Join Date: May 2004
Location: Behind the steering wheel
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Brembo currently operates in 3 continents with production plants in 10 countries; our commercial sites are based also in Sweden, France, and USA, while we sell our products in 70 Countries in the world.
At present, Brembo employees over 5300 people, nearly 10% of which are engineers and product specialists working in research and development.
Anybody who works on brakes knows what brake rotors do. They provide a friction surface for the disc brake pads to rub against when the brakes are applied. The friction created by the pads rubbing against the rotor generates heat and brings the vehicle to a stop.
The underlying scientific principle here is that friction converts motion into heat, a LOT of heat! The amount of heat that is generated depends on the speed and weight of the vehicle, and how hard the brakes are applied.
A large, heavy vehicle, like a Chevy Suburban, will obviously generate more heat when braking than a Toyota Echo if both vehicles brake from the same speed. But the little Toyota may produce more heat than the big Suburban if the braking speeds are different, say 60 mph for the Toyota and 20 mph for the Suburban. Speed multiplies the effect of weight and creates momentum (also called "inertia" or "kinetic energy").
The metallurgical properties of a rotor determines its strength, noise, wear and braking characteristics. The casting process must be carefully controlled to produce a high quality rotor. You cannot just dump molten iron into a mold and hope for the best. The rate at which the iron cools in the mold must be closely monitored to achieve the correct tensile strength, hardness and microstructure.
When iron cools, the carbon atoms that are mixed in with it form small flakes of graphite which help dampen and quiet noise. If the iron cools too quickly, the particles of graphite do not have as much time to form and are much smaller in size, which makes for a noisy rotor.
The rate of cooling also affects the hardness of a rotor. If a rotor is too hard, it will increase pad wear and noise. Hard rotors are also more likely to crack from thermal stress. If a rotor is too soft, it will wear too quickly and may wear unevenly increasing the risk of pedal pulsation and runout problems.
The composition of the iron must also be closely controlled during the casting process to keep out impurities that may form "inclusions" and hard spots. One rotor manufacturer says they sample the molten iron every 15 seconds to make sure the composition is correct. The molten metal is also poured through ceramic filters that trap contaminants. Even the sand that is used to make the molds is specially treated to control moisture content. This helps keep the sand in place and prevents core shifts that can affect porosity, dimensional accuracy and balance.
The grade of cast iron that is used in a rotor may even be changed to suit a particular application. One aftermarket rotor manufacturer uses a special grade of "dampened iron" to make replacement rotors for 1997-2002 Chevrolet Malibu and its sister vehicles (Olds Alero, Olds Cutlass and Pontiac Grand Am). In this case, the original OEM rotors turned out to be too noisy so General Motors switched to a dampened grade of iron to cure the problem.
Vehicle manufacturers use a wide variety of different cooling rib configurations in their rotors. They do this to optimize cooling for different vehicle applications. So even though the brakes may appear to be identical on two different models, one may require increased cooling because the vehicle is heavier, has a more powerful engine, has less airflow around the brakes, etc.
Some aftermarket rotor manufacturers use the same rib design and configuration as the OEM rotors, while others do not. Some change the rib design to simplify the casting process or to reduce the number of different rotor SKUs in their product lines.
The OEMs currently use almost 70 different rib configurations in their rotors. Some ribs are straight, some are curved and some are even segmented. Some rotors are directional and some are not. Some rotors have evenly spaced ribs while others do not. Some ribs radiate outward from the center and others go every which way.
One reason why they use so many different rib patterns is to maximize cooling and to reduce harmonics that contribute to brake squeal. Changing the rib design changes the airflow, cooling and noise characteristics of the rotor, which may make things better or worse depending on the application. That is why some aftermarket rotor manufacturers use the same basic design as the original, while others stick with more traditional venting.
One brake manufacturer showed us a cutaway of an offshore "economy" rotor for a particular vehicle that had 32 ribs. The OEM rotor, by comparison, had 37 ribs and provided up to eight percent better cooling than the economy rotor when tested in the laboratory. And because the OEM rib design ran cooler, pad life was 28 percent longer than the economy rotor.
