De-Mystifying the Warped Rotors Issue ::LONG READ::
12-27-2004, 06:46 AM
#1
Moderator Alumnus
Thread Starter
Join Date: Jul 2003
Location: Windsor-Quebec corridor
Age: 47
Posts: 7,709
Likes: 0
Received 6 Likes
on
4 Posts
De-Mystifying the Warped Rotors Issue ::LONG READ::
Here is an article I grabbed from StopTech , that I read about 2 or 3 years ago, and really helped me solve my own brake problems at the time with my Accord. With so many people here complaining about the warped discs issue, this may be of some help to you guys.
The "Warped" Brake Disc and Other Myths of the Braking System
By Carroll Smith
Copyright © 2001 all rights reserved StopTech LLC
--------------------------------------------------------------------------------
Myth # 1 – BRAKE JUDDER AND VIBRATION IS CAUSED BY DISCS THAT HAVE BEEN WARPED FROM EXESSIVE HEAT.
The term "warped brake disc" has been in common use in motor racing for decades. When a driver reports a vibration under hard braking, inexperienced crews, after checking for (and not finding) cracks often attribute the vibration to "warped discs". They then measure the disc thickness in various places, find significant variation and the diagnosis is cast in stone.
When disc brakes for high performance cars arrived on the scene we began to hear of "warped brake discs" on road going cars, with the same analyses and diagnoses. Typically, the discs are resurfaced to cure the problem and, equally typically, after a relatively short time the roughness or vibration comes back. Brake roughness has caused a significant number of cars to be bought back by their manufacturers under the "lemon laws". This has been going on for decades now - and, like most things that we have cast in stone, the diagnoses are wrong.
With one qualifier, presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification, in more than 40 years of professional racing, including the Shelby/Ford GT 40s – one of the most intense brake development program in history
- I have never seen a warped brake disc. I have seen lots of cracked discs, discs that had turned into shallow cones at operating temperature because they were mounted rigidly to their attachment bells or top hats, a few where the friction surface had collapsed in the area between straight radial interior vanes, and an untold number of discs with pad material unevenly deposited on the friction surfaces - sometimes visible and more often not.
In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures.
In order to understand what is happening here, we will briefly investigate the nature of the stopping power of the disc brake system.
THE NATURE OF BRAKING FRICTION
Friction is the mechanism that converts dynamic energy into heat. Just as there are two sorts of friction between the tire and the road surface (mechanical gripping of road surface irregularities by the elastic tire compound and transient molecular adhesion between the rubber and the road in which rubber is transferred to the road surface), so there are two very different sorts of braking friction - abrasive friction and adherent friction. Abrasive friction involves the breaking of the crystalline bonds of both the pad material and the cast iron of the disc. The breaking of these bonds generates the heat of friction. In abrasive friction, the bonds between crystals of the pad material (and, to a lesser extent, the disc material) are permanently broken. The harder material wears the softer away (hopefully the disc wears the pad). Pads that function primarily by abrasion have a high wear rate and tend to fade at high temperatures. When these pads reach their effective temperature limit, they will transfer pad material onto the disc face in a random and uneven pattern. It is this "pick up" on the disc face that both causes the thickness variation measured by the technicians and the roughness or vibration under the brakes reported by the drivers.
With adherent friction, some of the pad material diffuses across the interface between the pad and the disc and forms a very thin, uniform layer of pad material on the surface of the disc. As the friction surfaces of both disc and pad then comprise basically the same material, material can now cross the interface in both directions and the bonds break and reform. In fact, with adherent friction between pad and disc, the bonds between pad material and the deposits on the disc are transient in nature - they are continually being broken and some of them are continually reforming.
There is no such thing as pure abrasive or pure adherent friction in braking. With many contemporary pad formulas, the pad material must be abrasive enough to keep the disc surface smooth and clean. As the material can cross the interface, the layer on the disc is constantly renewed and kept uniform - again until the temperature limit of the pad has been exceeded or if the pad and the disc have not been bedded-in completely or properly. In the latter case, if a uniform layer of pad material transferred onto the disc face has not been established during bedding or break-in, spot or uncontrolled transfer of the material can occur when operating at high temperatures. The organic and semi-metallic pads of the past were more abrasive than adherent and were severely temperature limited. All of the current generation of "metallic carbon", racing pads utilize mainly adherent technology as do many of the high end street car pads and they are temperature stable over a much higher range. Unfortunately, there is no free lunch and the ultra high temperature racing pads are ineffective at the low temperatures typically experienced in street use.
Therefore - there is no such thing as an ideal "all around" brake pad. The friction material that is quiet and functions well at relatively low temperatures around town will not stop the car that is driven hard. If you attempt to drive many cars hard with the OEM pads, you will experience pad fade, friction material transfer and fluid boiling - end of discussion. The true racing pad, used under normal conditions will be noisy and will not work well at low temperatures around town.
Ideally, in order to avoid either putting up with squealing brakes that will not stop the car well around town or with pad fade on the track or coming down the mountain at speed, we should change pads before indulging in vigorous automotive exercise. No one does. The question remains, what pads should be used in high performance street cars - relatively low temperature street pads or high temperature race pads? Strangely enough, in my opinion, the answer is a high performance street pad with good low temperature characteristics. The reason is simple: If we are driving really hard and begin to run into trouble, either with pad fade or boiling fluid (or both), the condition(s) comes on gradually enough to allow us to simply modify our driving style to compensate. On the other hand, should an emergency occur when the brakes are cold, the high temperature pad is simply not going to stop the car. As an example, during the mid 1960s, those of us at Shelby American did not drive GT 350 or GT 500 Mustangs as company cars simply because they were equipped with Raybestos M-19 racing pads and none of our wives could push on the brake pedal hard enough to stop the car in normal driving.
