All about brakes and how to prevent warped rotors. (long)
11-30-2001, 09:32 PM
#1
Senior Member
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Join Date: Nov 2001
Posts: 211
All about brakes and how to prevent warped rotors. (long)
A few years ago I had lunch with Hal Baer of Baer Racing (http://www.baer.com) in Arizona, well known for their braking systems. We talked about braking systems in general and got on the subject of rotor warpage,too. I would like to pass on some that very insightful information I learned from them, as well as other info I have gleaned over the years.
Take this info at face value, since you are getting what you payed for it.
Brakes create heat. Duh. That's where most of the stored energy of the moving vehicles goes to when you brake. Rotors absorb, and then dissipate, most of this heat. The more effectively that a braking "system" can store and get rid of this heat, the better the braking system will operate. This mainly depends on two things : rotors and pads.
ROTORS: When braking, the rotors absorb the heat created by the friction from the pads. This heat can get the rotor very hot, over 1000 F for street cars. When this hot rotor touches a brake pad, certain materials in the pad (usually "organic" based) can melt and create gases. These gases can get between the rotor and the pad, effectively causing the pad to "hydroplane" across the surface of the rotor, causing brake fade. As the heat builds, the fade gets worse and the pad is not as effective. This is why slotted and cross drilled rotors can help prevent brake fade, by diminishing this "hydroplaning" from gases, and by letting the rotor be cooler in the first place so that the gases are not created. Then, a rotor must get rid of this heat and cool down. If you take a piece of hot metal and cool it too quickly, it will warp. Remember not to put a hot pan under cold water? Same thing. This is what can cause rotors to warp. If they are hot and they cool too quickly (from water, a puddle, too much cold air) they can warp.
PADS: Pads are a very important part of this equation, more than you may think. There are many different compounds, now with Carbon Fiber, Kevlar, Ceramic, etc. Pads create the stopping power of the vehicle. The most useful compound to us for high performance (and just Street use!) is the Carbon Fiber compounds - more on that later.
Ok, this has been simplistic. Now we look a little harder at the issues. For a brake system to be effetive, it has to generate large amounts of heat AND get rid of that heat. The rotors and pads go through this hot/cold/hot/cold cycle over and over. We can help this scenario in many different ways.
First, we can use larger rotors! The larger rotors will have more metal and surface area for braking, so they can create the same braking forces as smaller rotors, but do it while generating less heat, and have less heat to get rid of. So, the larger the rotor, the better - as long as it fits within your wheels!
Second, we can use rotors that have cooling designs, like venting or slots or cross-drilled. These rotors have more airflow, and may keep the rotor cooler in the first place, helping to prevent the heat build up and the brake fade by not allowing the rotor to get hot enough to create those gasses that cause brake fade. HOWEVER, these cooling systems are not always good. If you have a rotor that is too small for the application to begin with, and you know that it regularly gets very hot, and then it has these cooling systems, it can cool too quickly and warp itself in the process! Especially if you have cooling ducts and very open wheels. Also, these cooling systems reduce the strength of the rotor, and especially venting, reduce the overall MASS of the rotor by eliminating material. So, yes, these cooling systems can actually work against you if the rotor size is insufficient for the application in the first place.
Third, we can use different brake pads. Pads with different compounds are "optimized" to work under certain operating temperature limits, both high and low. So an organic pad may work well from 0 to 350 F, but above that it will quickly fade and melt. Or a ceramic pad may be designed to work between 1000-1500 F, strictly for race use, needing to be "warmed up". The rotors and pads commonly used in Formula 1 get around 3000F and are made from exotic compounds of Kevlar, Ceramic, etc. These are extremes, and our use is in the middle. We will rarely see use above 1000F, even in autocross events. The pads with Carbon Fiber formulas work very well because they can handle these extreme temperatures, but also have a high coefficient of friction so that they grab well under colder temperatures. This is important because for street use, you want your pads to work well when they are cold, such as in a panic stop. You don't always have time to warm them up. Also, they warm up very quickly, and their coefficient of friction actually increases as they get warmer. The classic semi-metallic pads that most cars use these days start to fade around 600-800 F, which is not commonly seen in day-to-day driving, but can easily be seen in spirited driving, or after a few high speed stops. This is when fade comes into play for these pads.
