[YesAuto Technology] As the saying goes, “It's easy to run fast, but it's hard to stop.” When we look at the parameter configuration table of the vehicle, we are often attracted by engine parameters, comfort equipment or space size, and often ignore the relevant information of the brake system, tires, and spare tires in the vehicle's “bottom plate”. What is the disc brake indicated on the colorful configuration table? What is the carbon fiber ceramic brake disc that can be used for a lot of money? How many inches are the tires of my car? What is the difference between a full-size spare tire and a non-full-size spare tire? In recent years, the development of new technology has brought “fresh blood” like EPB to the braking system. What is it? If you have any questions about these issues, let us walk into this issue of Interpreting the parameter configuration table article.
■ Why do we write “Interpretation of Parameter Configuration Table”
For a long time, whether it is a new model release or a 4S shop to select a vehicle, we will inevitably pay attention to various parameters. It is like a person's resume, which can show the basic information of the vehicle more comprehensively and clearly, but there are many knowledge points in these relatively boring data. Does the width of the body include rearview mirrors? Is the curb weight the same as the maximum design weight? Are ESP and EPS the same thing? These confusing things may appear on the parameter configuration table, so we decided to make a series of articles “Interpreting the parameter configuration table” to let you play with the configuration table and refuse to “fudge”.
|“Interpretation of Parameter Configuration Table” series of articles|
|Phase one||Body parameters|
|the second term||Engine parameters|
|Third period||Gearbox parameters|
|Fourth period||Suspension part|
|Fifth period||Motor parameters|
|Sixth period||Power steering|
■ Front and rear brake types
In layman's terms, the brake is the brake we often talk about. From a functional point of view, its role is to hinder the advancement of the car, or the mechanism of the movement trend, it and the parking brake we will talk about later are two systems. At present, most of the common brakes on the market produce a braking effect through the friction between a fixed element and a working surface of a rotating element. It can be roughly divided into drum brakes and disc brakes.
● Drum brake
As one of the two most common brakes, drum brakes have a long history. This design was applied to some carriages in 1902, and after the 1920s, cars, which were still new things at the time, also began to be applied.
Drum brakes are usually composed of brake drums, brake shoes, and brake wheel cylinders that drive the brake shoes. The brake drum rotates with the wheel, and the brake shoe inside it moves under the push of the brake wheel cylinder and squeezes the inner surface of the brake drum, and the torque generated by friction prevents the wheel from rotating to achieve the purpose of braking.
It can be found from the above structural diagram that the drum brake shape is relatively closed. Therefore, after continuous and high-intensity braking, the internal heat accumulation is more obvious, and the heat attenuation phenomenon is more obvious than the disc brake that will be mentioned later. In addition, after a certain mileage in the later period, the need to deal with the brake powder produced by the friction of the brake shoe is also a disadvantage. When the brake drum is immersed in water, the impact of drum braking efficiency is also more obvious than that of the disc brakes discussed below.
Tips: What is thermal attenuation?
In layman's terms, all mechanical performance degradation caused by high temperature can be called thermal attenuation. For the braking system, the thermal decay phenomenon is that after continuous and high-intensity braking, the temperature of the brake drum, brake disc and other components exceeds the optimal braking effect area, which causes the braking effect to decline. Happening. Reflected in the actual driving experience is the gradual increase in the braking distance of the vehicle following continuous and high-intensity braking behavior.
● Disc brake
Unlike drum brakes, the rotating element of a disc brake is a brake disc, and the friction against it becomes a brake caliper. When the vehicle needs to brake, the brake caliper is pushed by hydraulic pressure, and the friction material (brake pad) on it clamps the rotating brake disc. This process is very similar to the braking process of our bicycle.
When the vehicle is braking, because the center of gravity moves forward, the load on the front wheel braking system is relatively large. At present, more and more vehicles choose brake discs for the front wheel brake system. After using disc brakes on the front wheels, the thermal attenuation is relatively low, which is also conducive to improving the braking stability of the entire vehicle.
With the development of technology, ventilated brake discs began to walk around us. As the name suggests, its interior is hollow, and its counterpart is a solid disk. The cold air of the ventilating pan can pass through the middle to cool down. From the outside, it has many holes on the circumference that lead to the center of the circle. The centrifugal force generated during the driving of the car can make the air convection, so as to achieve the purpose of heat dissipation. Therefore, it has a better heat dissipation effect than ordinary solid disc brakes, and the heat attenuation phenomenon is relatively weaker.
-Perforated ventilated pan type
Since it is possible to “ventilate” the brake disc, smart engineers must further think of a good way to cool the brake disc, and the perforated ventilation disc came into being. It is based on the ventilation plate to perforate the plate surface to ensure air circulation to the greatest extent and reduce heat attenuation.
Of course, perforating, scoring, and changing from a solid disk to a hollow disk on the brake disk all require a lot of industrial design, calculation, and experimentation. In the absence of the above technical support, the original intention of the car owner to perforate and scribe the brake disc to improve the heat dissipation capacity of the brake disc will often result in damage to the brake disc structure and weakened strength.
-Carbon fiber ceramic ventilated brake disc
For those supercars who are only fast but not broken, the excess weight on their bodies still keeps them awake at night. Like many technologies mentioned before, carbon fiber ceramic brake discs are also a kind of technology decentralization. It can be traced back to the 1970s, when it was first used in aerospace braking systems. After entering the 1980s, motorsports began to be used. Since then, supercars led by Ferrari ENZO have also begun to match.
