
As when bedding-in any set of brakes, care should be taken regarding the longer stopping distance necessary with incompletely bedded pads. This first set of stops in the bed-in process is only complete when all ten stops have been performed - not before. The system should then be allowed to cool, by driving the vehicle at the highest safe speed for the circumstances, without bringing it to a complete stop with the brakes still applied. After cooling the vehicle, a second set of ten partial braking events should be performed, followed by another cooling exercise. In some situations, a third set is beneficial, but two are normally sufficient.
- Bedding-in Club Race or Full Race Pads
For a typical performance brake system using race pads, the bed-in procedure must be somewhat more aggressive, as higher temperatures need to be reached, in order to bring certain brands of pad material up to their full race potential.
We typically recommend a set of ten partial braking events, from 60mph down to 10mph, followed immediately by three or four partial braking events, from 80mph down to 10mph. Alternately, a set of eleven stops, from 80mph to 40mph, or a set of seven stops, from 100mph to 50mph, would be approximately the same. As with street pads, each of the partial braking events should achieve moderate-to-high deceleration (about 80% of the deceleration required to lock up the brakes and/or to engage the ABS), and they should be made one after the other, without allowing the brakes to cool in between.
Again, depending on the make-up of the pad material, the brake friction will seem to gain slightly in performance, and will then lose or fade somewhat about halfway through the first set of stops. This does not indicate that the brakes are bedded-in, except where race-ready pads are being used. This phenomenon is the same as that which occurs with high-performance or street pads (except that, when race-ready pads are used, they do not exhibit green fade, and they will be bedded-in after just one complete set of stops).
As when bedding-in any set of brakes, care should be taken regarding the longer stopping distance necessary with incompletely bedded pads. This first set of stops in the bed-in process is only complete when the recommended number of stops has been performed - not before. As a general rule, it would be better to perform additional stops, than not enough. The system should then be allowed to cool, by driving the vehicle at the highest safe speed for the circumstances, without bringing it to a complete stop with the brakes still applied.
After cooling the vehicle, a second set of the recommended number of stops should be performed, followed by another cooling exercise. In some situations, a third set is beneficial, but two are normally sufficient.
Racers will note that, when a pad is bedded-in properly, there will be approximately 2mm (0.1 inch) of the pad edge near the rotor, on which the paint will have turned to ash, or the color of the pad will have changed to look as though it has been overheated.
In summary, the key to successfully bedding-in performance brakes is to bring the pads up to their operating temperature range, in a controlled manner, and to keep them there long enough to start the pad material transfer process. Different brake system designs, pad types, and driving conditions require different procedures to achieve a successful bed-in. The procedures recommended above should provide a useful starting point for developing bed-in procedures appropriate to individual applications.
...thanks again to by Matt Weiss of StopTech and James Walker of scR motorsports!
Aug 22, 2007 9:50:37 PM
- porkernut
- Junior
-
- Loc: UK
- Posts: 85, Gallery
- Registered on: May 30, 2006
- Reply to: Boxster Coupe GTS
Forum
About Rennteam | Help | Terms of use | Privacy Policy | Support | Contact | Imprint | Archive
Powered by
Community
and
