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Summary
  • Power brakes use brake boosters to take the force you apply to your brake pedal and amplify it as force is transferred to the brake master cylinder.
  • The three types of power brakes are vacuum, hydraulic, and electric. Power brake conversion is the process of converting a vehicle’s manual brakes into power brakes.
  • When looking into power brake conversion, it’s important to consider whether it’s worth the effort without overhauling other parts of the braking system. You should also assess the parts availability and installation difficulties.

Power brakes are an amazing innovation and a vast improvement to the manual brakes on older vehicles. That doesn’t mean that classic vehicles are entirely left out, however. If you’re looking to improve your classic vehicle’s brake performance, shorten its stopping distance, and make braking easier on you as a driver, perhaps it’s time to look into power brake conversion.

What Are Power Brakes?

Power brakes use brake boosters to take the force you apply to your brake pedal and amplify it as it’s transferred to the brake master cylinder. From there, the rest of the brake system engages as normal. Power brakes significantly reduce the amount of force you need to place on the brake pedal when braking. There are three types of power brake boosters—vacuum, hydraulic, and electric, and they each amplify the force placed on the brake pedals in different ways.

Vacuum

Vacuum assist brakes are the original power brakes. These power brakes use a vacuum assist chamber near the brake pedal. The inside of the chamber is split into two sections with a moving metal plate between them. One section has a vacuum at all times created by the intake manifold. Depending on the brake pedal position, the second section is either at atmospheric pressure or has a vacuum.

A hole on the metal plate and a series of seals controls the amount of vacuum in the second section. When the brake pedal isn’t depressed, the seals remain closed and the vacuum in the first section creates a vacuum in the second section through the hole in the metal plate.

As the driver depresses the brake pedal, the seals simultaneously open to allow air into the section and seal off the hole in the metal plate. This creates a tremendous amount of force on the metal plate as air rushes into the vacuum of the second section. As the force pushes the metal plate, it in turn pushes on the brake master cylinder, which converts the force into hydraulic pressure on the brake fluid. The whole process makes engaging the brakes much easier.

Hydraulic

Hydraulic brake boosters operate similarly to vacuum assist brakes in that they increase the amount of pressure placed on the brake master cylinder whenever the driver hits the brakes. However, instead of using vacuum from the intake manifold, hydraulic power brakes use the hydraulic pressure from the power steering column.

Electric

Electric power brakes are another type of brake boosters. These brake boosters use an electric pump and a booster system to create extra pressure on the brake master cylinder whenever the driver depresses the brake pedal. These power brakes are especially helpful for engines with low vacuum.

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What Is Power Brake Conversion?

Power brake conversion is the process of converting a vehicle’s manual brakes into power brakes. It’s a popular procedure for classic vehicles, and it’s often done in tandem with other brake system improvements like converting drum brakes to disc brakes. Power brake conversion improves braking systems by making them easier to operate and improving stopping distance.

Power Brake Conversion Tips

Power brake conversion isn’t a procedure to be taken lightly. You need mechanic-level experience to safely execute the installation. If you plan on converting your manual brakes into power brakes, here are some handy tips.

Considerations

There are a couple of things to keep in mind when deciding whether to proceed with power brake conversion. For instance, installing a power brake booster will definitely help you increase pressure when stepping on the brakes, but if you don’t improve the brakes on the wheels themselves, it makes less of an impact on your vehicle’s braking efficiency.

Consider what type of power brakes you’ll need to install as well. If your engine doesn’t create enough vacuum pressure, you’ll need to use either a hydraulic or electric power brake system instead.

Also, you’ll need to account for pedal ratio when installing power brakes. Manual brake vehicles have a pedal ratio of 6:1, while power brake vehicles have a pedal ratio of 4:1. Pedal ratio has to do with the brake pedal’s pivot point and its distance from the middle of the footpad. As the first number in the ratio goes up, the brake force placed on the master cylinder also increases without the need for extra pressure on the pedal. However, it also necessitates more pedal travel when attempting to engage the brakes.

Parts and Kits

Power brake conversion kits come with most of the parts you need for the installation. Specialized kits are also available for specific vehicles. These kits are often the best fit for those vehicles, with calculations on pedal ratios and the like already accounted for. Power brake conversion kits will likely include a new brake pedal to address the reduced pedal ratio, brake fluid reservoirs, a proportioning valve to split the braking force between the front and rear wheels, and a brake force distribution block.

If you’re looking to create your own power brake kit for a vehicle without a pre-existing kit, then you’ll likely need to fabricate your own mounting points and bend new brake lines.

Installation

Installing your power brake conversion kit will take a good amount of time and effort. Remember to leave this step to a trusted mechanic if you aren’t too familiar with the braking system. You’ll often need to remove numerous parts before you can even begin. Access to the master cylinder is essential, and in a packed engine bay, it’ll take a lot of finagling. Don’t forget to disconnect the brake lines as well.

After that, it’s a matter of removing the old master cylinder and the brake pads. Once you install the new master cylinder, vacuum hose, brake pedal, and brake booster, you can reattach the brake lines and bleed the system to start completely fresh.

Modern vehicles all benefit from power brakes, and while installing one in your vintage car might take a good amount of time, effort, and money, it’s definitely worth it if you’re upgrading the entire system. Now that you know about what goes into power brake conversion, you can decide whether it’s worth doing.

About The Author
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

File Under : Braking System , DIY
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