What is the description of brake pads?

Component of disc brakes

With competitive price and timely delivery, ALLMAX sincerely hope to be your supplier and partner.

Brake pads are a component of disc brakes used in automotive and other applications. Brake pads are composed of steel backing plates with friction material bound to the surface that faces the disc brake rotors.

Function

[

edit

]

Brake pads convert the kinetic energy of a vehicle to thermal energy through friction. Two brake pads are contained in the brake with their friction surfaces facing the rotor.[1] When the brakes are hydraulically applied, the caliper clamps or squeezes the two pads together onto the spinning rotor to slow and stop the vehicle. When a brake pad heats up due to contact with the rotor, it transfers small amounts of its friction material onto the disc, leaving a dull grey coating on it. The brake pad and disc (now both having the friction material), then "stick" to each other, providing the friction that stops the vehicle.

In disc brakes, there are usually two brake pads per disc rotor, they both function together. These are held in place and actuated by a caliper affixed to the wheel hub or suspension upright. Racing calipers, however, can utilize up to six pads, with varying frictional properties in a staggered pattern for optimum performance. Depending on the properties of the material, the weight of the vehicle and the speeds it is driven at, disc wear rates may vary. The brake pads must usually be replaced regularly (depending on pad material). Most brake pads are equipped with a method of alerting the driver when this needs to be done. A common technique is manufacturing a small central groove whose eventual disappearance by wear indicates the end of a pad's service life. Other methods include placing a thin strip of soft metal in a groove, such that when exposed (due to wear) the brakes squeal audibly. A soft metal wear tab can also be embedded in the pad material that closes an electric circuit when the brake pad wears thin, lighting a dashboard warning light.

History

[

edit

]

The concept of brake pads or disc brakes as an alternative to drum brakes had been around at least as early as a patent by F. W. Lanchester in .[2] However, due to high cost and inefficiencies compared to drum brakes they were not commonly implemented until after World War II.[3] Once disc brake technology improved, brake performance quickly surpassed that of drum brakes. The performance difference was most noticeably exhibited in when a Jaguar outfitted with brake pads won the 24 Hours of Le Mans Grand Prix of Endurance race.[3][4] The success of the Jaguar is commonly attributed to the car's disc brakes, which allowed the drivers to approach turns faster and brake later than their opponents, which ultimately led to its victory. As late as the majority of automobiles using disc brakes were European made, with American cars adopting the technology in the late s after the invention of fixed calipers that made installation cheaper and more compact.[3]

Technology

[

edit

]

Disc brake advantages

[

edit

]

Disc brakes offer better stopping performance as compared to drum brakes. They provide better resistance to "brake fade" caused by the overheating of brake pads, and are also able to recover quickly from immersion (wet brakes are less effective). Unlike a drum brake, a disc brake has no self-servo effect'the braking force is always proportional to the pressure applied on the braking pedal lever. However many disc brake systems have servo assistance ("Brake Booster") to reduce the driver's pedal effort.[citation needed]

Disc brake pads are easier to inspect and replace than drum brake friction lining.

Types

[

edit

]

A set of pads for high-performance disk brakes

There are numerous types of brake pads, depending on the intended use of the vehicle, from very soft and aggressive (such as racing applications) to harder, more durable and less aggressive compounds. Most vehicle manufacturers recommend a specific kind of brake pad for their vehicle, but compounds can be changed (by either buying a different make of pad or upgrading to a performance pad in a manufacturer's range) according to personal tastes and driving styles. Care must always be taken when buying non-standard brake pads as the operating temperature ranges may vary, such as performance pads not braking efficiently when cold or standard pads fading under hard driving. In cars that suffer from excessive brake fade, the problem can be minimized by installing better quality and more aggressive brake pads.

Materials

[

edit

]

The most important characteristics that are considered when selecting a brake pad material are as follows:

Another material requirement that is considered is how compressible the brake pads are; if they are too compressible then brake travel or brake booster fluid displacement can be excessive.[7] Brake pad material must also be porous to minimize the effect water has on the friction coefficient.[7]

Asbestos was added as a common ingredient to brake pads post-WWI, as car speeds began to increase, because research showed that its properties allowed it to absorb the heat (which can reach 500 °F) while still providing the friction necessary to stop a vehicle.[8] However, as the serious health-related hazards of asbestos eventually started to become apparent, other materials had to be found. Asbestos brake pads have largely been replaced by non-asbestos organic (NAO) materials in first world countries.[9] Today, brake pad materials are classified into one of four principal categories, as follows:

• Non-metallic materials - these are made from a combination of various synthetic substances bonded into a composite, principally in the form of cellulose, aramid, PAN, and sintered glass. They are gentle on rotors, but produce a fair amount of dust, thus having a short service life.
• Semi-metallic materials - synthetics mixed with varying proportions of flaked metals. These are harder than non-metallic pads, more fade-resistant and longer lasting, but at the cost of increased wear to the rotor/drum which then must be replaced sooner. They also require more actuating force than non-metallic pads in order to generate braking torque.
• Fully metallic materials - these pads are used only in racing vehicles, and are composed of sintered steel without any synthetic additives. They are very long-lasting, but require more force to slow a vehicle while wearing off the rotors faster. They also tend to be very loud.
• Ceramic materials - Composed of clay and porcelain bonded to copper flakes and filaments, these are a good compromise between the durability of the metal pads, grip and fade resistance of the synthetic variety. Their principal drawback, however, is that unlike the previous three types, despite the presence of the copper (which has a high thermal conductivity), ceramic pads generally do not dissipate heat well, which can eventually cause the pads or other components of the braking system to warp.

  [

  5

  ]

  However, because the ceramic materials cause the braking sound to be elevated beyond that of human hearing, they seem exceptionally quiet.

  [

  10

  ]

Phenol formaldehyde resin is frequently used as a binding agent. Graphite can serve as a friction material as well as binding agent.[11] Another friction material commonly used is zirconium silicate.[9] An Italian producer is conducting research to use cement as a cheap and less energy-intensive binding agent.[12] The table below outlines the make up of a common brake pad.[9]

Constituent % by weight Whiting (Chalk) 31.6 Bronze powder 15 Graphite 10 Vermiculite 16 Phenolic resin 16 Steel fibres 6 Rubber particles 5 "Friction Dust" 5 Sand 3 Aramid fibres 2

There are environmental factors that govern the selection of brake pad materials. For example, the bill SSB [13] adopted in Washington State in limits the amount of copper that is allowed to be used in friction materials, to be eventually phased out to trace amounts, due to the negative impact of high copper levels on aquatic life. For its substitution, different material combinations have been developed, though no direct replacement is available yet.[14] Other materials, such as compounds made with antimony, are being studied.

Contact us to discuss your requirements of brake pad advertisement supplier. Our experienced sales team can help you identify the options that best suit your needs.

Additional reading:
Why choose SHACMAN F3000 over competitors?
Top 10 Electric Vehicle Manufacturers in China
Shacman Mixer Truck: Top 5 Features You Need to Know!
Top 5 Benefits of Using JX0818 Oil Filter for Agricultural Machinery
Top Car Washer Wholesale Deals You Can't Miss
Top 5 Reasons to Choose Shacman Heavy Duty Trucks Today
How Does oil filter factory Work?

Vehicles have different braking requirements. Friction materials offer application-specific formulas and designs. Brake pads with a higher coefficient of friction provide good braking with less brake pedal pressure requirement, but tend to lose efficiency at higher temperatures. Brake pads with a smaller and constant coefficient of friction do not lose efficiency at higher temperatures and are stable, but require higher brake pedal pressure.

Maintenance and Troubleshooting

[

edit

]

Brake pads should be checked at least every 5,000 miles for excessive or uneven wear. Although brake pad wear is unique to each vehicle, it is generally recommended that brake pads be replaced every 50,000 miles.[6]

Malfunctions with brake pads can have many effects on the performance of a vehicle. The following chart outlines some common issues that can be caused by brake pad malfunctions:[8]

Issue Possible Cause Braking requires an abnormal amount of force

on brake pedal

Worn brake pads, contaminated brake fluid, faulty brake caliper, faulty master cylinder, loss of vacuum, loss of brake fluid Car pulls to one side when braking Faulty brake caliper, restriction in hydraulic system, brake pad lining(s) contaminated with oil or brake fluid, brake pads not replaced in pairs, brake pad not fitted correctly, Poor braking performance Brake pad lining(s) soaked with water, oil, or

brake fluid; Overheated brake pad linings, worn brake pads, faulty master cylinder, brake fluid leak, air in brake fluid, misadjusted brake shoes, boiling brake fluid

Sensitive braking Incorrect brake pad linings; Greasy brake pad linings, faulty proportioning valve, misadjusted master cylinder pushrod Noisy braking (grinding or screeching sounds

when braking)

Extremely worn brake pads, brake pad(s) not fitted correctly, faulty or missing brake pad shim, brake pad wear indicator Vibration under braking Contaminated rotors or pads, warped rotors, out of round drums, ABS activation

Testing of Materials

[

edit

]

The National Bureau of Standards (NBS) started testing of brake material in the US in . The testing setup was then shared with manufacturers who wanted them so that they could begin to test their own products.[15] Over time the NBS continued to develop new instruments and procedures for testing pads and lining, and these standards eventually became the standards for the American Engineering Standards Committee's Safety Code for Brakes and Brake Testing.[15]