Regardless of pad composition, if both disc and pad are not properly broken in, material transfer between the two materials can take place in a random fashion - resulting is uneven deposits and vibration under braking. Similarly, even if the brakes are properly broken, if, when they are very hot or following a single long stop from high speed, the brakes are kept applied after the vehicle comes to a complete stop it is possible to leave a telltale deposit behind that looks like the outline of a pad. This kind of deposit is called pad imprinting and looks like the pad was inked for printing like a stamp and then set on the disc face. It is possible to see the perfect outline of the pad on the disc.
It gets worse. Cast iron is an alloy of iron and silicon in solution interspersed with particles of carbon. At elevated temperatures, inclusions of carbides begin to form in the matrix. In the case of the brake disk, any uneven deposits - standing proud of the disc surface - become hotter than the surrounding metal. Every time that the leading edge of one of the deposits rotates into contact with the pad, the local temperature increases. When this local temperature reaches around 1200 or 1300 degrees F. the cast iron under the deposit begins to transform into cementite (an iron carbide in which three atoms of iron combine with one atom of carbon). Cementite is very hard, very abrasive and is a poor heat sink. If severe use continues the system will enter a self-defeating spiral - the amount and depth of the cementite increases with increasing temperature and so does the brake roughness. Drat!
PREVENTION
There is only one way to prevent this sort of thing - following proper break in procedures for both pad and disc and use the correct pad for your driving style and conditions. All high performance after market discs and pads should come with both installation and break in instructions. The procedures are very similar between manufacturers. With respect to the pads, the bonding resins must be burned off relatively slowly to avoid both fade and uneven deposits. The procedure is several stops of increasing severity with a brief cooling period between them. After the last stop, the system should be allowed to cool to ambient temperature. Typically, a series of ten increasingly hard stops from 60mph to 5 mph with normal acceleration in between should get the job done for a high performance street pad. During pad or disc break-in, do not come to a complete stop, so plan where and when you do this procedure with care and concern for yourself and the safety of others. If you come to a complete stop before the break-in process is completed there is the chance for non-uniform pad material transfer or pad imprinting to take place and the results will be what the whole process is trying to avoid. Game over.
In terms of stop severity, an ABS active stop would typically be around 0.9 G’s and above, depending on the vehicle. What you want to do is stop at a rate around 0.7 to 0.9 G's. That is a deceleration rate near but below lock up or ABS intervention. You should begin to smell pads at the 5th to 7th stop and the smell should diminish before the last stop. A powdery gray area will become visible on the edge of the pad (actually the edge of the friction material in contact with the disc - not the backing plate) where the paint and resins of the pad are burning off. When the gray area on the edges of the pads are about 1/8" deep, the pad is bedded.
For a race pad, typically four 80mph to 5 and two 100mph to 5, depending on the pad, will also be necessary to raise the system temperatures during break-in to the range that the pad material was designed to operate at. Hence, the higher temperature material can establish its layer completely and uniformly on the disc surface.
Fortunately the procedure is also good for the discs and will relieve any residual thermal stresses left over from the casting process (all discs should be thermally stress relieved as one of the last manufacturing processes) and will transfer the smooth layer of pad material onto the disc. If possible, new discs should be bedded with used pads of the same compound that will be used going forward. Again, heat should be put into the system gradually - increasingly hard stops with cool off time in between. Part of the idea is to avoid prolonged contact between pad and disc. With abrasive pads (which should not be used on high performance cars) the disc can be considered bedded when the friction surfaces have attained an even blue color. With the carbon metallic type pads, bedding is complete when the friction surfaces of the disc are a consistent gray or black. In any case, the discoloration of a completely broken in disc will be complete and uniform.
Depending upon the friction compound, easy use of the brakes for an extended period may lead to the removal of the transfer layer on the discs by the abrasive action of the pads. When we are going to exercise a car that has seen easy brake use for a while, a partial re-bedding process will prevent uneven pick up.
The driver can feel a 0.0004" deposit or TV on the disc. 0.001" is annoying. More than that becomes a real pain. When deposit are present, by having isolated regions that are proud of the surface and running much hotter than their neighbors, cementite inevitably forms and the local wear characteristics change which results in ever increasing TV and roughness.
Other than proper break in, as mentioned above, never leave your foot on the brake pedal after you have used the brakes hard. This is not usually a problem on public roads simply because, under normal conditions, the brakes have time to cool before you bring the car to a stop (unless, like me, you live at the bottom of a long steep hill). In any kind of racing, including autocross and "driving days" it is crucial. Regardless of friction material, clamping the pads to a hot stationary disc will result in material transfer and discernible "brake roughness". What is worse, the pad will leave the telltale imprint or outline on the disc and your sin will be visible to all and sundry.
The obvious question now is "is there a "cure" for discs with uneven friction material deposits?" The answer is a conditional yes. If the vibration has just started, the chances are that the temperature has never reached the point where cementite begins to form. In this case, simply fitting a set of good "semi-metallic" pads and using them hard (after bedding) may well remove the deposits and restore the system to normal operation but with upgraded pads. If only a small amount of material has been transferred i.e. if the vibration is just starting, vigorous scrubbing with garnet paper may remove the deposit. As many deposits are not visible, scrub the entire friction surfaces thoroughly. Do not use regular sand paper or emery cloth as the aluminum oxide abrasive material will permeate the cast iron surface and make the condition worse. Do not bead blast or sand blast the discs for the same reason.
The only fix for extensive uneven deposits involves dismounting the discs and having them Blanchard ground - not expensive, but inconvenient at best. A newly ground disc will require the same sort of bedding in process as a new disc. The trouble with this procedure is that if the grinding does not remove all of the cementite inclusions, as the disc wears the hard cementite will stand proud of the relatively soft disc and the thermal spiral starts over again. Unfortunately, the cementite is invisible to the naked eye.
