Eighty percent of the brake rotors sold in this country are made outside the United States. A lot of the companies making these rotors are only concerned about fit. They believe that if the rotor fits on your car then it's a good rotor. The actual performance of the rotor is secondary. They all know that a lot of car owners always shop for the lowest price.
This brake rotor thing has gotten so bad that rotor companies are starting to sue each other. The Bingham Farms-based Affinia Group Inc. and its subsidiary Brake Parts Inc. recently filed suit in U.S. District Court in Richmond, Virginia, claiming Dura International is falsely advertising its brake rotors as meeting the specifications of automakers. Dura responded by stating, "No government standards exist specifically for rotors. Each and every manufacturer is independently responsible for producing quality product meeting acceptable standards in fit, form, and function." This one will be in court for years.Eric Bolton, a spokesman for the National Highway Traffic Safety Administration, said the agency is aware of the controversy and is monitoring complaints and field data through its Early Warning System.
Even Raybestos has jumped in. It's running ads that show the difference between its rotor and the rotors produced by the competition. Basically what you have to remember is that just because a brake rotor fits your car doesn't mean that it's the equivalent of the original rotor. There can be significant differences in quality.
Some of the cheap brake rotors are much thinner than name-brand aftermarket and original equipment rotors. These cheap rotors are being sold to unsuspecting consumers as standard replacement rotors. They simply can't absorb the heat that's generated from aggressive braking forces.
Cheap rotors are made from damped steel. You can test them by hitting them with a hammer and listening for a ringing sound. You might have to tap on a few rotors to hear the difference, but once you hear it, you'll know what I mean. It's sort of like tapping on a forged crankshaft and a cast crankshaft. Try tapping on several brake rotors as a test.
Some of you don't actually get involved in the purchase. You outsource the task to your local shop. Most people have never given much thought to the quality of the brake rotors on their cars. I can almost guarantee you probably spent more time thinking about the price than you did about the quality. That's not a good situation.
What Does a Brake Rotor Do?
The basic scientific principle here is that friction between the pads and the rotor converts mechanical energy into heat energy. Just how much heat depends on vehicle speed, vehicle weight, and how hard the brakes are applied. For example, when I'm at Sebring my brake rotors normally reach about 1,200 degrees F.
Slotted or Drilled?
Drilled brake rotors became a huge fad a few decades ago. Today drilled rotors are generally considered a cosmetic item. They gained favor because of the belief that they prevented outgassing. Outgassing occurs at extreme temperatures when the bonding agents that hold the pad material together break down into a gas. This gas creates a pneumatic barrier between the rotor and the pad, reducing the amount of friction between them. Cross drilling, or slotting, creates a path for the outgassing that occurs during extreme braking conditions. These conditions are seldom reached on the street.
But rotors can crack under very intense heat. I cracked even my rear rotors before I gave up on drilled rotors. Basically you don't need drilled rotors on the street, and they don't work very well at the track. Got the idea here?
Two-Piece Brake Rotors
There are two main reasons for choosing a two-piece rotor over a standard one-piece. The first is weight savings. A two-piece brake rotor's center aluminum hat reduces the overall weight by an average of 3 pounds versus a one-piece, cast-iron rotor.
Remember how I said earlier that lightweight rotors are generally cheap junk? Well, with a two-piece rotor you can have light weight and strength at the same time. The actual rotor can be substantial enough to dissipate heat properly, while the aluminum hat section saves weight. This is the best of both worlds.
The other big advantage of the two-piece rotor is that it's easier to vent air through the rotor's center. The ideal brake duct is one that pushes air into the center of the brake rotor, thus allowing the heated air to exit through the vanes. Two-piece rotors are ideal for this ducting and cooling.Two-piece rotors can be very expensive when you first install them. A one-piece brake rotor is cheaper, but not by a lot. I might add that I've never cracked a Wilwood brake rotor, but then again I've never cracked a NAPA premium rotor. I have, though, broken just about everything else.
A lot people also prefer two-piece rotors for cosmetic reasons. The black aluminum center hat bolted to the rotor ring gives the brakes an aggressive, race look. Just be prepared to pay the price.