Therefore, drilling the brake rotors may cause a very small loss of braking power, rather than an increase. If it is correct, it will point toward the back of the vehicle. 330 Front Brake Retro. Pics, Impressions, Etc. Front Drilled/ drilled and slotted rotors: Which way do slotted brake rotors go . Slotted rotors typically have four to eight evenly spaced shallow grooves milled into both surfaces of the rotor. These slots, or grooves, do not go the whole way through the rotor, so they do not affect the structural integrity like drilling does. On most vehicles, the factory brake rotors are usually straight vane rotors. For drilled and slotted rotors, it is important to pay attention to which is the left and right rotor. 2018 porsche 911 gt3 drilled brake rotors | porsche. Luckily, if your rotors are not labeled, there is an easy way to tell. Given the choice between drill holes and slots, the drill holes will give you better braking power over slots for normal cit...