Taking time to properly bed your braking system pays big dividends but, as with most sins, a repeat of the behavior that caused the trouble will bring it right back.
MYTH # 2 - RACING BRAKE DISCS ARE MADE FROM STEEL
To digress for a moment "steel discs" are a misnomer frequently used by people who should know better. This group includes TV commentators and drivers being interviewed. Except for some motorcycles and karts, all ferrous discs are made from cast iron - an excellent material for the job. While steel has a higher tensile strength, cast iron is many times stronger than disc brake requirements. Its thermal transfer characteristics are significantly better than those of steel so that the heat generated at the interface between pad and disc is efficiently carried through the friction faces to the interior surface of the disc and into the vanes from where the heat is dissipated into the air stream. Cast iron is more dimensionally stable at elevated temperature than steel and is a better heat sink - so let us hear no more talk of "steel" brake discs.
MYTH # 3 - A SOFT BRAKE PEDAL IS THE RESULT OF PAD FADE
The all too familiar mushy brake pedal is caused by overheated brake fluid, not overheated pads. Repeated heavy use of the brakes may lead to "brake fade". There are two distinct varieties of brake fade
A) When the temperature at the interface between the pad and the rotor exceeds the thermal capacity of the pad, the pad loses friction capability due largely to out gassing of the binding agents in the pad compound. The brake pedal remains firm and solid but the car will not stop. The first indication is a distinctive and unpleasant smell which should serve as a warning to back off,
B) When the fluid boils in the calipers air bubbles are formed. Since air is compressible, the brake pedal becomes soft and "mushy" and pedal travel increases. You can probably still stop the car by pumping the pedal but efficient modulation is gone. This is a gradual process with lots of warning.
Comment added by sauceman: For the record, I have 140,000km on my TSX, I have always followed these principles with my TSX, and I still have the stock rotors on, with absolutely no hopping, warping or vibration of any kind to them. This article also helped solving my previous problems with my Accords. Which is why I believe this article has a lot of credibility to it.
The "Warped" Brake Disc and Other Myths of the Braking System
By Carroll Smith
Copyright © 2001 all rights reserved StopTech LLC
--------------------------------------------------------------------------------
Myth # 1 – BRAKE JUDDER AND VIBRATION IS CAUSED BY DISCS THAT HAVE BEEN WARPED FROM EXESSIVE HEAT.
The term "warped brake disc" has been in common use in motor racing for decades. When a driver reports a vibration under hard braking, inexperienced crews, after checking for (and not finding) cracks often attribute the vibration to "warped discs". They then measure the disc thickness in various places, find significant variation and the diagnosis is cast in stone.
When disc brakes for high performance cars arrived on the scene we began to hear of "warped brake discs" on road going cars, with the same analyses and diagnoses. Typically, the discs are resurfaced to cure the problem and, equally typically, after a relatively short time the roughness or vibration comes back. Brake roughness has caused a significant number of cars to be bought back by their manufacturers under the "lemon laws". This has been going on for decades now - and, like most things that we have cast in stone, the diagnoses are wrong.
With one qualifier, presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification, in more than 40 years of professional racing, including the Shelby/Ford GT 40s – one of the most intense brake development program in history
- I have never seen a warped brake disc. I have seen lots of cracked discs, discs that had turned into shallow cones at operating temperature because they were mounted rigidly to their attachment bells or top hats, a few where the friction surface had collapsed in the area between straight radial interior vanes, and an untold number of discs with pad material unevenly deposited on the friction surfaces - sometimes visible and more often not.
In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures.
In order to understand what is happening here, we will briefly investigate the nature of the stopping power of the disc brake system.
THE NATURE OF BRAKING FRICTION
Friction is the mechanism that converts dynamic energy into heat. Just as there are two sorts of friction between the tire and the road surface (mechanical gripping of road surface irregularities by the elastic tire compound and transient molecular adhesion between the rubber and the road in which rubber is transferred to the road surface), so there are two very different sorts of braking friction - abrasive friction and adherent friction. Abrasive friction involves the breaking of the crystalline bonds of both the pad material and the cast iron of the disc. The breaking of these bonds generates the heat of friction. In abrasive friction, the bonds between crystals of the pad material (and, to a lesser extent, the disc material) are permanently broken. The harder material wears the softer away (hopefully the disc wears the pad). Pads that function primarily by abrasion have a high wear rate and tend to fade at high temperatures. When these pads reach their effective temperature limit, they will transfer pad material onto the disc face in a random and uneven pattern. It is this "pick up" on the disc face that both causes the thickness variation measured by the technicians and the roughness or vibration under the brakes reported by the drivers.
With adherent friction, some of the pad material diffuses across the interface between the pad and the disc and forms a very thin, uniform layer of pad material on the surface of the disc. As the friction surfaces of both disc and pad then comprise basically the same material, material can now cross the interface in both directions and the bonds break and reform. In fact, with adherent friction between pad and disc, the bonds between pad material and the deposits on the disc are transient in nature - they are continually being broken and some of them are continually reforming.
There is no such thing as pure abrasive or pure adherent friction in braking. With many contemporary pad formulas, the pad material must be abrasive enough to keep the disc surface smooth and clean. As the material can cross the interface, the layer on the disc is constantly renewed and kept uniform - again until the temperature limit of the pad has been exceeded or if the pad and the disc have not been bedded-in completely or properly. In the latter case, if a uniform layer of pad material transferred onto the disc face has not been established during bedding or break-in, spot or uncontrolled transfer of the material can occur when operating at high temperatures. The organic and semi-metallic pads of the past were more abrasive than adherent and were severely temperature limited. All of the current generation of "metallic carbon", racing pads utilize mainly adherent technology as do many of the high end street car pads and they are temperature stable over a much higher range. Unfortunately, there is no free lunch and the ultra high temperature racing pads are ineffective at the low temperatures typically experienced in street use.
