【龍Sir教室 Ep24】關於煞車的十五問（內附字幕）｜TopGear HK 極速誌 topgearhk

Before shooting In the Facebook Driver's Club group Ask everyone about the brakes The response was very enthusiastic This time I try my best to answer If you feel braking is not responsive First ask yourself Does it feel like stepping on sponge if so That is, there are bubbles in the brake system If you step on the brake After passing the normal position Normal reaction force Normally can brake linearly But now it takes more force to apply the brakes to be effective The brake pads and brake discs are alright I think I need to upgrade the brakes The truth is that the brake discs are often stained Especially oil stains The car repairer often has oil on his hands If you have touched the brake disc To evaporate this oil stain The temperature is often two or three degrees Celsius If you drive very gracefully The brake temperature is often over a hundred degrees Can't evaporate the oil on the dish all the way Makes you think that the braking performance is insufficient Actually it's okay Buy brake cleaner About fifty dollars Disc brake pads Spray wash all those parts It's fine now If it feels soft like sponge when you step on the brake That means there are bubbles in the brake system Must find a repairer to exhaust the air Usually two possible reasons First, the brake disc is deformed The second is the anti-lock braking system (ABS) being activated How to distinguish? If it is ABS You will hear the sound of "Da Da Da" when the ABS is activated If the disc is deformed No sound Only the pedal rebounds The brake discs must be replaced If ABS is activated for no reason It may be that the sensor is dirty Or it's broken and need to be replaced European cars usually use softer brake pads Can increase the friction coefficient The disadvantage is that the brake pads and brake discs wear faster In exchange for Is a faster and quieter braking response Drive a European car There is this trade-off There are two types of rust One is where the brake pads rub against Where the performance is brighter This part is harder to rust The rest of the brake disc Because there is no friction Easier to rust Where there is friction Be polished Smaller surface area Slower oxidation rate But I haven't started it for a few days Or get water Will still rust The cast iron will have rust Don't worry too much When you drive again Brake slightly Will remove the rust stains on the surface Really pay attention The car only drove for a while before the car was washed Or just finished the mountain road The temperature of the brake system is very different If the temperature is high Wash the brake system with plenty of water May cause deformation of brake disc Especially new cars New cast brake disc A little internal stress during manufacturing With the use of the car for a while And these internal stresses slowly release When the disc is still very new Large internal stress Give it this kind of thermal shock Chance to cause deformation Really be careful In this way Can a new car not drive on a rainy day? Is not The amount of rain or raindrops Far inferior to direct spraying with a hose Many people think whether the brake pads should be changed You know when you step on the brake The truth is not like this If it is a four-wheel disc brake Worn out brake pads The driver will not know if he brakes No feeling Drums are different There is also an automatic gap adjustment function in the drum brake But this function is not a stepless operation Between each interval There will be gaps When there is a gap You can feel the depth of the pedal when you step on it After finishing the gap, I was held up And then step on that is the force of the brake So a four-wheel disc brake car The driver does not know How to check The most correct way is to remove the wheel Check the thickness of the brake pads The lazier way is to visually check from the outside This is not so good Floating calipers will fail Floating force blocked The sub-cylinder pushes the brake pads behind the disc Sometimes the pad inside wears out more But pad on the outside is fine In fact inside one has been worn away So it’s best to remove the wheel If the brake pads are severely worn Open the hood Check the brake fluid level drop Someone sees the brake fluid drops and adds This approach is wrong Sensor in the brake fluid storage tank When the level is low There will be warning lights If you add brake fluid Misled yourself Until the brake pads are completely worn out You don't know The brake pads also have a reminder function It contains a piece of copper After a certain degree of worn out The copper plate rubs against the brake disc Will make a sharp ear sound The brake pad is thin But not all brake pads have this design The best way is to disassemble the wheel to check Brake pads and discs Work through friction So the brake disc will also be worn When the disc body appears pitting Or sunken Someone will polish the brake disc This is how it was done decades ago Today if the cost of polishing brake disc Chances are more expensive than buying a new disc So there should not be too many people in Hong Kong to do so How long can the brake disc last We should use a set of brake discs How many sets of brake pads can be used to calculate Every car is different