There are generally two forms of a brake rotor or brake disc – solid and/or vented or ventilated brake rotors. Solid brake rotors, as the name implies, is one solid disc. Vented brake rotors are two discs conjoined at the middle by vanes or lined structures. The purpose of vanes is to provide more cooling and heat dissipation of the brakes.
Normally, only front brakes on cars are equipped with vented brake rotors. The reason is because the majority of the work performed to stop your vehicle from motion is done by the front brakes. Front brakes are more likely to overheat during heavy brake applications, which is why vented, front rotors are important. Rear brakes are usually made of drums or solid discs because this is an adequate configuration for the rear brakes. Not to mention--it is more cost effective. This isn’t to say that rear, vented brake rotors do not exist or that people do not use them--there are sports cars and more top end vehicles that have front and rear vented disc brakes. Source: dcperformance.co.uk
When it comes to vented disc brakes, there are a few different designs to mention.
Rotor Vane Types
There are different types of brake rotor vane designs depending on the application of the vehicle. Some vane designs may be more effective than others, but they all help to serve one purpose – to provide even better cooling and braking performance.
Straight, Radial or Non-Curved Rotor Vanes – this type of vane design in a brake rotor is the most popular and widely used for general brake applications, such as every day, street driving. These brake rotors are light in weight because they require less material (compared to curved rotors), but have better cooling capabilities compared to solid rotors. When compared to other rotor vane designs however, there are other designs that have better cooling and performance capability. Other straight-vane designs include:
- The Pillar Vane – this vane design uses a patterned arrangement of “dots” or lines for the vanes, casted between the two friction plates.
- The Variable Vane – this vane design is similar to the straight vane but comes with a variation in vane pattern and a less predictable pattern of arrangement.
All of the designs mentioned above are “non-directional,” meaning these designs are not side specific. A pair of drilled and slotted, straight vane rotors can be installed on the right or left side of a vehicle—performance is not very much affected by the direction of the slots/cross drills. People often confuse “directional” and “non-directional” with the drill pattern of the rotors, but these terms are meant primarily for the vane structure. With this being said, brake rotors are typically directional and side specific when the vanes are curved.
Curved Rotor Vanes – this type of rotor vane is predominantly used for motorsport or racing applications and is most commonly used by race car professionals. These rotors are typically heavier than straight vane rotors because more material is used for the curved vanes. Since there is more material, curved vanes have better thermal capacity and are able to withstand heavy brake applications better. Some other curved vane designs are the variable curved vane or convergent vane rotors.
All brake rotor manufacturers have their opinion about what is best for performance and how brake rotors should be installed. Our advice is that vane direction is more important when it comes to performance compared to drill pattern direction. Source: socalevo.net
NOTE: Some car manufacturers have left and right side specific rotors with the vane direction going opposite directions when installed, others have them going the same direction. For street applications, it may not make much of a difference. We recommend that you install rotors and follow the directions of the manufacturer.