WARPAGE: The Maxima has front wheel drive, so under braking, a lot of the weight shifts forward to the front brakes. The larger a rotor, the less likely it will warp and the better it will perform. HEAT and rapid cooling is the enemy of the rotor. Let's say you do some spirited driving in the twisties and your brakes are getting hot - you can smell them. So, you should pull over and let them cool, right? WRONG! They are already very hot, and the rapid cooling could cause warping. It would actually be better to drive around a while, using the brakes periodically, and let them cool slowly. And if your rotors DO get warped? You take them in and get them turned so that they are now true again. The problem is that they will now be MORE likely to warp again, because by turning the rotors, you grind them down and take off metal which decreases their mass. Those rotors will now be more prone to warping. The more mass to the rotor, the less likely it is to warp. The nice thing about CF compound brake pads is that they wear down the rotors much slower than standard semi-metallic and organic pads (both of which usually have clay as a filler material - yuck). This alone will allow the rotors to maintain as much mass as possible through the years. Also, they work better while creating less heat, so those rotors don't get so hot in the first place. Plus, many compounds are low-dust, which we all would like. And they usually last much longer than standard SM and OR pads for not a whole lot more money. It is standard practice to turn the rotors every time you get the pads replaced, as most shops and dealerships will do. This, in time, gives you thinner and thinner rotors more prone to warping.
Also, overtightening lug nuts (as almost any shop/dealership does) can cause warping of rotors. Over time, the immense forces of the lug nuts combines with the other demands put on the rotor can cause problems. I ALWAYS redo my lugnuts after somebody else has tightened them. IT only takes a second, and they are almost always on too tight.
However, there are some things that can't be prevented. Maybe the rotors that you currently have are of a softer material or a metal that is more prone to warping. On some cars these days, the rotors are very soft and designed to be replaced as often as the brake pads.
Or if you hit that puddle with hot rotors, there is not much you can do about it. And then when you go to get them turned, they will be even more prone to warping. If your wheels are only so big, then only so much rotor will fit inside it.
Also, it is very important for carbon pads to be "bedded" properly, i.e. - broken in. It is proper for a thin, consistent layer of carbon to be transferred to the rotor. If you try to stop too hard too soon without a proper break-in, then it may cause an area on the rotor to have carbon buildup, and therefore more friction and heat buildup in that area- causing warpage.
Take this info at face value, since you are getting what you payed for it.
Brakes create heat. Duh. That's where most of the stored energy of the moving vehicles goes to when you brake. Rotors absorb, and then dissipate, most of this heat. The more effectively that a braking "system" can store and get rid of this heat, the better the braking system will operate. This mainly depends on two things : rotors and pads.
ROTORS: When braking, the rotors absorb the heat created by the friction from the pads. This heat can get the rotor very hot, over 1000 F for street cars. When this hot rotor touches a brake pad, certain materials in the pad (usually "organic" based) can melt and create gases. These gases can get between the rotor and the pad, effectively causing the pad to "hydroplane" across the surface of the rotor, causing brake fade. As the heat builds, the fade gets worse and the pad is not as effective. This is why slotted and cross drilled rotors can help prevent brake fade, by diminishing this "hydroplaning" from gases, and by letting the rotor be cooler in the first place so that the gases are not created. Then, a rotor must get rid of this heat and cool down. If you take a piece of hot metal and cool it too quickly, it will warp. Remember not to put a hot pan under cold water? Same thing. This is what can cause rotors to warp. If they are hot and they cool too quickly (from water, a puddle, too much cold air) they can warp.
PADS: Pads are a very important part of this equation, more than you may think. There are many different compounds, now with Carbon Fiber, Kevlar, Ceramic, etc. Pads create the stopping power of the vehicle. The most useful compound to us for high performance (and just Street use!) is the Carbon Fiber compounds - more on that later.
Ok, this has been simplistic. Now we look a little harder at the issues. For a brake system to be effetive, it has to generate large amounts of heat AND get rid of that heat. The rotors and pads go through this hot/cold/hot/cold cycle over and over. We can help this scenario in many different ways.