Some car manufacturers use softer brake pads You can change the brake pads two or three times The brake discs are still in good condition The brake is the most important safety system of a car Everyone must find a reliable repairer Regular inspection Which parts need to be replaced Brake fluid is a very stable substance But it has a disadvantage Is that it has a strong affinity for water Easily absorbs water When the brake fluid has moisture Even if it's only 2 or 3% The original boiling point drops Because the boiling point of water is 100 degrees Bubbles when boiling Will disable the brakes Check the brake fluid Is to check for moisture There used to be many methods such as test paper Now put in the brake fluid with electronic equipment Know if there is any water simply put Change the brake fluid every three or four years The size of the brake disc Depends on the workload of the brake system How big is the workload Depends on how heavy the wheel load is when braking The front wheel driven car Even at rest The front axle has a heavier load than the rear axle The center of gravity moves forward when braking More front wheel load So the front brake needs to be larger More than just the front wheels driven car As long as the front is heavier than the rear Or the body's center of gravity is high The center of gravity moves forward when braking The front brakes are bigger than the rear Simple junior high school physics class Strength is like pressure times area Braking action from the brake server and the driver Pressure is so much How powerful It depends on the area If the caliper is large, the area is large Power is stronger If the piston distribution can use up the caliper area Power is stronger simply put The bigger the caliper, the more pistons The braking force will be greater Another interesting question Same size of caliper Some are four pistons Some are six pistons Which is better Why put six pistons The purpose is to use up the space of the caliper Put four big pistons With six small pistons Look at the remaining space in the caliper that is not covered by the piston Which is more Certainly six small pistons can use up more space Will get a larger working area Greater braking force We talked about brake failure There will be gasification The gas coming out is caught in Between the brake disc and the brake pad The brakes fail Pit pattern and drilling disc The purpose is to exhaust the gas Can delay the threshold point of failure The advantage of high-performance brake pads is high temperature resistance But it needs to have a certain working temperature Ordinary brake pads Regardless of low temperature or high temperature Performance is similar It reacts when you step on the brake High performance brake pads When the temperature is low Poor friction coefficient After the temperature rises Performance gets better At extremely high temperatures Work performance is better than ordinary brake pads If driving is not aggressive The brakes are not often at extremely high temperatures Use high-performance brake pads May get opposite effect If you think the original brake system is not strong enough Want to upgrade Of course the overall replacement is better Larger calipers Better brake pads Better brake discs If you only change the brake discs or brake pads what's going to happen Use original brake pads But with upgraded brake discs At the critical point of thermal failure Because the upgrade disc has holes or pits Can exhaust Can delay the critical point of thermal failure If you don’t change the brake disc Only put on higher performance brake pads When reaching the working temperature The coefficient of friction will be higher The problem is that the brake discs may not be able to withstand Such high-performance brake pads Wear faster Meaning of floating dish Central part of brake disc The ordinary dish is made entirely The floating dish is the two parts The advantage is that lighter materials can be used in the central part Such as aluminum alloy And ordinary brake discs are different due to heat There is a chance of large temperature difference and deformation Some special brake discs such as ceramic Because you can't make complex shapes So it is divided into two parts for manufacturing and then assembling Also, the disc and the central part are in elastic contact When the brake pads are pressed down Can find the contact point of the disc faster and easier The braking response will be faster It really depends on who drives the bus If I drive it, it will be fine Because I know the principle of bus braking The automatic gearboxes of Hong Kong double-decker bus Come from ZF or Voith There is a hydraulic retarder in the gearbox The bus driver should know this hydraulic retarder If you know how to use Lightly brake The brake pads are not working First activate the retarder Everyone will hear the voice of "Vee" The speed of the car will slow down evenly Brake a little deeper The brake system works Slow down further If you can make good use of these two levels of deceleration, Get a very average deceleration effect The brakes are not easy to overheat

Channel: TopGear HK 極速誌

Views: 118,067

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Id: ovFpXQ9fG1Q

Length: 14min 39sec (879 seconds)

Published: Tue Dec 29 2020