Editors Note:   Innovative Brake Technology by The Brake Man, Inc., has a long and distinguished history of developing leading edge technology for the automotive and racing industry. Warren Gilliland, the President and CEO, has been designing advanced brake systems since 1967, far longer than any other American aftermarket company.  Mr. Gilliland's focus and commitment to technological leadership have formed the core competencies at The Brake Man, Inc.   From the early days At Hurst/Airheart in the late 60's, and throughout the 80's at JFZ Engineered Products, the key technologies that are foundational to The Brake Man, Inc. have been the source of setting the trends for advancement of the industry.  The Brake Man is among the most knowledgeable sources of information for improving brake systems, while supplying high quality brake components, and most importantly, a reliable source of information on how to make the system produce the best results.

Over the last few years, we have seen many new developments in brake rotors for all kind of vehicles, including racecars. One of the biggest topics of discussions when gearheads get together is the relative merit of these new rotors and the advantages and disadvantages compared to those currently available. This article will look at a wide variety of the new products and give you a technical perspective to help you select wisely.

There is one thing that these new products have definitely done. That is, to confuse the consumers with their variety of claims. As with any product, in order to be a good consumer, it is important that you equip yourself with the facts relative to your purchase. In this case, you must understand what a rotor does, and what you need for your particular application. What a rotor does, and more important, does not do, are extremely important items to evaluate before you make a decision.

Since I have been designing brake systems for more than 32 years, I have had the opportunity to gain an insight to the purchasers of brake products, and how to effectively teach them about this important product. Unfortunately, in too many cases, it is evident that the purchasers of brake rotors in the high performance street and racing markets are shopping with the wrong goals in mind.

For the most part, their purchasing decisions are based around two parameters. Most often, their most important element for purchase is to compare the weight. The second most often mentioned factor is appearance. Neither of these items should ever be the primary concern in the process. In order to see why, let?s take a look at what a rotor does.

In a brake system, the master cylinder supplies pressure for the recipient, the caliper. The caliper clamps the rotor and creates force that turns energy into heat. Where does the heat go? Into the rotor.

If you think of the caliper as the faucet of your kitchen sink, and the rotor as your kitchen drain, I think you will get a better idea of how good rotor selection should work. If you are using the brake system easily on the street, or at a high banked large radius track that does not require scrubbing a great deal of speed in the corner, then your rotor will not see a great deal of thermal energy. However, if you are at a tight braking track, or on a road course where the chassis cannot be used as effectively to help the car turn, then you will be using the caliper harder, and more often, causing a greater input of thermal energy.

Naturally, because of the importance of rotating weight in racecar design, it is only natural to want to install the lightest possible rotor. If your rotor is not getting too hot and exceeding the thermal barrier of the brake pad, or boiling your brake fluid, then you are OK. For those of you who are experiencing a brake loss before the end of the race, then listen up!

Would you put a killer motor in your racecar, then put on the smallest, lightest set of exhaust pipes you could find? Would you install bigger injectors in your fuel system and then reduce the size of the fuel supply line? Well, installing an undersize brake rotor is very comparable to both of the above. It?s absolutely just as necessary to remove the heat from the brake system, as it is to remove the exhaust gasses from a motor.

How do rotors do this? Two ways. The first is volumetric displacement. That is to use their mass to absorb the energy. The larger the mass of the rotor, the lower the resultant temperature from the same input. This is the only way that a solid rotor can lower its temperature. The second way is through thermal dissipation. This is done by the ability of a vented rotor to act as a pump and move air through the center of the rotor resulting in a lower "core" temperature. A vented rotor can lower its temperature through both methods mentioned. So why all the differences in rotors?

Since the interest is high, and since the consumer market is relatively unaware of what a rotor really does, a wide variety of products are hitting the market. Some have clear advantages for limited markets, and some are outright inferior knock-offs.

Let's start with a street vehicle. Many of the rotors on passenger cars, are cast iron assemblies. Some of them are flat plates, solid or vented, which are bolted to a cast iron hub. Others are one-piece cast iron hub and rotors. Either way, they are limited in the amount of thermal energy they can absorb, because there has been no provision made to deal with large temperature changes. As the temperature increases, the rotor expands. Since the outside diameter of the rotor is free to expand and the inside of the rotor is not, (it is bolted, or permanently held to the hub), then it will relieve itself either by warping or cracking.

These rotors were not designed to deal with any more energy than would be seen on a severe street use. These rotors should never be used on racecars because the thermal energy requirements in a racecar are far more severe. The rotor designed to stop at 70 mph under street conditions will not handle multiple racing stops from 140 mph. The thermal energy is not twice as much. It is four times as much!

If you cross drill one of these vented rotors, you are creating a stress riser that will encourage the rotor to crack right through the hole. Many of the rotors available in the aftermarket are nothing more than inexpensive offshore manufactured stock replacement rotors, cross drilled to appeal to the performance market. They are not performance rotors and will have a corresponding high failure rate.

Recently, primarily due to the high failure rate, more and more of the aftermarket rotor suppliers are now slotting the rotors as opposed to cross drilling them. Slotted rotors are less likely to fail, but really do not offer any performance improvements over your factory rotors. It is important, however, that you do not confuse an aftermarket cross-drilled rotor, with a cross drilled rotor that has put the holes through the faces during the casting process. If the cross-holes were formed during the casting process, they may be less prone to failure. Since I have not personally tested any of these rotors, only time and racing reports will tell us whether they can really do the job.