However, although there is ceramics in the name, it is by no means the ceramics we see everyday. It is made of high-performance materials that are specially mixed with powder, resin and fiber through a complex manufacturing process. The weight of carbon fiber ceramic discs is less than half that of ordinary cast iron discs. For example, the SLR MCIAREB with ceramic brakes has a front wheel brake disc with a diameter of 370mm but weighs only 6.4 kg. The CL-CLASS, which uses ordinary brake discs, has a front disc diameter of 360mm but weighs up to 15.4 kg. In addition to the advantages of reducing weight, carbon fiber ceramic brake discs have better thermal attenuation resistance, which can better help them to “stand up” faster in terms of acceleration and extreme speed.
As mentioned earlier, carbon fiber ceramic brake discs are not a perfect thing. The expensive price is one of the reasons that hinder their popularity. On the other hand, before the carbon fiber ceramic brake disc reaches the working temperature, that is, when the temperature is low, Its braking effect is not ideal, and sometimes it will produce a slight abnormal noise.
■ Parking brake
When it comes to parking brakes, the first reaction of most people is probably the handbrake. In fact, with the increasing use of electronic equipment in recent years, the types of parking brakes have gradually enriched.
● Mechanical handbrake
When we are in the driving school, the coach will almost repeat the teaching of “parking and pulling the handbrake”. Its function is the parking brake as described in technical terms. Its use method no longer needs to be repeated here, as the most common type of parking brake, you can almost see it on most cars.
In addition to the handbrake placed between the driver's seat and the front passenger's seat, some models have auxiliary brakes placed near the accelerator and brake pedals. This is what we often call “foot brakes”. In principle, it is not much different from the mechanical handbrake, except that the layout is different. People who are not familiar with the position may forget to lift the vehicle after starting.
● Electronic parking brake
If you have ever gone to a 4S store to see a car, there will probably be salespeople who say that their products are equipped with EPB. Maybe they will also say that with this feature, you can sit back and relax in corners. In fact, EPB (Electrical Park Brake) stands for Electronic Park Brake.
EPB, or electronic handbrake, can integrate the functions of temporary braking during driving and long-term braking after parking. The parking brake is realized by electronic control. In many cases, EPB is confused with ESC, which has similar spellings. In fact, these are two systems with different functions. ESC is the body electronic stability program, which is a further extension of the ABS and traction control system TCS functions to ensure the stability of the vehicle. Therefore, EPB and ESC are two configurations, and their roles are completely different.
■ Front and rear tire specifications
When it comes to tires, we are all familiar with it. As the only part of the vehicle in contact with the road, in this small area, it not only has to bear the weight of the car body, but also filter out part of the vibration. Therefore, it is necessary for us to understand the parameters on the tire.
● Where to find the parameters
Similar to vehicle nameplates, tires also have their own “identification system.” However, the slight difference is that the tire’s identification system has more numbers and letters. First of all, let us first understand where this information is hidden?
● What are the parameters?
After knowing where the parameters are, you will find that there are as dense numbers on the sidewall as in high school mathematics textbooks. Simply put, it includes the tire manufacturer, the series, the size specifications, and the maximum allowable load quality. , The maximum allowable driving speed, installation direction, etc., let us look at the most important sets of parameters that are usually used in purchase and use.
The “55” in the 205/55 R16 group of numbers represents the aspect ratio, which refers to the ratio of the height from the rim to the tread to the maximum width of the tire section, expressed as a percentage, that is, the height occupies the width Percentage. In the case of a fixed tire width or crown, the smaller the flatness ratio means the thinner the tire wall, and the visual effect will appear to be larger. Of course, the thinner the tire wall means the weaker its ability to filter road vibrations.
The letter R in the above parameters also has its meaning. It represents that the tire is a radial tire, which means that the tire inner cord weave arrangement is at a 90-degree angle to the center line of the tread, which is named after the meridian on a globe. Generally, the crown part of this kind of tire will increase the steel wire layer, so that it can withstand greater internal pressure stress, has the characteristics of less deformation of the tread, better ground grip and stability, and is more suitable for high-speed driving. Therefore, nowadays cars generally use radial tires.
-Speed grade, load index
Having seen the tire specifications and size parameters, let us look at a set of parameters that are usually overlooked. Its height will directly affect the maximum weight that the tire can bear and the maximum speed allowed by the design.
|Load index comparison table|
|Numerical value||Allowable load index||Numerical value||Maximum allowable load index|
When we buy and use tires every day, we always talk about terms such as grip and wear resistance. In addition to word of mouth when choosing tires, is there a quantitative standard to help us choose tires scientifically and reasonably? The “3T” index can be used for your reference to a certain extent.
In addition, the traction index may be different in our usual understanding. It refers to the classification of the longitudinal traction coefficient obtained by the straight-line braking of the wet ground on a specific road, rather than the grip performance of all grounds that we understand in a broad sense. In other words, the better the index rating the tires will have better performance in straight braking, acceleration, and starting under rain and snow, but it will not affect the handling performance of the corners.
-Production date, wear indication
-Other important parameters
In addition to the parameters mentioned above, the tire manufacturer’s LOGO or the technology used by the tire will also appear on the sidewall of the tire. These details will change due to different manufacturers and technologies. In addition, the tires are also There are some signs that are also worthy of your attention.
■ Spare tire specifications
After reading the tire-related parameters, let us understand the spare tire part. Although it may only be squeezed in an inconspicuous corner on the common parameter configuration table, it will directly affect your use in an emergency.
Full text summary:
In this issue of the article, we mainly interpret the contents of the service brake, parking brake, and tires and spare tires. From a practical point of view, traditional drum brakes can already meet the demands of service braking in most situations. In order to compensate for the thermal attenuation caused by continuous and high-intensity braking, disc brakes have emerged. Of course, for luxury cars and supercars that don't care about cost, ventilated discs and carbon fiber ceramic brake discs have become their first choice. In the tire section, in addition to the specifications, the “3T” index, internal and external markings, and installation directions are also worthy of your attention.