It is often said that brake pad manufacture involves more art than science, but this is generally not true.

In fact, with more than 2000 materials and substances that are available to brake pad manufacturers, a scientific approach to brake pad manufacture is a requirement and luck can therefore have no part in the formulation of brake pad friction materials. Thus, if you have ever wondered what ingredients, substances, and materials go into the making of modern, high-quality brake pads, this article will answer all the questions you have ever wanted to ask, starting with answering this question:


Are Aftermarket Brake Pads just as good as OEM?

As with everything else in life, you get what you pay for, but in the case of Bendix brake pads, your customers pay for brake pads that meet, and often exceed OEM specifications in terms of durability, reliability, and smooth, silent operation.

In fact, Bendix brake pads include several proprietary technologies such as their Blue Titanium Stripe that eliminates bedding-in, and Stealth Advanced Technology that ensures the optimum pad/rotor contact area to prevent overheating and brake fade in applicable applications.

Given the above, it is fair to say that Bendix ranks high among the aftermarket brake pad manufactures that meet, and often exceed OEM brake pad performance levels on a consistent basis, so yes, aftermarket brake pads often outperform OEM brake pads, provided you fit Bendix brake pads to your customers’ vehicles.

So, what goes into a Brake Pad?

While brake pad manufacturers never publish the exact formulations of their brake friction materials, and are in many jurisdictions not obligated to, this article can only provide an overview of the materials that are most commonly used in brake pad manufacture. Consider the chart below.


This chart is the result of diligent research, and it that shows the average percentages of the main categories of materials that are most commonly included in the products of most reputable brake pad manufacturers. As stated elsewhere, brake pad manufactures have a list of more than 2000 substances they can use legally, but since limited space precludes listing all 2000 substances here we will cover only some of the most commonly used materials, and explain what functions these substances have in the overall formulation of brake pad friction materials, starting with-

Binders

• Fibre glass functions both as a binding agent and a structural material, and can comprise between 5% and 25% of the total volume of the friction material, depending on the application
• Phenolic resins are most commonly derived from cashew nut shells, and functions as both binding agents and performance enhancers. These resins typically account for between 10% and 20% of the total friction material volume, depending on the application

Abrasives

• Mineral fillers derived from quartz or synthesised silicates are used as abrasives to enhance friction, and can account for between 5% and 35% of the total volume. Note that mineral fibres are typically not used in metallic brake pads
• Oxides of various metals, typically iron oxide and aluminium oxide, function as both abrasives and fillers/binders in metallic and semi-metallic brake pads. Note that it is almost certain that even so-called “organic” brake pads will contain a small percentage of metallic oxides. Depending on the application, oxides of metal can account for up to 70% of the total volume of the friction material
• Brass filings or chips are used to boost friction in wet conditions. Depending on the application, brass chips can account for up to 5% of the total volume of the friction material
• Pure carbon fibre is used as both an abrasive and a binder in mostly racing brake pads, although minute quantities of carbon fibre is present in some performance oriented aftermarket brake pads, with the price of the brake pads being a somewhat reliable indicator of how much, or how little carbon fibre is present in the pads.

Performance enhancers

• Cashew resin derived from cashew nut shells is used to resist brake fade, and to reduce, if not eliminate brake squeal. Depending on the application, cashew resin can account for up to 20% of the total volume of the friction material
• Carbon in various forms exists in most brake pads, and it is commonly used as both a cheap friction booster and/or a lubricant, depending on the application. Carbon can account for up to 30% of the total volume of the friction material
• Metal sulphides such as copper sulphide, lead sulphide, or antimony sulphide are used to stabilise friction coefficients across a wide range of brake operating temperatures. Depending on the application and the particular sulphide(s) used, sulphides can account for up to about 30% of the total volume of the friction material
• Calcium hydroxide (lime) is used as a rust inhibitor in both metallic and semi-metallic brake pads
• “Friction powder” is a generic term that applies to proprietary blends of several (usually unspecified) compounds that all brake pad manufacturers use for a wide variety of purposes and functions. Typically, though, friction powder is used as a flame retardant, friction modifier, lubricant to reduce dust creation, and brake noises. There is no verifiable information available on the average friction powder content of high quality brake friction materials

Fillers

• Fillers such as barium sulphate, potassium titanate, common household steel wool, and rubber derived from recycled tyres are commonly used to bulk up the total volume of a friction material formulation. Although the filler content of brake pads vary widely, these substances are used mainly to increase the wear resistance of brake pads

Structural enhancers

• Mineral-based fibres that are spun from alumina, silica, calcia, magnesia, and vermiculite are commonly used to strengthen the overall structure of brake pads, although these fibres are also used to resist brake fade caused by high brake temperatures. Depending on the application, mineral fibres can account for between 10% and 20% of the total volume of the friction material, but note that mineral fibres are typically not used in metallic brake pads
• Ceramic materials occur in an enormous variety, and provided that any given brake pad contains actual ceramic material and not common clay, the ceramic component of the pad can fulfil any of the functions any of the other substances listed here, and in some cases, a brake pad can consist of nothing but highly refined ceramic. However, the problem with ceramics is that many brake pad manufactures define the word “ceramic” very loosely, with the result that many semi-metallic and even some organic brake pads are labelled as “ceramic” when in fact, there is no, or very little ceramic materials present in the pads.
• Copper is commonly used in ceramic brake pads in small percentages to prevent brake fade, but also as a lubricant to reduce brake noise. Note though that since the use of copper in brake friction material has been banned in some jurisdictions, copper may have been replaced in some friction material formulations by hexagonal boron nitride
• Kevlar in various forms is used in some specialised applications as a friction booster, but there is no verifiable information available regarding other possible uses. Note though that very few, if any brake pad formulations contain more than about 3% Kevlar.

At this point, astute readers will have noticed two things; the first being that the number of friction material ingredients listed above represents only a small fraction of the possible total, and the second being that the numbers listed above do not add up to 100%. The latter point is because no brake pad manufacturer will ever list complete lists of ingredients and percentages, but despite this, the items and numbers listed above cover the most ground, which brings us to-