Maybe it is just the sheer number of brake jobs being performed in the aftermarket, but few if any single service categories generate as much discussion.
The brake job, done well, goes virtually unnoticed by the consumer, but the slightest misplay between components — the faintest of chirps — can bring the customer back to the shop.
What follows could be either an easy solution or a difficult warranty push-and-pull, but it is always something best avoided.
Various sources all seem to point to the same causes of the unsatisfactory, usually noisy, result: incomplete service.
One of the key shortcomings of a brake job gone bad is failing to replace brake hardware. Manufacturers have noted that, in cases where hardware is supplied with brake friction, that hardware sometimes returns unused alongside the brake pads in warranty claims. This isn’t always the case, but in such instances it is clear that the technician involved has not understood the importance of replacing hardware.
Disc brake hardware includes anti-rattle clips and springs, that secure pads in the caliper and prevent brake noise; guide pins on floating calipers that support and attach the caliper to the anchor plate; guide boots that protect them from corrosion; bushings and insulators that cushion caliper movements and help eliminate brake noise; and the caliper support key on some floating calipers that is used to locate and support it.
Drum brake hardware includes shoe return springs that retract shoes from the drum; hold-down springs that hold shoes on the backing plate; hold down pins that hold the shoe in place on the backing plate; and the automatic adjuster, which compensates for friction material and drum wear.
In today’s brake systems (actually in those produced for some time now), smaller rotors and lighter components have subjected hardware to significant heat cycling. Virtually any parts that are designed to hold brake parts in place have a useful life only as long as they can maintain sufficient spring tension.
Significantly, proper brake service also includes proper use of high temp silicone lubricant. Apparently, it is not uncommon for items being returned for dragging, premature wear, or binding to arrive completely dry, without any evidence of lubricant having been used. Make sure to look up and use only the recommended caliper lube procedure. Keep in mind that all manufacturers have very specific lubrication procedures. This lubrication is necessary to prevent vibration-induced noise.
Failure to employ these procedures has become grounds to refuse warranty claims, which is something that all professional counterpeople should be aware of.
Even when hardware is replaced and the proper lube employed, a caliper or set of pads may not be free to move, owing to a build-up of corrosion on a bracket.
Sometimes this can be very stubborn to remove, requiring a chisel or perhaps even the use of a rotary abrasive and a drill.
The key point is that all surfaces must be clean, in good condition, and properly lubricated if they are to allow the caliper and pads to move freely.
Pads must mate properly with rotors to provide proper braking performance, but the surface of the rotor must also be considered. In addition to the requirement that runout be within specifications, the surface finish must also be rough enough to provide a good surface, but not so rough as to cause pads, particularly semi-metallic formulations, to “track.” This condition, where the pad follows the direction of finish outward then snaps back to the inner radius under tension from hardware, can cause a clicking noise.
The solution is to ensure a non-directional finish of a very fine nature, between 10 and 50 microinches.
Rotors should be washed with soap and hot water before installation, as solvent-type cleaners do not remove all machining dust, and because drying with compressed air usually results in oil contamination of the friction material. It is also very important to make sure that the wheel flange behind the rotor is free of any rust or debris. Failure to eliminate rust or debris will cause rotor “runout,” which, over time, will cause friction material to be transferred to the rotor surface.
It should also be noted that the poor condition of a caliper may not be outwardly visible. Corrosion of the inner surfaces of the caliper from water-bearing brake fluid can lead to a “lazy caliper” condition. In cases such as this, it may be advisable to replace the caliper with a bare unit, or a semi-loaded option, which saves time and provides the assurance of a well-functioning unit.
Once service is performed, it is important for the technician to complete the job with proper break-in procedures. While some shops rely on the consumer for this, it is not a reasonable expectation that the car owner will understand either the importance of performing 30-50 moderate stops from speeds lower than 60 km/h, never mind how to properly execute the procedure.
Overall, the goal of complete brake service is to end up with a quiet, well-performing stopping system that keeps the customer happy. The parts, tools, and supplies are available. Whenever there is a doubt, technicians should be reminded to use them.
Information from a variety of sources was used in creating this article, including the Affinia Group, Federal-Mogul, BrakeQuip Corporation, and Honeywell Friction. Special thanks to Pierre Lalonde, senior technical specialist, Affinia Canada, and Fred Anderson, president, BrakeQuip, for their additional input.
Inspect Hydraulic Components
With all the attention paid to brake friction formulations, sophisticated ABS components, and the proper inspection of brake fluid condition, it is surprising how little attention is paid to the hydraulic lines that connect them all.
There is hard plumbing and soft, flexible plumbing.
On the hard lines, rust can be working its way from the inside out. A typical line may last six years, though it could be more or less depending on the condition.
At the OE level, some engineers have stated that hoses should last the life of the vehicle, but there is evidence to suggest that, as a result of moisture in the brake fluid, and the consequent rusting of the steel brake lines, even rubber hoses wear from the outside in.
If this is a new concept, consider that heater and radiator hoses have been shown to do just that, and it is now an accepted practice to consider that a hose may be on the verge of failing although it may look fine from the outside.
Aside from the complete failure of the hose itself, however, damage to hoses and lines from rough service, as well as corrosion and impact damage to vulnerable crimped fittings, can also be a cause for concern. Technicians should be advised to inspect lines for their integrity and condition–such as excessive rust or cracking–while performing brake service.