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2023

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Why do you have to step on the brakes twice before driving after changing the brake pads?

Source:

Wondee Autoparts


Many people replace their own brake pads. In addition to ensuring that the brake pads are installed correctly and not reversed, the most important operation after replacing the brake pads is to step on the brake pedal in place. This operation is often forgotten, even in 4S stores or repair shops, sometimes after replacing the brake pads.

Many people replace their own brake pads. In addition to ensuring that the brake pads are installed correctly and not reversed, the most important operation after replacing the brake pads is to step on the brake pedal in place. This operation is often forgotten, even in 4S stores or repair shops, sometimes after replacing the brake pads. If you don't press the brake and drive away directly, the ultimate consequence is basically a collision, because the brake pads have just been replaced and the first two feet are not braked. When driving at low speeds, it is usually very close to obstacles before stepping on the brake. Stepping on the brake pedal feels light and there is no braking. Most people panic and won't step on it continuously, ultimately leading to accidents. This is a reminder that all car owners who change brake pads should take it seriously.

       changing the brake pads (1)

Why do the first two feet not brake after changing the brake pads? The fundamental reason is that the brake pads are too far away from the brake discs. Stepping on the brake pedal, although the brake pads also moved forward to clamp the brake disc, the distance they moved forward was not enough to make contact with the brake disc, and the two could not generate friction to brake. Why is the new brake pad too far away from the brake disc? This is necessary for installing brake pads, otherwise the new brake pads cannot be installed smoothly.

       changing the brake pads (2)

 

Under normal circumstances, the brake pads and brake discs are always close together, so that the piston moves outward a little to brake. As the brake pads become thinner, the piston of the slave cylinder will gradually move outward. The thickness of the new brake pads is very high. Before installation, it is necessary to fully push the piston of the brake cylinder back, that is, the piston is completely retracted into the cylinder, so that there is enough space to install the new brake pads. If the piston does not retract, the brake pads will be blocked by the piston during installation and cannot be installed. Due to the complete retraction of the piston, the distance between the piston and the brake disc is far. Even if thick new brake pads are installed, assuming that the new brake pads are close to the piston, it must not be able to touch the brake disc. The piston needs to move outward for a long distance to contact the brake disc against the brake pads.

       changing the brake pads (3)

It is precisely because the piston is completely retracted and the distance between the brake pads and the brake disc is far that the first two feet are not braked. When stepping on the brake, the master cylinder piston pushes the brake fluid forward, and the brake fluid then pushes the slave cylinder piston forward. When the first brake is applied, the distance for the master cylinder and the slave cylinder to move forward is not long. Although the cylinder piston has moved outward, due to its long distance from the brake disc, it cannot reach the brake disc even after one movement. You need to release the brake and press it again, then move a little further outward to reach the brake disc. As long as the piston is pressed against the brake pads and the brake disc are tightly against each other, the brakes can resume normal operation. So generally, it is necessary to press the brake pedal twice to allow the cylinder piston to move outward twice.

       changing the brake pads (4)

  Don't forget to step on the brake when replacing the brake pads yourself. When replacing the brake pads at a 4S store or repair shop, a repair technician usually helps to step on them. However, if you are on site, after replacing them, you will be asked to drive the car directly out of the workshop, and the repair technician may also forget to step on them. At this time, don't forget to step on them yourself. At any time, if you feel that the brakes are not working, never give up on the brakes, it's best to keep pressing them continuously. At low speeds, the handbrake is the best brake assist component. If you don't have the brake, you can still consider using the handbrake. Don't forget.

From: WONDEE Autoparts 2023-12-26

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