Therefore - there is no such thing as an ideal "all around" brake pad. The friction material that is quiet and functions well at relatively low temperatures around town will not stop the car that is driven hard. If you attempt to drive many cars hard with the OEM pads, you will experience pad fade, friction material transfer and fluid boiling - end of discussion. The true racing pad, used under normal conditions will be noisy and will not work well at low temperatures around town.
Ideally, in order to avoid either putting up with squealing brakes that will not stop the car well around town or with pad fade on the track or coming down the mountain at speed, we should change pads before indulging in vigorous automotive exercise. No one does. The question remains, what pads should be used in high performance street cars - relatively low temperature street pads or high temperature race pads? Strangely enough, in my opinion, the answer is a high performance street pad with good low temperature characteristics. The reason is simple: If we are driving really hard and begin to run into trouble, either with pad fade or boiling fluid (or both), the condition(s) comes on gradually enough to allow us to simply modify our driving style to compensate. On the other hand, should an emergency occur when the brakes are cold, the high temperature pad is simply not going to stop the car. As an example, during the mid 1960s, those of us at Shelby American did not drive GT 350 or GT 500 Mustangs as company cars simply because they were equipped with Raybestos M-19 racing pads and none of our wives could push on the brake pedal hard enough to stop the car in normal driving.
Regardless of pad composition, if both disc and pad are not properly broken in, material transfer between the two materials can take place in a random fashion - resulting is uneven deposits and vibration under braking. Similarly, even if the brakes are properly broken, if, when they are very hot or following a single long stop from high speed, the brakes are kept applied after the vehicle comes to a complete stop it is possible to leave a telltale deposit behind that looks like the outline of a pad. This kind of deposit is called pad imprinting and looks like the pad was inked for printing like a stamp and then set on the disc face. It is possible to see the perfect outline of the pad on the disc.
It gets worse. Cast iron is an alloy of iron and silicon in solution interspersed with particles of carbon. At elevated temperatures, inclusions of carbides begin to form in the matrix. In the case of the brake disk, any uneven deposits - standing proud of the disc surface - become hotter than the surrounding metal. Every time that the leading edge of one of the deposits rotates into contact with the pad, the local temperature increases. When this local temperature reaches around 1200 or 1300 degrees F. the cast iron under the deposit begins to transform into cementite (an iron carbide in which three atoms of iron combine with one atom of carbon). Cementite is very hard, very abrasive and is a poor heat sink. If severe use continues the system will enter a self-defeating spiral - the amount and depth of the cementite increases with increasing temperature and so does the brake roughness. Drat!
PREVENTION
There is only one way to prevent this sort of thing - following proper break in procedures for both pad and disc and use the correct pad for your driving style and conditions. All high performance after market discs and pads should come with both installation and break in instructions. The procedures are very similar between manufacturers. With respect to the pads, the bonding resins must be burned off relatively slowly to avoid both fade and uneven deposits. The procedure is several stops of increasing severity with a brief cooling period between them. After the last stop, the system should be allowed to cool to ambient temperature. Typically, a series of ten increasingly hard stops from 60mph to 5 mph with normal acceleration in between should get the job done for a high performance street pad. During pad or disc break-in, do not come to a complete stop, so plan where and when you do this procedure with care and concern for yourself and the safety of others. If you come to a complete stop before the break-in process is completed there is the chance for non-uniform pad material transfer or pad imprinting to take place and the results will be what the whole process is trying to avoid. Game over.
In terms of stop severity, an ABS active stop would typically be around 0.9 G’s and above, depending on the vehicle. What you want to do is stop at a rate around 0.7 to 0.9 G's. That is a deceleration rate near but below lock up or ABS intervention. You should begin to smell pads at the 5th to 7th stop and the smell should diminish before the last stop. A powdery gray area will become visible on the edge of the pad (actually the edge of the friction material in contact with the disc - not the backing plate) where the paint and resins of the pad are burning off. When the gray area on the edges of the pads are about 1/8" deep, the pad is bedded.
For a race pad, typically four 80mph to 5 and two 100mph to 5, depending on the pad, will also be necessary to raise the system temperatures during break-in to the range that the pad material was designed to operate at. Hence, the higher temperature material can establish its layer completely and uniformly on the disc surface.
Fortunately the procedure is also good for the discs and will relieve any residual thermal stresses left over from the casting process (all discs should be thermally stress relieved as one of the last manufacturing processes) and will transfer the smooth layer of pad material onto the disc. If possible, new discs should be bedded with used pads of the same compound that will be used going forward. Again, heat should be put into the system gradually - increasingly hard stops with cool off time in between. Part of the idea is to avoid prolonged contact between pad and disc. With abrasive pads (which should not be used on high performance cars) the disc can be considered bedded when the friction surfaces have attained an even blue color. With the carbon metallic type pads, bedding is complete when the friction surfaces of the disc are a consistent gray or black. In any case, the discoloration of a completely broken in disc will be complete and uniform.
Depending upon the friction compound, easy use of the brakes for an extended period may lead to the removal of the transfer layer on the discs by the abrasive action of the pads. When we are going to exercise a car that has seen easy brake use for a while, a partial re-bedding process will prevent uneven pick up.
The driver can feel a 0.0004" deposit or TV on the disc. 0.001" is annoying. More than that becomes a real pain. When deposit are present, by having isolated regions that are proud of the surface and running much hotter than their neighbors, cementite inevitably forms and the local wear characteristics change which results in ever increasing TV and roughness.
Other than proper break in, as mentioned above, never leave your foot on the brake pedal after you have used the brakes hard. This is not usually a problem on public roads simply because, under normal conditions, the brakes have time to cool before you bring the car to a stop (unless, like me, you live at the bottom of a long steep hill). In any kind of racing, including autocross and "driving days" it is crucial. Regardless of friction material, clamping the pads to a hot stationary disc will result in material transfer and discernible "brake roughness". What is worse, the pad will leave the telltale imprint or outline on the disc and your sin will be visible to all and sundry.