SAE J661 testing is used to determine the friction of different brake pad materials by testing a 1 inch (25 mm) square liner with a brake drum. This testing yields values for both hot and cold coefficients of friction, which are then paired with letter designations.[7] The table below outlines what letter goes with each range for the coefficient of friction. An example of the designation would be "GD", where "G" is the normal coefficient, while the "D" represents heated.[7]

Letter Designation for Friction Coefficients C <0.15 D 0.15 to 0.25 E 0.25 to 0.35 F 0.35 to 0.45 G 0.45 to 0.55 H >0.50 Z unclassified

Cataloguing

[

edit

]

There are different systems for the cataloguing of brake pads. The most frequently used system in Europe is the WVA numbering system.[16]

The cataloguing system used in North America, and recognized around the world, is the standardized part numbering system for brakes and clutch facings issued by the Friction Materials Standards Institute (FMSI). FMSI's mission is to, "Maintain and enhance this standardized part numbering system for all on highway vehicles in use in North America."[17]

Cartridge brake pad

[

edit

]

A type of brake pad used on rim brakes.

See also

[

edit

]

References

[

edit

]

Thankfully, Fred Flintstone-style brakes are a thing of the past! If they weren't, can you imagine how red lights and stop-and-go traffic would wear out the pads of your feet? Nowadays, a light press on the brake pedal can slow your vehicle to a complete stop, all thanks to the complexities of your braking system. Like other parts of your car that go to work every day, your brakes are prone to wear out over time'especially your brake pads. Learn more about your car's brake pads so you can stay in-tune with their care and maintenance, plus head-off any brake problems before your brakes decide to "take a break!"

When were brake pads first invented?

Up until the s, most cars relied on a wooden block to brake. The driver pushed a lever that in turn, rubbed the block against the wheels, creating friction and stopping the vehicle. As cars started going faster (above 10-20 mph) and wheels became more complex, the wooden block ceased being the most efficient braking method. In , inventor Elmer Ambrose Sperry designed the first solution: a car equipped with front-wheel disc brakes and brake pads that "pinched" the rotor or disc, working much like bicycle brakes.

How do modern day brake pads work?

Simply put, brake pads contact your rotors and cause friction to slow and stop your car. Brake pads are part of a very interconnected system, a system that relies on each of its parts to function safely and successfully. Here's how your brake pads play their part:

• When you press down on the brake pedal, you activate a cylinder that sends brake fluid through hoses, down to the calipers.
• The calipers engage your brake pads.
• Your brake pads apply pressure to the rotor, which is directly connected to each wheel.
• This pressure creates the friction needed to slow or stop your vehicle. When the rotor slows, so do your wheels.
• Take your foot off the brake pedal and the whole process reverses: the brake pads release, fluid moves back up the hoses, and your wheels are on the move again!

Psst! You can learn more about braking parts and processes in Everything You Need to Know About Brakes.

Are there brake pad problems I should watch out for?

Certain sounds and sensations can all signal potential brake pad problems. Stay alert and pay attention to:

• Screaming or grinding: Any noise that could be labeled as "eardrum piercing" could mean it's time to have your brake pads inspected. Worn pads could cause damage to other parts of the system and lead to major and often more expensive repairs.
• Shaking in your steering wheel or brake pedal: When worn brake pads turn into worn out brake pads, it can lead to rotor damage from all the metal-on-metal rubbing. Shivers and shakes in the steering wheel or brake pedal are more than just unpleasant. Your brake system is trying to communicate with you!
• Brake warning light: This dashboard indicator light could come on for several reasons, none of which you want to ignore. The light could be clueing you into a problem with the brake's hydraulic system, your brake fluid level could be low, or your parking brake may be engaged. Whatever the reason for the light, your ability to safely come to a stop isn't worth risking.

How often should my brake pads be inspected?

General wisdom says to have your brakes (including your brake pads) inspected every 5 months or 5,000 miles, but your manufacturer guidelines may give you better guidance for your specific vehicle. If you're hearing grinding, squeaking, or squealing, your steering wheel feels shaky, or your brake warning light is on, visit your nearest Firestone Complete Auto Care today. During a free brake inspection, we'll measure your brake pad wear, check brake fluid levels, and let you know if your brakes need further service. Our technicians are ready to answer your brake questions and give you a better idea of how much "life" is left in your car's brake pads. If you're ready to stop wondering what's troubling your brakes, visit your local Firestone Complete Auto Care or schedule an appointment online for a free brake inspection today.

Are you interested in learning more about Brake Lining bulks? Contact us today to secure an expert consultation!