The rotor on the left is a...
The rotor on the left is a zinc-plated slotted and drilled rotor. This should serve most people who want to look great and hit the track occasionally. Notice that the holes are all chamfered to help lessen the chance of cracking. For serious track time, you might be better off with the second rotor. It is a no-bling offering that can stand up to the massive stresses of heavy track time. The asymmetrical slot pattern helps provide smoother engagement through reduced harmonics. The grooves also help keep brake dust from building between the pad and the rotor face.
Rotors
Rotors are all about mass and heat dissipation. Think of the rotor as the radiator of the brake system. During braking, huge amounts of heat are generated by the action of slowing the car. This heat needs to be shed as quickly as possible to keep from cooking the brakes, which can lead to fade, or worse, failure. The more metal in a rotor, the more it takes to get them overheated. The venting design of the rotor's fins helps circulate air through the rotor and shed this heat. Also, we all see big rotors and think they look really great filling up that wheel, but there is an added benefit to large rotors. A larger rotor will have more mass for better heat control and the larger diameter will allow more leverage for the caliper. There is a point of diminishing return since as the rotor gets bigger it also gets heavier; lots of rotating mass robs acceleration and hinders stopping. Like all things in life, a happy medium needs to be kept.
Another place where there...
Another place where there are a wide array of choices is in the brake pads. For the street you need to find a pad that is a happy medium between performance and street manners....
One thing we see debated all the time is the concept of drilled rotors. Back in the day, brake pads generated quite a bit of out-gassing during heavy use, and the holes would help keep this gas from interfering with the pad-to-rotor contact. Modern pad technology has pretty much gotten rid of these gases, so why are the holes still there? The simple answer is that they look really cool. But, this bitchin' look comes at a price. If not done right, the holes are a recipe for cracking when subject to heavy use. Under hard driving, every hole can become a new place for a crack to form. If done correctly, the chance for cracks are dramatically minimized, even under hard driving conditions, but the possibility is still there. For a street car that occasionally sees open-track days, there is no problem in using a properly engineered drilled rotor. You want to make sure the rotor was designed to be drilled, was drilled correctly, and that the holes have been at least chamfered to minimize stress and wear. If you plan on hitting the track a lot and really punishing your brakes, then you will be better served to forego the holes and run a solid rotor. Besides cracking, rotors are also subject to heat-checking, which is the precursor to cracking. Heat checks are very small cracks on the surface of the rotor caused by thermal stress. While they are not a cause for concern (yet), they do indicate that the disc is not getting adequate cooling and are a warning sign that cracks may follow.
...Race pads will stop your...
...Race pads will stop your car better, but will inflict a lot of noise and dust into your daily commute. Street pads can't take the high temps of racing, but are quiet, low-dust, and operate well at lower temps. In this chart from Wilwood you can see how the various pad compounds perform as the temperature goes up...
The other most common addition to rotors is slots. Actually, they are more like grooves than slots. These don't actually weaken the rotor, and their purpose is to keep the area between the pad and rotor free of brake dust. Many competition cars will run a slotted iron rotor, and it's not a bad idea for your ride, either. The slots also lower the weight a little bit, like the holes, but it is not by much and is only a happy byproduct of the process.
Lastly, we come down to coatings. Rotors are made of iron and, as you know, iron rusts. To combat this force of mother nature, rotors are often offered with a zinc coating. The entire rotor is coated to keep it looking pretty. The area swept by the pads is also coated, but after the initial burn-in, this area is scoured clean of the zinc so the pads can work properly. If you park your car for a while, you will notice this area might start to rust, but after a couple of miles of driving all will be looking good again. If looks are more important than performance, a zinc-washed rotor is fine. However, if max performance is the goal, a zinc-washed rotor can become warped under severe usage as the coating melts and redeposits unevenly on the rotor. Pads can also become loaded up with unwanted zinc media and alter the pad's coefficient of friction.
...The pads in the top chart...
...The pads in the top chart are their various track pads, the pads on the bottom are for the street. Notice how much better the race pads work when very hot compared the street pads.
Brake Pads
Pad selection is what really determines the personality of your brakes. Nowhere else is the concept of compromise more evident than here. On the street we want quiet brakes that generate a low amount of dust. On the track we want brakes that can stop on a dime time after time without fail. Unfortunately, it is very hard to have both. The best performing pads for the track are generally noisy and generate a lot of dust. Ironically, they also have pretty poor stopping power when used at typically lower street temperatures. The best pads for the street are quiet and clean, but have a lower tolerance for high heat and are prone to fading on the track. Many people have two sets of pads for their cars: a street set for cruising and a track set for tearing it up on track day. Wilwood has a new pad called BP-10. BP-10 is used to build its "smart pads." This new compound comes closer than ever to giving the best of both worlds. It really bridges the gap by offering track performance and street manners. Still, when it comes time to seriously hit the track, it is best to go to one of its high-performance Polymatrix pads.
As they say, don't judge a...
As they say, don't judge a book by its cover. This is especially true of brake fluid, which is offered in a huge array of prices and packaging. For your average street car, the cheapo stuff on the left will do you fine and will only set you back three or four bucks. For high-performance driving, you need to step up to a fluid that is going to hold up to the punishment. It may seem tempting, but don't skimp on what you buy; it is money well spent. Many companies make performance brake fluid, and you want one that can take the heat. Also, small bottles are better since fluid, once opened and exposed to air, starts to absorb water and become less effective. Keep in mind that fluid should be changed at regular intervals--even more often if you are hitting the track.
Fluid Dynamics
The one thing these systems have in common is that they all revolve around moving brake fluid. This is the life blood of your braking system, and even the best system with the wrong or bad fluid will not get the job done. The government (DOT) sets minimum standards for how brake fluids must perform. These standards are great for a street car or mini-van, but high-performance driving means high-performance stopping, and this can overtax your run-of-the-mill brake fluid.
There are also silicone-based fluids that are less hydroscopic than ether-based fluids, but they are subject to "frothing" when forced through small orifices or subjected to high-frequency vibration. This makes them more compressible and thus less suited for high-performance or racing use.
The main difference between standard and high-performance brake fluids is how it handles heat. For example, Wilwood's EXP 600 Plus has been tested to over 626 degrees F with a wet boiling point of 417 degrees. At these temps, your average fluid would be boiling away. It also has a low moisture affinity to slow the natural absorption rate of water vapor. As brake fluid absorbs water it becomes less effective, and the temp at which it boils goes down. This is why it is important to change your brake fluid on a regular basis and only use fresh fluid from sealed containers. The true test of any brake fluid is how well it resists aeration and compressibility after it has been heated and pressure-cycled a few hundred times.
The two main enemies of brake fluid are air and water. Water in your brake fluid will lower you effective boiling point and degrade your entire system's performance. If you have air in your brake lines, this will also degrade your system since the air will compress easier than the fluid would have, thus less energy is applied to the clamping force on the rotor. This is why it is important to keep fresh, high-quality fluid in your system and make sure all air is properly bled out.
Ironically, the effect of water in brake fluid is identical to the presence of air. As the water boils and turns to a vapor it becomes compressible, just like air. The danger in bleeding your brakes and not replacing all the fluid is that it's tempting to think that fade won't be an issue since the brakes have been bled of air. Another danger area is using new brake fluid out of an opened can. Brake fluid will begin picking up water the moment the can is opened--whether it's in your car or on the shelf in your garage. Never use an old, opened can of brake fluid--you might as well keep the old fluid already in your brake system.