The majority of us are constantly trying to find ways to improve the performance of our Corvettes. More horsepower means faster acceleration, and most of us would do anything to get it. As our cars get quicker and reach higher speeds, we suddenly realize our factory brake systems are inadequate. Warped rotors, brake fade, and the smell of burned brake pads are a good indication you're putting an increased load on the factory brake system. If that's the case, there are several steps you can take to slow down your Corvette.
What Is The Matrix?One of the first things you can do to upgrade your Corvette's brakes is move to a pad with a higher-friction compound. Older models that still use drum brakes in the front and rear can benefit from a shoe that's manufactured with a higher-friction matrix. Some manufacturers use Kevlar within the shoe matrix, along with other high-grade fill materials to create a shoe that can stop the vehicle more quickly, while effectively dissipating heat.
Late-model Corvettes often use state-of-the-art pads with a complex pad matrix that include a carbon semi-metallic compound that can stop the vehicle with ease. What makes up a performance pad? Surprisingly, most of the pad matrix is made from binders and fillers. Although most brake-pad manufacturers will not disclose the particular compound formula, many use common ingredients such as talc, silica graphite, shredded rubber, and even crushed walnut shells as filler material. Semi-metallic compounds often use steel, copper, or brass, mainly to improve thermal conductivity. The mixture of the pad matrix and how much of one component is added more than another will affect the overall friction abilities of the pad. For example, many OEM applications use a carbon-metallic compound that has a layer of carbon over the rotor to achieve a higher coefficient of friction between the metal and pad. This is usually the black soot you're constantly wiping off your wheels.
It would seem everyone would want a set of pads that allow their cars to stop quicker than stock, but a problem can arise if the front pads have significantly more friction than the rear pads or drums. Upsetting the front-to-rear brake balance of the vehicle can lead to poor braking and may affect the performance of the ABS system on late-model Corvettes. Although there are aftermarket higher-friction pads available, there's a potential side effect with these pads: overheating the factory rotor. This can lead to severe warping and stress fractures on a stock rotor, and to its demise more quickly than with the factory pads.
If you're attempting to upgrade your pads, ask the manufacturer if they work well with the factory rotors. Many tests on a simple pad upgrade average 5 to 10 percent improved stopping distances over stock, especially on earlier models with a front-disc and rear-drum setup.
Heavy MetalAs friction and heat increase, the rotor becomes the weakest link. Factory cast-iron rotors are porous and can retain heat in the microscopic pockets within the metal. Using a higher-friction pad could quickly warp or cause stress cracks on a factory rotor, which can be improved by cryogenically freezing the rotors. This process slowly lowers the temperature of the metal to minus 30 degrees F. The freezing process forces the metal molecules closer together, which makes the metal harder and allows it to dissipate heat more quickly. This is a great way to use a higher-friction pad on a stock rotor. The average cost of cryogenically treating a rotor is $40-$50 a pair.
Some aftermarket rotors are available cryogenically treated, but most simply add higher nickel content, 20 percent in most cases, to the metal alloy to strengthen the rotor. A stronger rotor makes it safer to use higher-friction matrix pads, without the threat of heat-induced cracks or warping. Aside from making the rotor stronger, many aftermarket manufacturers increase the diameter size. A larger-diameter rotor means a larger surface area for the pad to work with, greatly increasing braking potential. Upgrades such as these don't necessarily add more stopping power to your Corvette, but they do increase pad and rotor life, as well as dramatically increase the consistency of your Corvette's stopping potential, which is just as important.
A Hole In The TheoryMost aftermarket rotors are also cross-drilled or slotted to improve performance. However, many cross-drilled rotors can develop stress fractures, and removing material from the rotor takes away from its overall surface area. This is one of the reasons many aftermarket brake manufacturers prefer to use larger-diameter rotors to compensate. Nevertheless, consumers still like the look of cross-drilling, and rotor manufacturers are swayed by what Corvette owners want on their vehicles.