Almost all racing cast iron rotors are flat plates that are mounted via an aluminum mounting "hat." This hat slides over the hub and positions the rotor where it can line up properly with the caliper. As heat is introduced into the rotor, the thermal expansion cannot damage the rotor as easily, since it is free to move on the outside diameter, and to a lesser extent, at the contact with the aluminum hat. More advanced cast iron rotors are slotted, or have other provisions to allow the hat and rotor to move freely as the temperature changes, resulting in longer lasting cast iron rotors.

Now let?s look at the special material rotors. There are rotors made from carbon and carbon composites, such as those used by Formula cars. These rotors do dissipate heat rapidly, however, the torque output of the rotor changes rapidly with temperature and is very unpredictable to the driver. There are rotors made from Titanium, some with various coatings. These rotors are extremely light and are great for certain limited applications, but are extremely expensive and do not perform particularly well dissipating thermal energy.

Cast aluminum rotors are also available. Some of them have been matrixed with other elements to improve life and wearability. Unfortunately, they have extremely limited applications because aluminum will soften considerably at temperatures easily seen in the average brake systems. Also, when cast aluminum rotors have been altered with other ingredients to improve wearability, the result could be a loss of braking efficiency. This is called "coefficient of friction." Simply put, the lower the coefficient of friction, the lower the braking torque being created. If your track is not hard on brakes, these rotors may work for you.

By far, however, the cast iron rotor is still the most popular for most racing and performance street applications. Racing cast iron rotors are mounted via an aluminum hat. This allows the rotor to expand and contract more freely than a one-piece rotor. Also, a variety of different depth hats are available for a wide range of applications. As far as the rotors, there are a variety of different manufacturer?s, designs, diameters, widths, number of veins and mounting arrangements. As far as practical application is concerned, the number of veins is a big key in determining the ability to dissipate heat. Weight is still a big factor. A lighter cast iron rotor will have thinner friction-faces and fewer veins. It will not dissipate heat as well. Your decision should be based upon the toughest track you will visit during the season. Your brake system must have the ability to remove the heat. Only the rotor can do that job.

The purpose of this rotor is to reduce the rotating mass while still maintaining its flatness. This rotor has been highly successful in replacing many heavier cast iron rotors with no loss of braking performance, yet will tolerate much more thermal energy than a cast aluminum rotor. In addition to its ability to dissipate more thermal energy, it is less expensive than its cast aluminum or titanium counterpart. Since the coefficient of friction is so similar to cast iron, the driver feels minimal difference in the performance. The success of this revolutionary steel rotor provides a wide variety of applications where they wouldn?t work before. Also, the low cost aspects of this rotor create a much larger market, especially to racers on low budgets.

Unfortunately, sometimes when a successful new product like this comes along, other companies, not fully understanding the concept or the technology used, attempt to copy. When this happens, the new product usually has a high failure rate and discourages use of even the successful new product. This has previously happened with our "Revolution"ä rotor. A cast version that has a high failure rate is now being sold. No product will fail all the time, but the failure rate is unacceptably high. This is when it is important for the consumers to beware. Do your homework before you buy. Make sure you understand whether or not the product will fulfill your requirements.

Another development has been "The Hurricane"ä rotor.

This rotor is "state of the art technology" and extremely unique. It has been patented to protect this technology. The unique interior design dissipates heat three times faster than any rotor yet tested. Manufactured from laminated steel plates, it is extremely strong, and will not shatter as cast iron under extreme use, and will result in operating temperatures at 30-40% lower than a comparable cast iron rotor. This rotor has been designed for extreme use, such as on heavy cars, or for very long races. It is on the high end of the price scale, but will work well when nothing else will. We are still developing new and unique designs that incorporate excellent cooling with long life and lighter weight. You will be seeing and hearing much more about this rotor in the near future.

Since rotors perform the function the function of removing heat, if you truly want to use the lightest rotor possible, you must pay particular attention to other factors that make your rotors work harder than necessary. For instance, if you use an inexpensive caliper, it will create much more brake drag than a high quality, stronger caliper. This is why we have created the "Tornado"ä series of calipers. A stronger, lower flex caliper creates less brake drag and increases the "cool down" time between stops. Likewise, if you use low quality brake fluid, more expansion and brake drag takes place due to the poor qualities of the fluid to resist moisture retention. These seemly insignificant items are the very reason we have a "Tech Hotline" for customers to call. No item in the system is overlooked when we set up a racecar for maximum braking performance.

The bottom line in selecting a proper brake rotor is this. Check your rotor temperatures using temperature paint. (Using a heat gun can result in errors of more than 50%). Remember that your brake pads are made to work within a certain thermal range. The rotor you choose must stay within that range or you must choose a new brake pad that will. You must also remember those cast iron rotors will begin to glow red at approximately 1200 degrees Fahrenheit. At that point, although there are brake pads that can tolerate the temperature, you are making major sacrifices in performance and wear. Choosing a larger or more efficient rotor will reduce those temperatures, increase lining life and prevent brake loss. If you are going to a gunfight, don?t show up with a knife. Although rotating weight is important, maintaining your braking ability throughout the race is more important to consistent, fast lap times.

If you would not be foolish enough to start a race with an empty gas tank to save weight, don?t start the race with an insufficient brake system. Remember, your motor takes heat and turns it into energy. Your brake system takes energy and turns it into heat. Your car must be effective at both if it is going to put you in the winner's circle.