Though not perfect, but these requirements are met by cast iron. However, the pair take a few limits widespread iron brake discs. Chief of them is the fact that the cast iron during heating is much more exposed to corrosion, so it can not be used on sports cars. The alternative is a disc of stainless steel. They are much more resistant to corrosion, but their frictional properties is not as good as cast iron. The lack of increase in diameter up for these items. discs perfectly transfer heat to 400 degrees, and it does not harm the ingress of moisture.
However, all metal disks have a common negative quality, namely, weight. Too much rotating mass adversely affected by driving characteristics. The solution was found in the carbon discs. They made of carbon fiber and also low weight, have a number of advantages. This improved frictional properties, and absolute corrosion resistance, and greater resistance to high temperatures. However, they There is one drawback, which virtually eliminates the possibility of their use in conventional engines.
Carbon wheels cope well with their responsibilities, just being heated up to 200oC. Therefore, their application limited to a sports car, where they were simply irreplaceable. It is also worth noting that the price of carbon disks are significantly higher than the cost of iron or steel. There are also ceramic discs that are in all parameters exceed the carbon and the more iron. They can withstand temperatures up to 1000oS, but the high cost makes it possible to install them only on luxury cars. The characteristics of the brake discs are not determined only material. With active driving with frequent stops discs and pads are heated red hot. At the same time begin to evaporate binders that make the gas layer between the disc and pads. This leads to reduce friction and a significant deterioration of control. This problem is solved very easily by punching the brake discs. The essence of this process is to drill a few holes in the details. Through them, by heat transfer and flow of unwanted gas. But the process of drilling is not so simple. Must be very accurately calculate the location and diameter of the holes, otherwise the disc may break even at the first visit. Perforating discs can be trusted only to professionals, but better to buy directly and completely ready. A little later, after the perforated discs a disc with the grooves, which at first were considered improved version of the diversion of gas. However, experience shows that with time the depth of the grooves decreased, therefore reducing heat transfer and is not performing its functions under the outflow of gases. For obvious reasons, this technology is not widespread. Disc braking systems continue to evolve and to this day. Until recently they were applied only to passenger cars. Trucks and buses to trust only the drum system. Now, thanks to constant improvements, the disk system is gradually being introduced in heavy vehicles. Disks are more reliable, durable, effective. But do not forget that no matter what may seem the ideal braking system, a crucial role still played by the human factor. Also do not forget that any disk eventually wear out and need time to replace it with a new one.