The truth is, however, that after countless hours of testing in the lab and on the track, many brake experts prefer to use a rotor featuring a slot that's angled at 45 degrees to the rotor's center. This pitch effectively swipes and expels debris from the pad and ensures a fresh layer of brake-pad compound is always in contact with the rotor's surface. Another misconception is how the angle of the slot faces. The correct way to mount a slotted rotor is so the direction of the angle (from the rotor's edge to the center of the hub) points in toward the vehicle. In other words, it should look like a "greater than" sign (>) where it opens out toward the front of the vehicle. This also means the right- and left-side rotors must be machined differently. The effect of this modification will not make your Corvette stop better, but it will increase its consistency of stopping, eliminating any fade, and lengthen rotor and pad life.
Getting A GripIf upgrading to an improved set of rotors and pads still doesn't have you stopping on a dime, upgrading to a better set of calipers is the next step. Given that late-model Corvettes already have a great set of four-piston calipers, earlier models didn't benefit from this as much. Many had problems with corrosion on aluminum calipers that often required them to be rebuilt with stainless steel sleeves. Nevertheless, the number of pistons in the caliper is not the determining factor of how well it works. How the caliper makes use of the effective pressure and disperses it across the brake pad makes one caliper better at applying more braking power than another. Calipers with six or more pistons are typically used for racing applications and their price reflects this. Most early model Corvettes can greatly benefit from a rebuilt aluminum caliper that has stainless steel sleeves and improved clamping force for use on stock rotors.
The Big PictureIf you're more serious about improving your Corvette's braking performance than simply adding new pads or rotors, you might be considering upgrading the entire system. Brake kits provide the best the aftermarket has to offer and can include stronger and larger-diameter rotors, improved calipers, and high-performance compound brake pads.
If you love your early '56-'62 Corvette enough to drive it frequently, upgrading from the factory drums to discs will definitely yield a dramatic improvement.
Just make sure the kit comes with, or has available, a dual master cylinder. This is necessary to provide adequate pressure to both the front and rear in the correct proportions.
Early models already equipped with front discs can also benefit from a variety of upgrade kits that include performance rotors, higher friction pads, and improved calipers. Some kits also allow you to upgrade your rear drums to discs, which in turn also require the correct master cylinder and booster to provide the appropriate proportion of pressure, front to rear.
Despite the fact that there are complete upgrade kits for the C4 and C5 models, it's hard to beat the factory brake system. The same calipers used on these models are part of a performance brake kit for many early model Chevelles and Camaros. Although the factory system is great for stopping your C5 from 120 mph, tests have shown small gains in stopping performance over the factory system are possible. Some of the aftermarket kits for these models include six-piston calipers and two-piece slotted and drilled rotors that are larger in diameter and are used with higher-friction matrix pads. On average, stopping distances with a new caliper, rotor, and pad system will usually improve by about 16-20 percent on early model Corvettes, 8-10 percent on late-models.
The use of stainless braided hoses may seem like a small matter, but they will last longer and ensure that the higher amount of brake pressure reaches the caliper. They also eliminate the possibility of swelling or cracking, a common problem with rubber hoses as they age.
No matter what you choose to upgrade your Corvette's braking, investigate the parts you're considering and make sure they apply to your specific application. You can piece together a bunch of rotors, calipers, and master cylinders from some fullsize Chevys that might fit your early Corvette, but the combination will not work correctly as a set of matched components. Also keep in mind that some complete systems can only be used with larger-diameter wheels, while others must be used with a specific pad that can be difficult to find or is available only from one manufacturer. Although most aftermarket brake manufacturers create products that meet or exceed the Department Of Transportation guidelines, there are some products that don't. Talk to various manufacturers to find out which kit is best for your Corvette and your specific application. One of the biggest mistakes is purchasing an extreme high-performance racing kit that works great at the track but lacks low-speed performance, with pads that cost more than a performance street version.
If you're installing new components yourself, such as new calipers and brake lines, remember to properly bleed the system. Late-model Corvettes equipped with ABS require the use of an ABS scan tool that cycles the system's solenoids to properly remove any air bubbles within it. High-performance brakes also require high-temperature brake fluid. Use a DOT 4 or higher brake fluid, but never mix a silicone fluid with standard polyglycol-based fluids. By following some of these steps, you can get your Corvette to stop quicker, no matter how fast you love to drive.
For an in-depth look at a C4-to-C5 brake conversion from Vette Brakes & Products, see "Braking For A Good Cause" in our June issue.