The obvious question now is "is there a "cure" for discs with uneven friction material deposits?" The answer is a conditional yes. If the vibration has just started, the chances are that the temperature has never reached the point where cementite begins to form. In this case, simply fitting a set of good "semi-metallic" pads and using them hard (after bedding) may well remove the deposits and restore the system to normal operation but with upgraded pads. If only a small amount of material has been transferred i.e. if the vibration is just starting, vigorous scrubbing with garnet paper may remove the deposit. As many deposits are not visible, scrub the entire friction surfaces thoroughly. Do not use regular sand paper or emery cloth as the aluminum oxide abrasive material will permeate the cast iron surface and make the condition worse. Do not bead blast or sand blast the discs for the same reason.
The only fix for extensive uneven deposits involves dismounting the discs and having them Blanchard ground - not expensive, but inconvenient at best. A newly ground disc will require the same sort of bedding in process as a new disc. The trouble with this procedure is that if the grinding does not remove all of the cementite inclusions, as the disc wears the hard cementite will stand proud of the relatively soft disc and the thermal spiral starts over again. Unfortunately, the cementite is invisible to the naked eye.
Taking time to properly bed your braking system pays big dividends but, as with most sins, a repeat of the behavior that caused the trouble will bring it right back.
MYTH # 2 - RACING BRAKE DISCS ARE MADE FROM STEEL
To digress for a moment "steel discs" are a misnomer frequently used by people who should know better. This group includes TV commentators and drivers being interviewed. Except for some motorcycles and karts, all ferrous discs are made from cast iron - an excellent material for the job. While steel has a higher tensile strength, cast iron is many times stronger than disc brake requirements. Its thermal transfer characteristics are significantly better than those of steel so that the heat generated at the interface between pad and disc is efficiently carried through the friction faces to the interior surface of the disc and into the vanes from where the heat is dissipated into the air stream. Cast iron is more dimensionally stable at elevated temperature than steel and is a better heat sink - so let us hear no more talk of "steel" brake discs.
MYTH # 3 - A SOFT BRAKE PEDAL IS THE RESULT OF PAD FADE
The all too familiar mushy brake pedal is caused by overheated brake fluid, not overheated pads. Repeated heavy use of the brakes may lead to "brake fade". There are two distinct varieties of brake fade
A) When the temperature at the interface between the pad and the rotor exceeds the thermal capacity of the pad, the pad loses friction capability due largely to out gassing of the binding agents in the pad compound. The brake pedal remains firm and solid but the car will not stop. The first indication is a distinctive and unpleasant smell which should serve as a warning to back off,
B) When the fluid boils in the calipers air bubbles are formed. Since air is compressible, the brake pedal becomes soft and "mushy" and pedal travel increases. You can probably still stop the car by pumping the pedal but efficient modulation is gone. This is a gradual process with lots of warning.
Comment added by sauceman: For the record, I have 140,000km on my TSX, I have always followed these principles with my TSX, and I still have the stock rotors on, with absolutely no hopping, warping or vibration of any kind to them. This article also helped solving my previous problems with my Accords. Which is why I believe this article has a lot of credibility to it.
01-11-2005, 07:37 PM
#6
Banned
Sauceman, it is probably because you do a lot of highway miles and my guess is that automatic cars are more affected. My Accord was the first car I experimented rotor warping. I changed them at 140000km but they were pulsating since a long time. I also had a wheel bearing problem and it is hard to determine which caused which.
01-11-2005, 10:25 PM
#7
I am not quite ready to give up the notion that rotors warp. High temperatures do make many metals more ductile and "distoratable." Furthermore, I am not under the inclination that high heat alone is the culprit to warping. I think that rapid changes in heat are contributors as well.
Why do I think rotors warp? Because in my line of work, I have actually turned brake rotors with a lathe. On the outer face of the rotor, many times I noticed an area around the face that was higher than the rest of the face. Likewise, I also noticed on many badly warped rotors a corresponing low spot on the inner face of the rotor. So, basically, Mr. Smith is saying that buildup can occur on one area of the rotor on the outside, but on the inside it occurs all the way around the rotor except the spot that corresponds to the one on the outside? A more likely notion in my mind is that the rotor had warped significantly in that area, where a "wrinkle" occured. Whether or not heat alone causes this symptom I don't know, but heat making the rotor more suceptable to distortion plays a fair role!
This is not to say that pad deposits are not the cause for many-a brake shimmy. I just think tossing out warping all together is not reasonable.
Secondly, I do not agree that turning rotors is not a fix for brake shimmy. Conditions like hot-spotting and cracking and discoloration are all unfixable and render a rotor garbage. A brake shimmy IS permenantly repairable by machining the rotor. I tend to think more realistically when I feel that (and I said this before on this board) the primary causes of brake shimmy are:
1)Pad and brake combination/size is not up to snuff.
2)Your driving style is not up to snuff.
Simply resurfacing the rotor and putting similar or inferior pads on will only repeat or increase the problem. Likewise, putting new good parts on can be eaily ruined by someone with inferior braking practices. Through numerous personal experiences of my own, I feel wholeheartedly on this issue. One way or another, upgrading your setup will likely solve your problem. More of us are inclinded to spend money on our cars than learn how to drive them better.
So my tips to avoid brake problems, consider that pads make a big difference in brake performance and feel. Consider your driving style. And consider the fact that "I want a pad that makes no dust, no noise, stops on a dime, every time, never warps, and smells pretty when they get up to temps" is rediculous. Finding pads that meet ALL the demands is not alway possible. You can't buy one pair of shoes that you can wear to dinner, to work, to the beach, to the mountains, to the gym, and to keep your toes toasty while making Folgers and expect optimum performance no matter what the condition, can you? Many customers want some imaginary part that does everything. This is the source of much of the bitching that occurs online. Thus, I choose not to give so much credit to those who complain a lot. I think we all can agree that internet folk are never short of something to bitch about!
