Brakes = Part II
12-03-2000, 02:20 AM
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Here is some more on drilled vs. slotted
The Brake Zone
CROSS DRILLED, SLOTTED, VENTED ROTORS
While there are many rumors and home made theories about the benefits of different rotors, lets try to dispel them and deliver some facts. Cross drilled rotors have long been the subject of ridicule and blame. For years so called racers have been blaming poor old cross drilled rotors for failures that were not directly related to them. Cross drilled rotors were designed with the intent that cool air would pass through the rotor to help reduce the heat deflection through the rotor. An interesting fact about (all)"vented" rotors is that they pull air from the center of the rotors and allow it to pass in an outward direction. By cross drilling the rotors, you can achieve more cool swept area of the rotor
and pad while sweeping the pad and rotor surface at the same time. This is very beneficial for performance and daily driving. The cross drilling also makes the rotor surface more aggressive to give a better initial bite under heavy
breaking. Many wanna be "Racers" believe that all cross drilled rotors are prone to cracking. One of the things that they don't understand is that all rotors are prone to crack given wrong or extreme conditions. The difference is the heat threshold that each of these rotors will allow.
A slotted rotor will have a higher thermal thresh hold but can still fail. One of the most overlooked reasons for brake failure is mismatched pads and rotor combination. With out the correct combination, your performance level could really be at risk as well as your safety.
Just because a rotor is cross drilled does not mean that it is at risk to fail or crack. Many manufacture's use different methods to help prevent rotor failure. One such method is to radial chamfer each gun drilled hole in the rotor surface. This as you may recall from physics class makes the edge stronger. (a curved surface is stronger than a flat one). By doing this you also make the rotor more aggressive with out making them more abusive toward the pads. This also allows for more air surface for cooling.
Slotting the rotors is generally intended to pick up where cross drilled rotors leave off. They tend to have a higher thresh hold to heat there for enabling the brakes to function at much higher temperatures. By slotting the rotors you create "sweep" for the pads. At high temps cross drilling becomes non effective. Rotors can't pull air through after extreme temps. The rotor actually becomes a heat sink. As the cross drills become non effective, the slots can sweep the gas pocket out. For a real world example, look at "real race" cars. Mainly, road race cars such as Trans Am, IMSA, and CART will exclusively run slotted rotors with very aggressive pads. While many teams have their particular love of brand, they all have the same basic function. One must also realize that when operating a performance system, there will be a trade off in the system some where. Generally performance street systems are designed to compromise the pads life with added braking ability. By doing this, one can expect certain "better" braking while not sacrificing the life of the rotor.
As you move up in pad compound, you must realize that it takes more heat to get these brakes working at optimum standards. The trade off here is accelerated rotor wear.(Here's were combination playing can pay off / or not).
Ideally, you would want to run a new pad on a used rotor and vise versa when seating new components. Depending on the track conditions and characteristics of the particular car, bypass stagger (brake ballast) in conjunction with pad and
rotor combo can be the deciding factor in longevity and performance.
For most import and domestic applications, there should be little more than a need for basic cross drilled or slotted rotors with carbon based pads and steel braided lines. Not all big brake kits are practical for each application. They
may not even be available for your car or truck. The last important factor is to take into consideration is driver charctoristic's. Late braker's will generate more heat cycles than a "two footed" driver. The dreaded "two foot" driver will just eat brakes period.
Copyright – Avalon Ent – Racing Division – All Rights Reserved
The Brake Zone
CROSS DRILLED, SLOTTED, VENTED ROTORS
While there are many rumors and home made theories about the benefits of different rotors, lets try to dispel them and deliver some facts. Cross drilled rotors have long been the subject of ridicule and blame. For years so called racers have been blaming poor old cross drilled rotors for failures that were not directly related to them. Cross drilled rotors were designed with the intent that cool air would pass through the rotor to help reduce the heat deflection through the rotor. An interesting fact about (all)"vented" rotors is that they pull air from the center of the rotors and allow it to pass in an outward direction. By cross drilling the rotors, you can achieve more cool swept area of the rotor
and pad while sweeping the pad and rotor surface at the same time. This is very beneficial for performance and daily driving. The cross drilling also makes the rotor surface more aggressive to give a better initial bite under heavy
breaking. Many wanna be "Racers" believe that all cross drilled rotors are prone to cracking. One of the things that they don't understand is that all rotors are prone to crack given wrong or extreme conditions. The difference is the heat threshold that each of these rotors will allow.
A slotted rotor will have a higher thermal thresh hold but can still fail. One of the most overlooked reasons for brake failure is mismatched pads and rotor combination. With out the correct combination, your performance level could really be at risk as well as your safety.
Just because a rotor is cross drilled does not mean that it is at risk to fail or crack. Many manufacture's use different methods to help prevent rotor failure. One such method is to radial chamfer each gun drilled hole in the rotor surface. This as you may recall from physics class makes the edge stronger. (a curved surface is stronger than a flat one). By doing this you also make the rotor more aggressive with out making them more abusive toward the pads. This also allows for more air surface for cooling.
Slotting the rotors is generally intended to pick up where cross drilled rotors leave off. They tend to have a higher thresh hold to heat there for enabling the brakes to function at much higher temperatures. By slotting the rotors you create "sweep" for the pads. At high temps cross drilling becomes non effective. Rotors can't pull air through after extreme temps. The rotor actually becomes a heat sink. As the cross drills become non effective, the slots can sweep the gas pocket out. For a real world example, look at "real race" cars. Mainly, road race cars such as Trans Am, IMSA, and CART will exclusively run slotted rotors with very aggressive pads. While many teams have their particular love of brand, they all have the same basic function. One must also realize that when operating a performance system, there will be a trade off in the system some where. Generally performance street systems are designed to compromise the pads life with added braking ability. By doing this, one can expect certain "better" braking while not sacrificing the life of the rotor.
As you move up in pad compound, you must realize that it takes more heat to get these brakes working at optimum standards. The trade off here is accelerated rotor wear.(Here's were combination playing can pay off / or not).
Ideally, you would want to run a new pad on a used rotor and vise versa when seating new components. Depending on the track conditions and characteristics of the particular car, bypass stagger (brake ballast) in conjunction with pad and
rotor combo can be the deciding factor in longevity and performance.
For most import and domestic applications, there should be little more than a need for basic cross drilled or slotted rotors with carbon based pads and steel braided lines. Not all big brake kits are practical for each application. They
may not even be available for your car or truck. The last important factor is to take into consideration is driver charctoristic's. Late braker's will generate more heat cycles than a "two footed" driver. The dreaded "two foot" driver will just eat brakes period.
Copyright – Avalon Ent – Racing Division – All Rights Reserved
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