First, we can use larger rotors! The larger rotors will have more metal and surface area for braking, so they can create the same braking forces as smaller rotors, but do it while generating less heat, and have less heat to get rid of. So, the larger the rotor, the better - as long as it fits within your wheels!
Second, we can use rotors that have cooling designs, like venting or slots or cross-drilled. These rotors have more airflow, and may keep the rotor cooler in the first place, helping to prevent the heat build up and the brake fade by not allowing the rotor to get hot enough to create those gasses that cause brake fade. HOWEVER, these cooling systems are not always good. If you have a rotor that is too small for the application to begin with, and you know that it regularly gets very hot, and then it has these cooling systems, it can cool too quickly and warp itself in the process! Especially if you have cooling ducts and very open wheels. Also, these cooling systems reduce the strength of the rotor, and especially venting, reduce the overall MASS of the rotor by eliminating material. So, yes, these cooling systems can actually work against you if the rotor size is insufficient for the application in the first place.
Third, we can use different brake pads. Pads with different compounds are "optimized" to work under certain operating temperature limits, both high and low. So an organic pad may work well from 0 to 350 F, but above that it will quickly fade and melt. Or a ceramic pad may be designed to work between 1000-1500 F, strictly for race use, needing to be "warmed up". The rotors and pads commonly used in Formula 1 get around 3000F and are made from exotic compounds of Kevlar, Ceramic, etc. These are extremes, and our use is in the middle. We will rarely see use above 1000F, even in autocross events. The pads with Carbon Fiber formulas work very well because they can handle these extreme temperatures, but also have a high coefficient of friction so that they grab well under colder temperatures. This is important because for street use, you want your pads to work well when they are cold, such as in a panic stop. You don't always have time to warm them up. Also, they warm up very quickly, and their coefficient of friction actually increases as they get warmer. The classic semi-metallic pads that most cars use these days start to fade around 600-800 F, which is not commonly seen in day-to-day driving, but can easily be seen in spirited driving, or after a few high speed stops. This is when fade comes into play for these pads.
WARPAGE: The Maxima has front wheel drive, so under braking, a lot of the weight shifts forward to the front brakes. The larger a rotor, the less likely it will warp and the better it will perform. HEAT and rapid cooling is the enemy of the rotor. Let's say you do some spirited driving in the twisties and your brakes are getting hot - you can smell them. So, you should pull over and let them cool, right? WRONG! They are already very hot, and the rapid cooling could cause warping. It would actually be better to drive around a while, using the brakes periodically, and let them cool slowly. And if your rotors DO get warped? You take them in and get them turned so that they are now true again. The problem is that they will now be MORE likely to warp again, because by turning the rotors, you grind them down and take off metal which decreases their mass. Those rotors will now be more prone to warping. The more mass to the rotor, the less likely it is to warp. The nice thing about CF compound brake pads is that they wear down the rotors much slower than standard semi-metallic and organic pads (both of which usually have clay as a filler material - yuck). This alone will allow the rotors to maintain as much mass as possible through the years. Also, they work better while creating less heat, so those rotors don't get so hot in the first place. Plus, many compounds are low-dust, which we all would like. And they usually last much longer than standard SM and OR pads for not a whole lot more money. It is standard practice to turn the rotors every time you get the pads replaced, as most shops and dealerships will do. This, in time, gives you thinner and thinner rotors more prone to warping.
Also, overtightening lug nuts (as almost any shop/dealership does) can cause warping of rotors. Over time, the immense forces of the lug nuts combines with the other demands put on the rotor can cause problems. I ALWAYS redo my lugnuts after somebody else has tightened them. IT only takes a second, and they are almost always on too tight.
However, there are some things that can't be prevented. Maybe the rotors that you currently have are of a softer material or a metal that is more prone to warping. On some cars these days, the rotors are very soft and designed to be replaced as often as the brake pads.
Or if you hit that puddle with hot rotors, there is not much you can do about it. And then when you go to get them turned, they will be even more prone to warping. If your wheels are only so big, then only so much rotor will fit inside it.