On the subject of breaking in, I agree that doing it right is of the utmost importance. His descriptions how to do it properly seem agreeable. Sounds like what I do. Although I will add that being ANAL here is not necessarly.
Yes, rotors are iron, but not all iron is created the same. Rotor formulation is not as big of and issue as pad formulation, but if you find a rotor with a better iron alloy, it is likely to perform better.
And just because sauceman has never warped rotors does not give the article full credibility. We don't know much about his driving style, commute, or really anything else about him.....one person mentioned he drive high freeway miles. Well, that is not a surprise he has not brake problems then.
Why do I think rotors warp? Because in my line of work, I have actually turned brake rotors with a lathe. On the outer face of the rotor, many times I noticed an area around the face that was higher than the rest of the face. Likewise, I also noticed on many badly warped rotors a corresponing low spot on the inner face of the rotor. So, basically, Mr. Smith is saying that buildup can occur on one area of the rotor on the outside, but on the inside it occurs all the way around the rotor except the spot that corresponds to the one on the outside? A more likely notion in my mind is that the rotor had warped significantly in that area, where a "wrinkle" occured. Whether or not heat alone causes this symptom I don't know, but heat making the rotor more suceptable to distortion plays a fair role!
This is not to say that pad deposits are not the cause for many-a brake shimmy. I just think tossing out warping all together is not reasonable.
Secondly, I do not agree that turning rotors is not a fix for brake shimmy. Conditions like hot-spotting and cracking and discoloration are all unfixable and render a rotor garbage. A brake shimmy IS permenantly repairable by machining the rotor. I tend to think more realistically when I feel that (and I said this before on this board) the primary causes of brake shimmy are:
1)Pad and brake combination/size is not up to snuff.
2)Your driving style is not up to snuff.
Simply resurfacing the rotor and putting similar or inferior pads on will only repeat or increase the problem. Likewise, putting new good parts on can be eaily ruined by someone with inferior braking practices. Through numerous personal experiences of my own, I feel wholeheartedly on this issue. One way or another, upgrading your setup will likely solve your problem. More of us are inclinded to spend money on our cars than learn how to drive them better.
So my tips to avoid brake problems, consider that pads make a big difference in brake performance and feel. Consider your driving style. And consider the fact that "I want a pad that makes no dust, no noise, stops on a dime, every time, never warps, and smells pretty when they get up to temps" is rediculous. Finding pads that meet ALL the demands is not alway possible. You can't buy one pair of shoes that you can wear to dinner, to work, to the beach, to the mountains, to the gym, and to keep your toes toasty while making Folgers and expect optimum performance no matter what the condition, can you? Many customers want some imaginary part that does everything. This is the source of much of the bitching that occurs online. Thus, I choose not to give so much credit to those who complain a lot. I think we all can agree that internet folk are never short of something to bitch about!
On the subject of breaking in, I agree that doing it right is of the utmost importance. His descriptions how to do it properly seem agreeable. Sounds like what I do. Although I will add that being ANAL here is not necessarly.
Yes, rotors are iron, but not all iron is created the same. Rotor formulation is not as big of and issue as pad formulation, but if you find a rotor with a better iron alloy, it is likely to perform better.
And just because sauceman has never warped rotors does not give the article full credibility. We don't know much about his driving style, commute, or really anything else about him.....one person mentioned he drive high freeway miles. Well, that is not a surprise he has not brake problems then.
Trending Topics
01-11-2005, 10:44 PM
#8
Moderator Alumnus
Thread Starter
Join Date: Jul 2003
Location: Windsor-Quebec corridor
Age: 47
Posts: 7,709
Likes: 0
Received 6 Likes
on
4 Posts
Originally Posted by MrHeeltoe
And just because sauceman has never warped rotors does not give the article full credibility. We don't know much about his driving style, commute, or really anything else about him.....one person mentioned he drive high freeway miles. Well, that is not a surprise he has not brake problems then.
If you don't know me, it's not my problem. I post here enough, and tell enough about myself for anyone here who reads the threads just a little to have a clue about who sauceman is. I don't see YOU popping in here too often, so keep those comments to yourself!
And I didn't say I never warped or had any rotor issue. In fact, I cracked a few sets of discs, had my rotors on my previous Accords, OEM or not resurfaced more often than I can count them, and I got so sick of those problems that I actually decided to study the whole deal to see where the problem was, only to find out that the problem was ME. Hell, I even blew both of my front brake lines at the same time once, nearly killing myself in the process.
As soon as I learned how to use my brakes properly, I then stopped having problems with my brakes. I now have 141,000km to the odo on my TSX, and I haven't resurfaced my rotors yet, and I am not soon to be in the need to, because I don't feel a hint of a vibration when I brake. If anything, I'd call that a positive experience, and so, seeing all of the members who've had issues with their brakes on their TSX, given that I have the most mileage on a TSX here, I thought I could at least contribute that much with this article that helped me a lot personally.
I agree with much of what you've said, because it is along the lines of what I've learned myself. If you can bring more insight, I'd be glad to learn from you as well, I just have a hard time understanding why you would want to put me to doubt, I don't believe I've attacked you.
01-12-2005, 04:41 AM
#9
Race Director
sauce, take it easy on the guy - he made a good contribution.
I'd venture to guess that few folks, even after reading this thread, would follow through to actually change their driving behavior to eliminate potential problems. Kinda like sticking to a diet....
Biker, who would be one of those who probably couldn't change driving habits.
I'd venture to guess that few folks, even after reading this thread, would follow through to actually change their driving behavior to eliminate potential problems. Kinda like sticking to a diet....
