BY Larry Carley

When replacing brake system components in today?s vehicles, technicians should make every effort to make sure the level of safety and performance of the vehicle remains the same as designed by the vehicle manufacturer. This means installing high quality replacement parts that meet or exceed the design criteria and performance of the original equipment parts. Following this advice will not only restore the brake system to "like-new" condition, but also enable it to meet the same safety criteria as the OEM brakes.

Brake systems on all new vehicles must meet minimum performance standards established by the National Highway Transportation Safety Administration (NHTSA). FMVSS105 and FMVSS135 are the government?s standards that specify required stopping distances, fade resistance and so forth for new cars and trucks.

What many motorists, technicians and parts professionals do not know is that the FMVSS standards apply to new vehicles only. Aftermarket brake parts currently do not have to meet the FMVSS standards - or any other performance standards. Consequently, many people mistakenly assume that all brakes parts are equal.

What?s more, they assume that installing such brake parts will not have an adverse effect on the stopping distance, fade resistance, brake balance or handling characteristics of their vehicle.

The fact is some aftermarket replacement brake parts do not meet OEM design and performance criteria, and are not capable of meeting the FMVSS requirements. Installing parts that deviate from OEM design specifications can upset brake balance, increase the risk of rear wheel lockup and skidding when braking hard (especially on wet or slick surfaces), increase the risk of brake fade when the brakes get hot, and even affect steering stability, alignment and handling. These shortfalls could create a serious safety issue in certain driving situations. That is why replacing the original component with one that meets or exceeds the design criteria of the vehicle manufacturer is recommended to maintain brake safety and performance.

The last thing any brake technician should ever do is install brake parts that compromise safety. Yet it happens every day because there is no law that prevents the use of aftermarket brake parts that do not meet OEM specifications or FMVSS standards. In light of the recent problems Firestone has experienced with some of their tires, NHTSA may have to reexamine its current policies towards vehicle safety standards, including aftermarket brake parts.

The recommendation to install replacement parts that meet or exceed the original equipment applies to friction materials, as well as hydraulic components, rotors, drums and other brake hardware. Most brake suppliers offer "application specific" or "application engineered" replacement linings that closely match friction characteristics of OEM brake lining on various vehicle applications. In some cases, the aftermarket lining material may actually be different than the original (a ceramic based material, for example, instead of a semi-metallic). But the friction characteristics are similar to maintain the proper brake balance, feel, stopping performance and fade resistance.

With brake rotors, substituting one-piece cast rotors for composite rotors may also be a concern. Composite rotors have a thin, stamped steel center hat that supports the cast iron disc. The design reduces weight, but makes the rotor more difficult to resurface because it is less rigid than a cast rotor. Composite rotors are also more costly to manufacture, so some brake suppliers offer one-piece cast replacement rotors for many applications that were originally equipped with composite rotors.

Swapping a cast rotor for a composite rotor may seem like a simple fix. But if a cast rotor is installed on one side and the vehicle still has a composite rotor on the opposite, it can upset alignment geometry, increase tire wear and may cause a steering pull. The added thickness of the thicker hat section in a cast rotor relocates the wheel further out from the knuckle. This changes the scrub radius of the suspension, which can cause the vehicle to lead toward the side with the most scrub radius. The thicker rotor will also alter toe and camber alignment, which will accelerate tire wear. Installing cast rotors on both sides will equalize the change in scrub radius, but it still changes toe and camber (which must be reset to prevent abnormal tire wear).

Some low quality rotors may also have dimensional differences that cause installation hassles or interference problems with the caliper or wheel. Some rotors may be made of a lower grade of cast iron and/or have a surface finish that does not have the same friction characteristics as the original rotor. This may cause a brake pull if the rotor is used on one side only, or increased stopping distance even if both rotors are replaced.

Other differences to watch out for include replacement master cylinders, calipers and wheel cylinders made of cast iron instead of aluminum. Aluminum castings are anodized for corrosion resistance. Substituting and uncoated cast iron part can increase the risk of internal corrosion caused by moisture contaminated brake fluid. The difference in weight may also cause problems. Some plastic brake boosters may experience fatigue cracking if a heavier cast iron master cylinder is mounted on the unit. Heavier calipers may increase ride harshness and steering feedback.

By installing high quality replacement parts, the possibility of creating unforeseen problems is reduced. The brakes are one of the most important safety systems on a vehicle, so every effort should be made to make sure the level of safety and performance that was originally designed into the system by the vehicle manufacturer is not compromised.