Automobiles are complex machines. Many parts are assembled to form the various systems that work together to make cars and trucks run smoothly and safely. The exhaust system filters air and keeps the engine cool, while the fuel system provides the gasoline to power the engine. A battery powers the electric systems of a motor vehicle, and the brakes system enables the automobile to stop its forward motion. In order to slow and halt the movement of such a heavy machine, owners must maintain all components of the brakes system.
One such component is the brake disc. Brake discs are needed on each brake, which are part of the system that works with each wheel. Combined with the other elements, including brake pads and the actual brakes, brake discs are essential parts of the safe operation of all automobiles. Brake discs, like many automotive parts, experience wear or damage over time, regardless of their material or design and require replacement. Learning about the purpose of brake discs and the various available types, as well as how to find and purchase brake discs on eBay, allows one to make a wise and safe buying decision.
The Purpose of Brake Discs
Brake discs are one component of the disc brake system, which also includes brake callipers and brake pads. The disc brake system slows the wheels' rotation through the use of friction. The brake pad is pressed against the brake disc with a set of callipers. This style of brakes was first utilised in England during the 1890s and proved to be a more efficient system of slowing and stopping vehicles than the drum brake system. At that time, however, road conditions were not kind to this invention, and so it would be another fifty years before the disc brake system would be a more widely used invention.
Various Types of Brake Discs
Cast iron is the most common material composing brake discs, although some specialised brakes are constructed from composites such as reinforced carbon-carbon or ceramic matrix composites. While solid material is most typical, there are a few exceptions. Discs may have fins or even slots, particularly when used for racing vehicles. This chart illustrates the different design types, including ventilated, slotted, and cross-drilled discs, along with their intended uses.
Ventilated disc using fins or vanes
Vanes or fins are attached to both of the discs' contact surfaces during casting. The resulting ventilation allows the heat that is generated to dissipate more quickly.
Holes drilled through the surface of the brake disc aid heat dissipation. These are not used with racing vehicles, as small cracks can occur in the weakened surface.
Small channels in the disc encourage the removal of gas and dust. Used mainly in racing as this practice also wears the brake pads quickly.
Discs mounted half-loosely with coarse splines
Allows the disc to expand evenly and limits the damage that is possible from heat.
In addition to these specific types of design, composite brake discs are a specialised type of disc for use in a number of high-performance or heavy-duty vehicles. The first ceramic brakes were developed for the railway industry in Britain in 1988, with the goal of creating a brake disc that reduced weight as well as the number of brakes per axle, all while keeping the level of friction stable at high speeds and a variety of temperatures. The resulting technology, a carbon fibre-reinforced ceramic process, now has many uses in railway, aircraft, and automotive brakes. Ceramic composite brake discs are too cost-prohibitive for everyday vehicles, but for those higher-end sports cars where manufacturing costs are not an issue, the strength and heat tolerance of ceramic brakes make them an attractive choice. These brakes can withstand temperatures that would cause steel brakes to bend.
Porsche's own ceramic composite brakes are both vented and cross-drilled, with a lighter weight that lowers the brake weight by half, causing a significant overall drop in vehicle weight. They do not rust, there is a lower amount of dust, and their ceramic brake discs allow for more time in between maintenance and replacement. These ceramic brake pads are an optional feature for all Porsche vehicles and come standard on the higher-end models of the brand.
Types of Brake Disc Damage
There are four main types of damage in brake discs: scarring, cracking, warping, and rusting. Brake discs that have sustained such damage generally require either repaired or replaced. While there are ways in which one can repair, rather than replace, brake discs, often the cost of repairing the brake disc is close enough to the price of replacing with new brake discs that replacement is the logical choice.
If completely worn brake pads are not changed, then either the pads' steel backing in the case of glued pads, or the pads' retainer rivets in the case of riveted pads, come in contact with the disc's surface. This reduces the brakes' power and creates scratches in the surface of the brake disc. While very slight scarring may be acceptable, and replacing the brake pads alone are sufficient action, the presence of deeper scars means one must replace the discs as well.
Cracking is a form of damage usually limited to drilled discs. Because heating and cooling may cause the discs to expand and contract unevenly, small cracks may form near the drilled holes. It is not possible to repair these cracks; the discs should be replaced to avoid brake failure.
Incorrect fitting of the brake discs results in warping, meaning the change of a consistent shape which would cause lowered performance. While the warping of discs may occur, typically the discs that are diagnosed as warped are actually uneven due to the brake pads. If the material of the brake pad is unevenly transferred, the thickness of the brake disc becomes uneven.
Because discs are often made from cast iron, a certain level of rust is to be expected. Since the brake pads are in constant contact with the brake discs of a frequently used vehicle, surface rust is usually worn away. If, however, a vehicle is stored unused for an extended period of time, that rust may build up. Additionally, if the brake discs are ventilated, rust corrosion may get into the ventilation slots, which weakens the brake disc and causes the need for replacement.
Fortunately, it is simple to purchasing brake discs when one shops on eBay, an online auction site with a large inventory of many items, including those that fit automotive needs.
How to Buy Brake Discs on eBay
To find and purchase brake discs on eBay, type brake disc in the search bar. When the search results return, there are several ways to further restrict the search results to a more manageable number. One is to select from any of the suggested searches that appear. If you are looking for brake discs for Opel, for example, you can click on the hyperlink given. Another approach is to add your own keywords to the initial search if too many results are shown. Adding the word Ford, for example, refines the results to include only those brake discs that fit a Ford vehicle. Lastly, you may choose to limit the results by selecting from the provided subcategories, as well as choosing restrictions from the other categories, such as the condition of the brake pads or price limitations.
Once you have decided upon a particular listing or narrowed the possibilities down to a few listings, take the time to read the details carefully. If photos are provided, compare them to the written details. Pay strict attention to the measurements and any compatibility requirements, as they vary from vehicle to vehicle. Clicking on the name of each individual seller takes you to their eBay feedback page, where you can read comments left by past buyers as well as contact the seller securely without the need to reveal a personal email address.
Acquiring some background knowledge is essential when making any purchase, and brake discs are no exception. Before purchasing brake discs on eBay, it is important that the purchaser first take the time to learn about the purpose and use of brake discs. Learning about how brake pads work in a vehicle, the various types of damage that necessitate repair or replacement, and the different types of brake discs available educates the vehicle owner, enabling him or her to choose wisely. Whether one is in need of new brake discs for a classic car, or a modern sedan, or a race car, eBay has a wide selection of items to suit every car and owner.
Purchasing auto parts can be a daunting task for anyone, particularly for those with a limited knowledge of auto mechanics. Thus, some information as how to determine one's needs as well as how to purchase brake discs on eBay empowers the vehicle owner to make the right purchase. In no time, the vehicle owner can enjoy the experience of purchasing successfully on eBay.