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Big Brake Upgrade

Size matters, but so does thermal capacity

Out of all the upgrades and accessories on the market, one of the most practical items is one that you can't readily see—a front brake upgrade. Okay, maybe it won't turn heads like a new grille or faux woody treatment, but adding high-quality aftermarket brakes can greatly enhance your driving experience, especially if you have any bent toward performance.

Physics

The value of a larger brake package is not simply that it's bigger—though the rotors are indeed often much larger. The key benefit of a brake upgrade is the way it handles heat. Why is that so important? Brakes work by converting kinetic energy to thermal energy (heat), and transferring it by conduction, convection and radiation into the air stream.

Stopping distance alone is not the best measure of a brake system's effectiveness, since the tires and suspension can significantly affect this number. In fact, a new brake system may not significantly decrease stopping distance on a one-time test. More important to brake performance are factors such as consistency, repeatability, durability, balance, and resistance to fade. Improved thermal capacity—the ability to absorb and transfer heat—has a direct affect on all of these factors.

To that end, some aftermarket rotors have directional vanes that draw air into the rotor and accelerate it outward from the wheel. Brake rotor's vanes work like those on your car's water pump—the more efficiently they move fluid (or hot air), the better the heat dissipation.

An enormous amount of research and engineering goes into optimizing the air flow throughout the rotors, and can achieve as much as a 100% increase over stock discs, depending on the design. In addition to increasing heat transfer, an additional design goal is to maintain an even heat distribution to prevent coning or belling of the disc.

Aftermarket Benefits

Aftermarket brakes may have a lighter-weight, two-piece construction with air passages in the hat that are designed to minimize this type of distortion, which can occur in hard racing. The one-piece rotor shown in this installation does not have these passages but is recommended for street performance. The rotors on both kits are slotted on the face to prevent out-gassing of the pads when they get hot. These slots also help to clear debris and provide a better pad bite. One tip: Make sure the pads are readily available. The ones shown here are the same as those found on the ubiquitous Ford F-150 truck.

Aftermarket brake calipers may have more than one piston, which helps to distribute the clamping force better and/or increase it. In some cases, on a two-piston caliper, the rear piston is slightly larger than the front one in order to minimize pad taper (unequal wear and tendency to float). These different bore sizes are needed because more force is required on the rear piston in order to clear the debris field. If the total surface area of the pistons is only slightly greater than stock (less than 10%), it will probably not affect the front/rear balance.

Installation

Even though an aftermarket brake system may offer a number of technological improvements over the stock binders, installing it is often a straight bolt-in swap. The job shown here needed no additional modifications to the existing factory setup other than to use larger wheels to clear the aftermarket calipers.

Wheel weights clamped inside of the wheel may need to be repositioned for sufficient clearance. Actually, the more critical clearance is between the spokes of the wheel and the outer face of the caliper. Don't assume that an 18-, 19- or even a 20-inch wheel has sufficient spacing. Wheel backspacing also affects caliper clearance.

You can check the fit on the wheel before proceeding with the brake install by leaving the lines still attached to the stock caliper. Simply hang the stock caliper on the spring with a zip-tie to temporarily move it out of the way. On this PT Cruiser, wheel spacers up 3mm per side can be used without affecting suspension settings, but check for fender clearances if you lower the vehicle.

Resources

Moss Motors, Ltd., 805/681-3400, www.mossmotors.com

Stoptech, 310/325-4799, www.stoptech.com