Only in the case of straight vane or solid rotors if a customer prefers the appearance rotors may be. For rotors with slots machined in the same direction as the internal cooling vanes the slots should lean toward the back of the car.

Ebc Dimpled Amp Slotted Rotors Review Bmw 3 Series E90
Ebc slotted rotor direction. Checkafter having fitted the brake rotor a dial indicator. Now the problem is the internal vanes are straight so there is no indication of the direction of rotation. For rotors with slots machined in the opposite direction as the internal cooling vanes the slots should lean toward the front of the car. I have a e38 bmw 7. I understnd that if the curved slot approaches the pad like a cupped hand then the slot will actually do more to shave the pad. One main questions is what is considered a left or a right rotor.
Rotors are made from high quality grey iron to exacting standards and undergo extensive testing and rigorous quality controlslotted rotors can significantly improve brake performance and longevity when used with a matching high friction brake pad set. There is no wrong or right direction when installing your drilledslotted brake rotors. Rotor rings feature 48 directional internal curved vanes for improved rotor coolin friction rings are cast from high carbon g3500 alloy giving excellent wear properties and improved thermal capacity. All ebc disc rings are cast using the centre split casting method ensuring a balanced casting that will not distort under high heat an issue common with cheaper moulded out castings. Stoptech sportstop slotted rotors with non directional vanes or solid rotors are marked right or left so as to be consistent with rotors following rules 1 and 2. The slots are curved.
I had to replace the rotors and found a set of slotted and drilled that look good and are less expensive than oe. On non grooved ebc rotors must be removed carefully from new rotors with a suitable contact cleaner meths or white spirit to avoid contaminating pads. All ebc rotors including usr slotted rotors are british made and are precision machined in the uk. Having sold hundreds of thousands of brake. Importantthe wheel mounting flange must be cleaned before fitting the brake rotors. There are many questions when it comes to drilled and slotted brake rotors.
Slots perform their function identically regardless of direction. Bottom line dont use the slots to decide which side to mount the rotor. Rust or scale will cause runout brake judder.