Biker, who would be one of those who probably couldn't change driving habits.
01-12-2005, 11:18 AM
#10
Banned
And I should add that most of cars that suffers from brakes warping is because of a bad design right at the start. There are cars that warping is non-existent.
My old Scirocco at 130000 miles wouldn't stop anymore. Why? Because all rotors became too thin with the old pads! You rarely see this today.
Recent Toyota have much better brakes than Hondas.
My old Scirocco at 130000 miles wouldn't stop anymore. Why? Because all rotors became too thin with the old pads! You rarely see this today.
Recent Toyota have much better brakes than Hondas.
01-12-2005, 11:48 AM
#11
I agree with much of what you've said, because it is along the lines of what I've learned myself. If you can bring more insight, I'd be glad to learn from you as well, I just have a hard time understanding why you would want to put me to doubt, I don't believe I've attacked you.
If you don't know me, it's not my problem. I post here enough, and tell enough about myself for anyone here who reads the threads just a little to have a clue about who sauceman is. I don't see YOU popping in here too often, so keep those comments to yourself!
If you don't know me, it's not my problem. I post here enough, and tell enough about myself for anyone here who reads the threads just a little to have a clue about who sauceman is. I don't see YOU popping in here too often, so keep those comments to yourself!
I know I don't post a lot, but that is because I search instead of posting. The common double edged sword is that if you post without searching you get FLAMED, and if you always search and hardly post you have low post count and less creditbility. So basically, I post when I see something worth posting to. I assume nothing but what I read.
And I UNDERSTAND FULLY your stance now in agreeance with myself. I think you did exactly the right thing by considering your driving style could be modified. SO many people are uneducated, unskilled, overconfident, and egotistical about their driving and have the audacity to blame the car! I am not excluded, and have learned many hard lessons in my relatively short driving career. You have appeared to have learned as well and have qualified yourself with the amount of reason to modify your car. The trend of people making poor driving habits with expensive parts is not helping out anyone and is basically a danger to us all.
In rereading you post I can see the inflection in your post being that of an informative help to other TSXers. That is great, and I only felt obligated to present my opinion on the matter. I think the Myths he is dispelling are not really myths, because I have never actually heard any of them before. Or maybe they are myths in a higher or lower automotive status than I generally mingle with...who knows.
If I think of anything else I will post
For now, I am assembling a number of technical documents myself of HOW CARS WORK. This article will be greatly helpful in my "brakes" chapter. I will bookmark this thread. This is aritcle holds a lot of information that I did not know about and I feel like my brain got a little bigger after reading it. Who knows. One day my work might be done.
01-12-2005, 02:01 PM
#13
Über Geek
Join Date: Jul 2003
Location: Gator Country
Posts: 932
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by MrHeeltoe
I know I don't post a lot, but that is because I search instead of posting. The common double edged sword is that if you post without searching you get FLAMED, and if you always search and hardly post you have low post count and less creditbility. So basically, I post when I see something worth posting to. I assume nothing but what I read.
And I UNDERSTAND FULLY your stance now in agreeance with myself…
In rereading you post I can see the inflection in your post being that of an informative help to other TSXers. That is great, and I only felt obligated to present my opinion on the matter. I think the Myths he is dispelling are not really myths, because I have never actually heard any of them before. Or maybe they are myths in a higher or lower automotive status than I generally mingle with...who knows.
And I UNDERSTAND FULLY your stance now in agreeance with myself…
In rereading you post I can see the inflection in your post being that of an informative help to other TSXers. That is great, and I only felt obligated to present my opinion on the matter. I think the Myths he is dispelling are not really myths, because I have never actually heard any of them before. Or maybe they are myths in a higher or lower automotive status than I generally mingle with...who knows.
1) Sauceman's seniority and post count DO matter. As someone here from the start (July '03) I'll vouch for his opinions holding water. Please see his treatise on squeezing out insane mileage figures.
2) The article's author seems to know his shit too.
3) No such word as "agreeance" despite voice-of-a-generation Fred Durst's useage.
4) By all means, present your opinions. They are the fuel of a forum. Just don't be an ass about it.
To prove that I call them as I see them, I really liked YOUR post/thread about rotors vs. pads.
01-12-2005, 04:04 PM
#14
Moderator Alumnus
Thread Starter
Join Date: Jul 2003
Location: Windsor-Quebec corridor
Age: 47
Posts: 7,709
Likes: 0
Received 6 Likes
on
4 Posts
Originally Posted by jiggaman
i think the whole MOD thing is going to sauces head...
just kidding ofcourse
just kidding ofcourse
I promise I'll try and be in a better mood or not post..
01-12-2005, 04:17 PM
#15
Moderator Alumnus
Thread Starter
Join Date: Jul 2003
Location: Windsor-Quebec corridor
Age: 47
Posts: 7,709
Likes: 0
Received 6 Likes
on
4 Posts
Originally Posted by MrHeeltoe
Hold the phone turbo. Sorry, I was not trying to offend you. BUT. You posted an article and offered no interpretation. The only comment added was that you had placed your support in favor of it without indicating exception, and a general one at that. In all honesty, I DON'T know you. And actually, a common misconception on the internet is that it is not your problem. Indeed, it IS your problem. You see, when you submit an article with clear opinions, and offer no opinion of your own in support or opposition, those opinions are naturally presented to be yours as well. It is your responsibility as the poster to clarify your stance so as to avoid being misunderstood. Sorry to break it to you, but another common misconception is that post count or moderator status provides creditbility. Maybe in your case it does, but it is not a rule.
At any rate, if there was something I had found not to be true through my own experience, I would have either not posted it at all, or written a counter-opinion myself in order for it to be clear that it was not MY opinion. Without an afterthought.
