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Brake Pads
Questions Answers
What causes brake noise and how does Bosch minimize it in their brake pads?

Brake noise can be caused by a number of different factors:

  • Pad edges engaging the rotor, causing chatter, vibration and noise
  • Vibration of rotors, pads and steel backing plates
  • Caliper piston vibrating against the brake pad steel backing plate
  • Vibrating shims can vibrate
  • Rusted steel backing plates

To reduce noise, Bosch Ceramic and Premium brake pads include:

  • The highest quality stainless steel shims. This provides the ultimate in corrosion resistance, durability and reliability, for longer noise-free performance
  • A patented graphite enhanced powder coating to protect the steel backing plate from corrosion. The coating provides protection in even the harshest environments, and can withstand temperatures up to 1100 degrees F. The powder coating is impregnated with graphite and helps the pad slide on the caliper housing to reduce noise
  • A slotted surface and chamfered edges for quiet operation – found only on premium quality linings. Chamfered edges allow the pads to engage the rotor more smoothly, which reduces chatter, vibration and noise. Slots also help dampen noise and allow a path for hot gases to escape under severe braking conditions
  • An exclusive underlayer that acts to absorb vibration while maintaining full stopping power. The underlayer is located between the pad and steel plate and acts to dampen any and all vibrations caused when brake pads engage the rotors
Brake pads work by applying pressure against rotors. Won’t all brake pads stop the same? All brake pads perform the same basic task — applying pressure against the rotors in order to stop the vehicle. However, not all pads are equal. Materials, formulas, design and craftsmanship can be dramatically different in brake pads. Tests have shown that Bosch pads outperform most competitors by a significant margin, requiring less stopping distance than other aftermarket brands of pads.
Should brake pads be broken in (driven gently for the first 200 miles in order for the pads to cure)? When some brake pads emerge from the oven, they are not yet fully cured. Residual chemicals and gases are still present in the friction material resin that must be removed before the pads are completely stable. Many aftermarket brake pads are sold in a “green” state (not fully cured) and require an initial break-in period after they have been installed. The risk with this approach is that too much heat too quickly can glaze and ruin the pads. Bosch pads are fully cured at the factory with a patented laser burnishing process. A precisely controlled laser beam is used to heat and condition the pad surface, eliminating the need for a traditional break-in period on the vehicle following installation.
What is involved in a complete brake job?

Complete brake jobs should cover every aspect of the system from the master cylinder to the calipers and wheel cylinders. This includes:

  • Checking the level and condition of the brake fluid. Changing the fluid is recommended to get rid of moisture contamination
  • Bleeding all the brake lines to remove trapped air
  • Inspecting the entire system for leaks (hoses, lines, wheel cylinders, calipers and master cylinder)
  • Inspecting all the mechanical and hydraulic components in both the front and rear brakes (calipers, caliper hardware, wheel cylinder, drum hardware and parking brake)
  • Replacing the front and rear linings (if necessary)
  • Inspecting and resurfacing or replacing rotors and drums as needed
  • Inspecting wheel bearings (repacking on older vehicles)
  • Lubricating all critical areas such as caliper slides and shoe pads with moly-based high temperature brake grease
  • Checking and adjusting the parking brake
  • Checking the ABS system (no warning light or trouble codes)
  • Making sure the pedal is firm and the brakes operate properly, quietly and provide safe stopping power once the job is complete
Is it OK to only install brake pads? “Pad slap” brake jobs (replacing the pads and nothing else) only invite trouble down the road; the brake system is your vehicle’s most important safety feature and checking the entire system is important. If the front disc brake pads are worn and need to be replaced, chances are other components in the brake system may require attention, too. The most obvious ones are rotors and calipers, but the rear brakes may need work also.
How important are rotors in the performance of brake pads? New disc brake pads require a clean, smooth flat surface on the rotors otherwise brake performance will suffer. A rough surface will accelerate pad wear and increase the risk of noise. An uneven surface or variations in rotor thickness can cause vibrations, noise and annoying brake pedal pulsation. When inspecting the rotors there should be no deep scoring or cracks, runout should be less than .003 in. (.060 mm) and thickness variation should be less than .0003 in. Look for discolored patches or hard spots on the rotor surface, replacement is the best repair option. Changes in metallurgy extend below the surface. Turning the rotor may temporarily restore a flat surface, but the harder metal will still be there and cause the rotor to wear unevenly. Within a few thousand miles the pedal pulsation will return. Measuring rotor thickness is an absolute must. If rotors are worn to less than the “discard” specification marked on the rotor, the rotor must be replaced. If the rotor cannot be resurfaced, without exceeding the minimum “machine to” thickness specification, replacement is also required. When rotors are resurfaced, care should be used to minimize runout. This may require measuring hub and rotor runout on the vehicle using a dial indicator (and indexing the rotor on the hub to minimize runout or installing a tapered shim behind the rotor to correct runout) or using an on-car lathe that cuts the rotor true to the hub. Ideally, rotor runout should be less than .001 in. on the vehicle or on a bench lathe.
How are ceramic brake pads different from semi-metallic brake pads? Ceramic brake pads incorporate a formula that includes ceramic materials and utilizes less metal (approximately 15% metal content by weight). Ceramic brake pads combine exceptional braking power with very quiet and low-dust braking. However, it is not recommended to use ceramic brake pads for towing applications. Semi-Metallic brake pads incorporate a formula that utilizes approximately 40% or more metal content by weight. Semi-Met brake pads offer premium braking power and work particularly well for towing applications.