The Care and Feeding of Your Brake Rotors
Eighty per cent of the brake rotors sold in this country are made outside the United States. A lot of the people making these brake rotors are only concerned about fit. If the rotor fits on the car then it’s a good rotor. The actual performance of the rotor is secondary.
The brake rotor thing has gotten so bad that brake 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, Va., 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 could 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 running ads that show the difference between their rotor and the rotors produced by the competition. Basically you have to remember that just because a brake rotor fits your Corvette doesn’t mean that it’s the equivalent of the original rotor. There are some significant differences in quality.
Some of the cheap brake rotors are much thinner than name-brand aftermarket and original equipment brake rotors. These lightweight (cheap) rotors are being sold in to unsuspecting consumers as standard replacement rotors. They simply can’t absorb the heat that’s generated from aggressive braking forces.
Increasing the air gap between the rotor faces often reduces the thickness of the discs in these “lightweight” rotors. This saves about 4 to 5 lbs. of cast iron per rotor, and reduces the manufacturing cost $3 to $4 per rotor. Unfortunately, this trick also reduces brake rotor strength, the rotor’s ability to absorb and dissipate heat, and the ability to resurface the rotor safely the next time the pads need to be replaced. None of these things are good.
Cheap rotors are made from damped steel. You can test then 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’m talking about. It’s sort like tapping on a forged crankshaft and a cast crankshaft. Keep in mind that original Corvette rotors are made from better steel than the brake rotors on your S-10 pickup. That may not be the case with offshore brake rotors. 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. If you’re normal you’ve never given much thought to the quality of the brake rotors on your car. I can almost guarantee you spent more time thinking about the price than you did about the quality. Not Good
What Does a Brake Rotor Really Do?
Brake rotors provide a friction surface for the brake pads to rub against when the brakes are applied. The friction created by the pads rubbing against the rotor generates heat and brings the vehicle to a stop.
The basic scientific principle here is that friction between the brake pads and the brake rotor converts mechanical energy into heat energy. Just how much heat depends on the speed, the weight of the vehicle, and how hard the brakes are applied. Just to give you an example when I’m at Sebring my brake rotors normally reach about 1200 degrees. That’s a lot of heat.
The brake system on your Corvette must be capable of absorbing a lot more mechanical energy (horsepower) than your engine produces. Remember the heat energy that’s generated under braking happens over a very short period of time. Sixty to zero happens a lot more
quickly than zero to sixty. Corvettes can stop faster than they can accelerate. That means the brake system has to shed horsepower very quickly.
This intensity actually multiplies the amount of horsepower that must be absorbed. It can be as much as six times depending on the stopping distance. A rapid stop from 60 mph might require the brakes to absorb the equivalent of up to 600 horsepower. I don’t even want to do the calculations for turn 17 at Sebring where I’m entering the corner at around 130 miles an hour.
Slotted or Drilled?
Drilled brake rotors became a huge fad a few decades ago. Today drilled brake 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. This gas barrier reduces the amount of friction between the rotor and the brake pad. Cross drilling or slotting creates a path for the outgassing that occurs during extreme braking conditions. These conditions are seldom reached on the street.
Baer Racing says while cross-drilled or slotted rotors produce a strong visual appeal behind a modern open wheel they have only a very slight performance edge when pad outgassing occurs. In other words the holes don’t do much.
What does happen it that they crack under very intense heat. I even cracked my rear rotors before I gave up on drilled rotors. Bascially you don’t need drilled brake rotors on the street and they don’t work very well at the track. Got the idea here?
The best explanation of why you don’t need drilled brake rotors is found in the advertising for Brembo. Brembo states “Brembo Sport drilled brake rotors provide excellent stopping power in everyday traffic, as well as more spirited, high performance street and highway driving.” They then go on to point out that “Brembo Sport slotted brake rotors provide excellent stopping power in everyday traffic, as well as high performance street and track driving.” Notice that there was no mention of using drilled brake rotors for track use? Now are you getting the point?