As for the status, I really feel I shouldn't be bringing this up. It's not why I'm a mod, and if that was the reason, I'd best resign right away. I'm here to help, it's all that matters, because I myself have benefitted a lot from this site.
01-12-2005, 05:30 PM
#16
Regardless, I think my comments were patially mistyped and partially misinterpreted. Likewise I misinterpreted your intentions with the presentation of the article. One way or another I agree with alot of what the article has to say. I am not trying to get into a pissing match to see who is right and not and whatever.
If I am being a jerk, again, sorry. Not trying to.
And on the issue of creditbility I left it open-ended Uber geek, erm, captainjack. I am not saying anything bad about saucy or anyone else. I am not going to retype what I already said. In not appending the article I felt sacueman agreed with the article without exception. Clearly he does not. Sauceman believes that warping can happen, and so do I, and I just wanted to clarify that.
Everybody relax the panties.
If I am being a jerk, again, sorry. Not trying to.
And on the issue of creditbility I left it open-ended Uber geek, erm, captainjack. I am not saying anything bad about saucy or anyone else. I am not going to retype what I already said. In not appending the article I felt sacueman agreed with the article without exception. Clearly he does not. Sauceman believes that warping can happen, and so do I, and I just wanted to clarify that.
Everybody relax the panties.
01-13-2005, 04:01 PM
#18
Über Geek
Join Date: Jul 2003
Location: Gator Country
Posts: 932
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by MrHeeltoe
My bad. In all honesty, you know what I mean, and what word would have been appropriate? That's what popped into my head.
Course I knew, I was just busting your chops. No harm, no foul.
01-16-2005, 09:16 AM
#20
Moderator Alumnus
Thread Starter
Join Date: Jul 2003
Location: Windsor-Quebec corridor
Age: 47
Posts: 7,709
Likes: 0
Received 6 Likes
on
4 Posts
Originally Posted by Bizzenn
Does Anyone Know If The Brakes Are Under Warranty For 12 Months 0r 12000 Miles?
01-17-2005, 04:31 AM
#22
Moderator Alumnus
Thread Starter
Join Date: Jul 2003
Location: Windsor-Quebec corridor
Age: 47
Posts: 7,709
Likes: 0
Received 6 Likes
on
4 Posts
Originally Posted by Bizzenn
That doesn't really answer my question
You bet!
I don't know the answer. It was my understanding that brakes were included in the bumper-to-bumper warranty, except for wear & tear.
01-17-2005, 03:38 PM
#24
Originally Posted by Bizzenn
Does Anyone Know If The Brakes Are Under Warranty For 12 Months 0r 12000 Miles?
12/12 warranty is the time frame of a typical Honda parts warranty. Basically, they brakes would be covered if they were defective, but generally speaking it is going to be near impossible to prove that pads are defective. Accelerated wear is no indicator of quality, since all cars and drivers are goingt o wear pads at different rates.
Basically, this is true for all maintainance items. Yeah, technically it is under warranty, but really it would not likely ever be honored.
01-22-2005, 03:32 PM
#25
Advanced
Join Date: May 2004
Location: VIVA LAS VEGAS!
Age: 52
Posts: 84
Likes: 0
Received 0 Likes
on
0 Posts
Sauceman,
Phenomenal post! I fwd'd it to my better half, who spends a lot more time tearing apart cars than I do.
Quick off-topic 411: am I reading correctly from your signature that you've achieved 36-46mpg with your TSX? If so, how the hell? I've owned two TSXs (both ATs) and even on long freeway cruises I've been lucky to break 25mpg. In town I barely get 15-16mpg. I love almost everything else about the car, but it's got the worst fuel economy I've ever seen for a car of its weight and engine size ... even my G2 Legend was pulling 20mpg with her 3.2 V6 after 220K miles.
Phenomenal post! I fwd'd it to my better half, who spends a lot more time tearing apart cars than I do.
Quick off-topic 411: am I reading correctly from your signature that you've achieved 36-46mpg with your TSX? If so, how the hell? I've owned two TSXs (both ATs) and even on long freeway cruises I've been lucky to break 25mpg. In town I barely get 15-16mpg. I love almost everything else about the car, but it's got the worst fuel economy I've ever seen for a car of its weight and engine size ... even my G2 Legend was pulling 20mpg with her 3.2 V6 after 220K miles.
01-22-2005, 10:28 PM
#26
Originally Posted by ExHack
Sauceman,
Phenomenal post! I fwd'd it to my better half, who spends a lot more time tearing apart cars than I do.
Quick off-topic 411: am I reading correctly from your signature that you've achieved 36-46mpg with your TSX? If so, how the hell? I've owned two TSXs (both ATs) and even on long freeway cruises I've been lucky to break 25mpg. In town I barely get 15-16mpg. I love almost everything else about the car, but it's got the worst fuel economy I've ever seen for a car of its weight and engine size ... even my G2 Legend was pulling 20mpg with her 3.2 V6 after 220K miles.
Phenomenal post! I fwd'd it to my better half, who spends a lot more time tearing apart cars than I do.
Quick off-topic 411: am I reading correctly from your signature that you've achieved 36-46mpg with your TSX? If so, how the hell? I've owned two TSXs (both ATs) and even on long freeway cruises I've been lucky to break 25mpg. In town I barely get 15-16mpg. I love almost everything else about the car, but it's got the worst fuel economy I've ever seen for a car of its weight and engine size ... even my G2 Legend was pulling 20mpg with her 3.2 V6 after 220K miles.
Maybe there is something wrong with your car. Even with my lead foot we get 20-12 mpg.
01-22-2005, 10:48 PM
#27
Advanced
Join Date: May 2004
Location: VIVA LAS VEGAS!
Age: 52
Posts: 84
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by MrHeeltoe
Maybe there is something wrong with your car. Even with my lead foot we get 20-12 mpg.
Thread
Thread Starter
Forum
Replies
Last Post
