Brake Discs Buying Guide

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Brake Discs Buying Guide

When driving, whether it is around town or on the highway, it is important to be safe. And, while one can never predict the actions and reactions of other drivers in this respect, taking precautionary measures goes a long way in maintaining safety on the road. Minimally, this means practising basic defensive driving techniques whilst also maintaining the integrity of one's vehicle in a manner which ensures the safe performance of driving-related tasks. In general, this means paying attention to key systems such as one's suspension, tyres, and brakes.

Proper maintenance of a vehicle's safety system involves some basic knowledge about these key systems as well as a familiarity with their components and how they can fail. When it comes to brakes, understanding the theory behind how they work with a car is step one. Next, each piece of the puzzle must be further explained. This means, when looking to buy brake discs, for example, one must begin by knowing what they are and the types which are available. Once this basic knowledge is in place, the buying process for brake discs can begin.

Braking Theory

Understanding the basic theory behind a car's braking system is step one in learning how to choose replacement parts, such as brake discs. A complete understanding of braking theory involves both the ideal process, or how brakes work in theory, as well as a rundown of what goes wrong with one's brakes and why.

How Brakes Stop Cars

In the simplest of terms, the function of a car's brakes is to create friction through grabbing one part with another. This friction transfers the energy of forward motion into heat and thereby reduces the forward or backward momentum of the vehicle. In more complex terms, this process is the perfect example of the first law of thermodynamics: Energy can never be created nor destroyed, but merely transferred from one form to another. In the example of a car's brakes, kinetic energy (motion) is converted to heat. Specific parts are used to transfer this energy, and it is the friction created by those parts, which are a car's brake pads or brake shoes against the brake discs, that creates heat.

How Brakes Fail

Because each part of a braking system is so essential, there are a number of ways in which that system can fail. The key to maintaining one's braking system is being able to recognise each of these failures and properly replace the parts necessary.

Wear Limits

The first way in which a braking system fails has to do with the wear related to its component parts. Worn out brakes are incapable of creating the friction necessary to transfer kinetic energy to heat. This wear can take place on any part of the braking system, but is most commonly found on the brake pads or brake discs, each of which wear out a little bit every time the brake pedal is depressed.


Deflection is the next way in which a braking system fails. Deflection refers to the way in which one's brake system flexes or succumbs to the forces which are at work within the system. Problems with deflection can stem from the brake pedal link, calliper flexing, line expansion, or any other action which reduces force exerted against brake pads or shoes.

Force and Temperature

Though they are technically two separate reasons that brakes fail, force and temperature work together in many cases. Here is an example: When a driver depresses the brake pedal as hard as he or she can without an effect, the brakes have 'faded'. Fading brakes occur when the brake pads and discs cannot dissipate heat at a rate sufficient to slow forward momentum. Generally, this means that the surface temperatures of one or both braking components have exceeded the range necessary for proper operation.

Brake Discs Defined

After understanding the basic function of a braking system, the next step in purchasing the components, in this case brake discs, is to understand those components individually. This means first acquiring a basic definition of the components and then branching out into the specific types which are available.

What Is a Brake Disc?

Physically speaking, a brake disc is a round, flat metal piece which attaches to the wheel of a car. In concert with the brake pads and shoes, brake discs are responsible for stopping one's car. This is accomplished through a series of actions which begin with the brake pedal inside of the car. When depressed, the brake pedal exhibits a clamping force upon the brake discs through the brake pads. This is what creates the friction needed to stop the car's forward momentum as discussed above.

Problems arise with the brake discs when the repeated force of braking the vehicle causes them to wear. Generally, it is the brake pads which wear first. However, worn pads that are not properly replaced can subsequently wear out brake discs. At first, these discs can simply be turned to prolong their lives, but eventually the wear on the discs causes them to crack, warp, or shatter, leading to complete brake failure while driving. This is why it is so important to monitor one's brake discs and replace them appropriately.

Types of Brake Discs

There are four basic types of brake discs used in cars. Most privately used vehicles simply require standard brake discs. However, before one begins the shopping process, it is important to know what the other types of discs do and why they may or may not be appropriate for a particular car. The four types of brake discs, defined in the table below, are standard, cross-drilled, slotted, and cross-drilled and slotted brake discs.

Type of Brake Disc

Main Usage

Brake Pad Required


Standard Brake Disc

City-driven and commuting cars; can be used for racing cars with proper pads

Any type

Fairly inexpensive; does not prematurely wear a brake pad

Cross-Drilled Brake Disc

City-driven and commuting cars

Any type

Does not contribute to premature pad wear; available with corrosion-resistant coating to prevent rust

Slotted Brake Disc

Racing vehicles; can be used for daily driving

Out-gassing brake pad for racing; any pad for daily driving

Available with corrosion-resistant coating to prevent rust

Cross-Drilled and Slotted Brake Disc

Street-driven cars only

Any type

Very aggressive-looking brake disc which is usually combined with an open-designed wheel

Clearly, each of the types of brake discs mentioned above can be used on privately used cars. However, as one moves down the table, the options increase in price, sometimes significantly. Therefore, a buyer simply interested in fixing his or her brakes is best off with the standard model, whereas the person looking to customise his or her car or to use the car for racing is more likely to look into the other types of brake discs.

Buying Brake Discs on eBay

Once a buyer understands all of the basic functions of a car's brakes as well as the brake discs specifically, the process of searching for brake discs and eventually replacing them can begin. Brake discs are common auto parts which are widely available for purchase through automotive retailers as well as online stores and marketplaces such as eBay. However, the process of searching for brake discs can seem intimidating at first, which is why eBay is the best option for finding exactly the brake discs you need at a great price.

Searching eBay for Brake Discs

Like many auto parts, brake discs are made specifically for the make and model of vehicle on which they are used. Therefore, learning how to search eBay for brake discs is the first step in saving time and money through shopping on this site.

eBay makes the search process simple by providing a general search bar at the head of every page on its website. Through this search bar, a buyer can enter general or specific terms to meet his or her needs. Since brake discs are specific to one's vehicle, match the search terms accordingly. Thus, entering "Audi brake discs" yields a good result, but "Audi Quattro brake discs" is even better. A buyer may also want to consider entering the specific brand of brake discs wanted as well. Some popular choices are Mintex, Brembo, and EBC.


There is a saying that one can never be too rich or too thin and when speaking of cars, it seems appropriate to add that one can never be too safe. This is why defensive driving techniques along with the proper maintenance of one's vehicle's major systems are essential. Among these important systems is one's braking system. Working based on the first law of thermodynamics, the component parts of the braking system convert kinetic energy into heat in order that the car is slowed at a reasonable rate. However, problems with any one of these component parts can lead to failure, the opposite of safety.

A car's brake discs are an important component of the braking system, which work along with its brake pads to convert kinetic energy to heat and slow the car. Worn brake pads, however, fail to do this and directly lead to system failure. Therefore, monitoring one's brake discs and replacing them with the proper type, standard, cross-drilled, slotted, or cross-drilled and slotted, is essential.

When it comes to buying one's replacement brake discs, there are many options from auto parts stores to online. However, eBay, with its simple searching system, allows a buyer to quickly locate the type of brake discs needed in a fraction of the time whilst concurrently offering competitive prices that save the buyer money.

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