Another aftermarket brake manufacturer showed us test results that proved their rib design improves cooling and makes their rotor three times quieter than a competitive rotor. The recorded sound levels showed noise as high as 85 decibels screaming out of the Brand X economy rotor compared to only 40 to 50 decibels from their own "premium" quality rotor.
|There is a common fallacy out there that increasing your brake pad size in terms of swept area will increase the stopping power of your car through greater friction. From a standpoint ignoring operating temperatures this is in fact false. The force of friction is determined by physics as the force down on the object times the coefficient of friction. As such there is no surface area in the friction equation. However, the temperature of the pad varies throughout its use changing the coefficient of friction at each point along its temperature slope in a non-linear/non-progressive manner. As such it is possible that a larger pad will change the friction force favorably given pad makeup. It certainly will change the amount of time before the brakes enter the proper range and when they leave the range. It will also influence when and how long it is at the peak performance point. Meanwhile, modifying the pad material can change this operating range. As such the affect of increase in pad size on braking friction would depend on the makeup of the pad. Also note that the only way to modify the force down is to change the brake piston force (by size changes or number for example).|
|This does not mean that a larger brake pad does not help braking! The benefit of a large brake pad comes into effect when you consider thermal dissipation. The larger the pad the more this thermal temperature (created by the interaction between the pad and rotor) is spread amongst a pad. This means less temperature is concentrated at one point on the pad and the rotor absorbs more heat. This decreases the likelihood that the pad itself will heat beyond operating temperature. If the pad were to go beyond operating temperature it would glaze over resulting in brake fade. Furthermore, a larger pad results in a longer service life of the pad since there is more pad material to consume.|
|The second thing you can do to improve your brake performance is often to go to a larger rotor. We all know that this gives the rotor further ability to dissipate heat away from the pads through itself and through the air (conductive and convective heat transfer). So obviously a larger pad, a larger rotor, or both result in better brake performance by avoiding brake fade.|
|Cross Drilled Rotors have been considered by many professional race car drivers as a miracle product. Cross Drilled is the process by which Drilled holes are placed into unique areas of the Rotor which ultimately improves the quality of your brakes. When driving, stock Rotors can heat up to a very high degree and cause a failure to the brakes and to the Rotor itself. With the Cross Drilled design, your Rotors overpower the heat and keep the brakes in a newer and more reliable condition. Statistically through testing and research, these top quality Brakes have been established a 70% increase (opposed to stock Rotors) in intensive braking safety performance. This High Performance style has saved the lives of many drivers and brought contentment to many car-enthusiasts worldwide.|
Slotted Rotors are the ultimate advantage to the concrete construction of Brake Rotors. Many Stock Rotors have a history and a tendency of cracking, bending, or just wearing out too quickly. With the Slotted option, the tendency of the Rotor has been known to endure a lifetime TWICE the amount of a Stock Brake Rotor. The Slotted design keeps the Rotors cool from the overheating gases and the excessive use of brakes. Not only has this option improved the performance of the Rotors but they have also improved the gripping functioning of the brakes when being pressed down on the Rotors. The flat OEM (Stock) surface of the Rotors makes it difficult for the brake pads to grasp on properly as opposed to the gripping of the Slotted Rotors which helps the brakes give the car a smoother and less enduring stop. Statistically, according to research and testing, the Slotted Design has a 40% more efficient and safer braking distance than stock Rotors.
Slotted rotors, have engraved indented lines in the brake rotors. When you brake, the Brembo brake rotors grip on to the brake pad much better. Regular rotors have a smooth surface, while breaking it does not allow the pad to grip onto anything resulting in less braking performance. Slotted rotors improve the braking distance by 40% then a regular OEM (Original Equipment Manufactures) rotor.
|For maximum braking performance it is recommended to get both cross drilled rotors and slotted. If you plan to race the car at tracks, we would recommend you to get only slotted rotors since too much racing and extreme braking may result in the rotor building too much heat and cracking. It will only result under extreme conditions. If don't drive recklessly and only race once in a while it will not affect you. It will only affect you if you race on the track at 130 MPH quarter mile and do 3 - 5 runs.|
|So what do ventilated rotors accomplish? Well, the concept is that they will help cool the rotors. We discussed earlier that giving up mass for surface area to gain cooling of the rotors should only be done when optimal. Vanes are the optimal method of achieving these goals. The rotors are designed to increase surface area and to flow air in the middle of the rotors. The increased surface area to the air clearly provides for more cooling from the air at the cost of mass. So why does this method work while the others fail? The first reason is that a ventilated design flows a lot of air through a rotor. A ventilated rotor acts as a centrifugal pump sucking air into the rotors. This is why rotors with curved vanes provide better braking.|
|Okay, so Dogzilla and I were discussing rotors and what not when I posed a question. Where do rotors really come from?|
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