Also, it is very important for carbon pads to be "bedded" properly, i.e. - broken in. It is proper for a thin, consistent layer of carbon to be transferred to the rotor. If you try to stop too hard too soon without a proper break-in, then it may cause an area on the rotor to have carbon buildup, and therefore more friction and heat buildup in that area- causing warpage.
11-30-2001, 11:04 PM
#3
wow man, VERY nice write up. i will be getting new brake pads for my 2k2 soon. one thing you didn't mention. if you go to larger rotors and larger calipers it's ALMOST useless unless you do something about the master cyclinder. if you go from 1 pot calipers to 4 pot calipers on jsut the front, that's 6 EXTRA calipers for the cyclinder to push down. you will then have much more brake pedal travel and so almsot no improvement. i would not get a upgrade without a new master cyclinder. maybe a Q45 one will fit???
12-01-2001, 08:30 AM
#5
Originally posted by got rice?
I knew all that already
You mentioned nothing of the trueness of the hubs. If the hubs are not within spec (around .003") then it will not allow the rotor to have a true mating surface.
I knew all that already
You mentioned nothing of the trueness of the hubs. If the hubs are not within spec (around .003") then it will not allow the rotor to have a true mating surface.
12-01-2001, 11:37 AM
#6
Re: All about brakes and how to prevent warped rotors. (long)
Originally posted by 2k2se6spd
The problem is that they will now be MORE likely to warp again, because by turning the rotors, you grind them down and take off metal which decreases their mass. Those rotors will now be more prone to warping.
The problem is that they will now be MORE likely to warp again, because by turning the rotors, you grind them down and take off metal which decreases their mass. Those rotors will now be more prone to warping.
Also, overtightening lug nuts (as almost any shop/dealership does) can cause warping of rotors. Over time, the immense forces of the lug nuts combines with the other demands put on the rotor can cause problems. I ALWAYS redo my lugnuts after somebody else has tightened them. IT only takes a second, and they are almost always on too tight.
. I've read enough messages here about folks who were trying to baby their breaks with the same results.Mike.
12-01-2001, 12:27 PM
#7
very nice write-up, thanks. That way I know that best pads are made of Carbon Fiber. How about rotors? What material are Nissan's factory rotors are made of? And what about the replacement rotors Nissan dealer installed on my car, are they any different in the material from those installed by the factory?
According to above, there's little written on how overtightening of the lug nuts may cause warped rotors. No car manufacturer warns about overtightening the lug nuts. Otherwise cars came with a special tool for that purpose. I have an impression that only on Maxima lugs can be overtightened.
Can the current situation be improved by using OEM rotors and Carbon Fiber pads?
According to above, there's little written on how overtightening of the lug nuts may cause warped rotors. No car manufacturer warns about overtightening the lug nuts. Otherwise cars came with a special tool for that purpose. I have an impression that only on Maxima lugs can be overtightened.
Can the current situation be improved by using OEM rotors and Carbon Fiber pads?
12-01-2001, 01:14 PM
#8
Originally posted by yo_its_ok
Steve, very close, but rotor is same size, and thicker which is a plus, but the pads, have an sensor molded in, and must be cut away.
2pistons, better, and they fit behind factory 17s. 2k2 brakes are bigger than the 2k and 2k1s,so there isn't much for you to worry about. The rotors are thicker too, yo its ok.
-Peace
Steve, very close, but rotor is same size, and thicker which is a plus, but the pads, have an sensor molded in, and must be cut away.
2pistons, better, and they fit behind factory 17s. 2k2 brakes are bigger than the 2k and 2k1s,so there isn't much for you to worry about. The rotors are thicker too, yo its ok.
-Peace
12-01-2001, 04:24 PM
#10
Senior Member
Thread Starter
Join Date: Nov 2001
Posts: 211
I'll try to answer some questions, but these are generalizations based on experience, not just specific to the Maxima.
Most rotors are made of iron because it is cheap, resists warping well (for the price) and is a good material that can take the heat and cooling process well. Again, cars are made for the masses, and the parts on them are made for "average" driving habits. However, there are different types of iron with different ratios of metals in them to create different alloys that vary in cost, hardness, and many other factors. Also, yes, the general quality of the metal comes into play as well.
