Pros and Cons of Cross-Drilled and Slotted Rotors
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A recent trend in the sports car market is the use of cross-drilled or slotted rotors. You see them on all kinds of cars today, and while they may look nice, few people know the benefits to using them. Many people don't even know what the slotted rotors are for. Are they just for looks, or do they actually increase your braking performance in some way? There are pros and cons to using them, and that's what we'll be focusing on here.
Slotted rotors are generally more reliable than their cross-drilled counterparts. One of the biggest benefits to using a slotted rotor is that the slots help pull brake dust away from the pads. By reducing the debris between your pads and rotors, you allow more of the pad's surface area to come in contact with the rotor, which means better grip, and better stops. The coefficient of friction is increased, so you're using less energy every time you step on the brakes. In other words: you can stop your vehicle faster with the same effort. This is why motorsports such as NASCAR advocate the use of slotted rotors on their race cars.
However, there is a tradeoff that occurs to gain this extra stopping power. By cutting into the brake rotor—whether slotting or cross-drilling—you are effectively reducing its structural integrity. So even though this reduced unsprung weight (an issue near and dear to racers everywhere) it's also putting your brakes under stress. To some, however, that extra stress is worth the extra stopping power.
Cross-drilling rotors was common in the old days of asbestos brake pads—think 1950's technology here. When these pads were applied, gases were released that would get trapped between the pad and the rotor. This was referred to as "gassing out" or "outgassing" When that happened, the friction between them would decrease, meaning the brakes were less effective. To counteract this, holes were cross-drilled into the rotors to give the gas somewhere else to go, and while this may have been effective fifty or sixty years ago, today we live in a world of carbon ceramic brake pads, and they don't experience this same phenomenon. In today's cars, if you use cross-drilled rotors under heavy load, such as on the race track, you're losing structural integrity even more than with a slotted rotor, which makes your rotors much more prone to cracking.
To their credit though, cross-drilled rotors are considered visually appealing in many situations. When run on cars that won't see the track, you can run cross-drilled rotors and not have to worry about the cracking mentioned above, because on the street your vehicle won't generate enough heat to crack them. In other words, your choice of brake pads is purely aesthetic and all about personal preference, until you decide to hit the track and push your car to its limits.