The Carbon Fiber pads are not necessarily the holy grail of brake pads, but I truly believe that they can offer a vast improvement over organic pads (the cheapest) as well as the more common "semi-metallic" - for well-made, quality pads anyway. They have a lot going for them. I do not know which companies/manufacturers have models for the Maxima, but one of my favorite pads is the Carbotech Engineering Super Street "F" Compound #7266 - they are shown as available. Now, of course, what may work for one driver or one model may not work for someone else. But these pads have a wide range and are good for spirited driving and even bordering into autocross or light track time. Of course, for the best performance, you may want to try a track-specific compound.
http://www.carbotecheng.com/appguide-pads-nissan.htm
http://www.carbotecheng.com/prod-ct-compounds.htm
If I remember correctly, I heard that the front pads were semi-metallic and the rear were organic on a Maxima, but this could have been an older model or one particular car. I am not sure what the stock pads are on the Maxima. Most cars these days come with the semi-metallic pads.
When pricing CF pads, remember that they tend to last much longer, alleviate many of these problems, and let the rotors last much longer.
Most rotors are made of iron because it is cheap, resists warping well (for the price) and is a good material that can take the heat and cooling process well. Again, cars are made for the masses, and the parts on them are made for "average" driving habits. However, there are different types of iron with different ratios of metals in them to create different alloys that vary in cost, hardness, and many other factors. Also, yes, the general quality of the metal comes into play as well.
The Carbon Fiber pads are not necessarily the holy grail of brake pads, but I truly believe that they can offer a vast improvement over organic pads (the cheapest) as well as the more common "semi-metallic" - for well-made, quality pads anyway. They have a lot going for them. I do not know which companies/manufacturers have models for the Maxima, but one of my favorite pads is the Carbotech Engineering Super Street "F" Compound #7266 - they are shown as available. Now, of course, what may work for one driver or one model may not work for someone else. But these pads have a wide range and are good for spirited driving and even bordering into autocross or light track time. Of course, for the best performance, you may want to try a track-specific compound.
http://www.carbotecheng.com/appguide-pads-nissan.htm
http://www.carbotecheng.com/prod-ct-compounds.htm
If I remember correctly, I heard that the front pads were semi-metallic and the rear were organic on a Maxima, but this could have been an older model or one particular car. I am not sure what the stock pads are on the Maxima. Most cars these days come with the semi-metallic pads.
When pricing CF pads, remember that they tend to last much longer, alleviate many of these problems, and let the rotors last much longer.
12-01-2001, 04:35 PM
#11
[QUOTE]Originally posted by 2k2se6spd
[B]http://www.carbotecheng.com/appguide-pads-nissan.htm
http://www.carbotecheng.com/prod-ct-compounds.htm/QUOTE]
I couldn't find the pricing on pads. After my wtty is over, my next brake pads will be aftermarket. I don't see myself spending a whole lot on cross-drilled rotors, so will stick with OEM.
[B]http://www.carbotecheng.com/appguide-pads-nissan.htm
http://www.carbotecheng.com/prod-ct-compounds.htm/QUOTE]
I couldn't find the pricing on pads. After my wtty is over, my next brake pads will be aftermarket. I don't see myself spending a whole lot on cross-drilled rotors, so will stick with OEM.
12-01-2001, 05:39 PM
#12
Senior Member
Thread Starter
Join Date: Nov 2001
Posts: 211
Originally posted by Y2KMaxGXE-R
I don't see myself spending a whole lot on cross-drilled rotors, so will stick with OEM.
I don't see myself spending a whole lot on cross-drilled rotors, so will stick with OEM.
And that's about it.
They don't help much at all for cooling (good venting helps much more), weaken the rotor and were designed to let those gasses escape when brake pads get hot to prevent brake fade and that's it.
For extreme racing applications, every little bit helps. But if you use a decent CF pad with little or no organic binder, then you won't need (or use) the cross drilling feature of the rotors.
But, again, you won't look as cool.
For aftermarket rotors, I would look for a quality metal and THICK cheek walls with a quality curved venting system - curved vanes, not straight. This would be money better spent for performance.
But again, the little blue LED lights on the windshield washer nozzles don't make a car go faster, either, but people seem to like them.
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