Do You Need To Replace The Master Cylinder?
If you are doing a disc brake conversion on a pre-1970s vehicle, you may need to replace the master cylinder. If you do need a new master cylinder, you can replace it before or after you perform your disc brake conversion. To do this, you will need a master cylinder, booster, vacuum hose and proportioning valve. These parts are frequently sold as kits. [source: Cook]
Front Disc Brake Conversion
If you're doing a front disc brake conversion, you're probably working on an older vehicle. This may mean that you will have to do more than simply replace the old brakes.
Removing the Drum Brakes
Not all drum brakes are created equal, but they're all similar enough that removing them follows the same basic steps. Start by removing the wheels and tires. Next, you will need to take off the dust cap, and then remove the center nut, washer and brake-drum bolts.
Disconnect the brake hose before you remove the drum, and once you've taken the drum off, you should inspect the spindle. If the spindle is worn or rusted, you should replace it. But if it looks good, you can clean it up and reuse it. Now just reposition and secure the steering arm and you're halfway to the finish line.
Installing the Disc Brakes
Some brake conversion kits come pre-assembled, but assuming yours isn't, or if you're using recycled parts, here's how you can assemble your disc brakes. Attach the rotor to the spindle and then put on the bearing and nut, the washer and the cotter pin. Now put on the dust cap, and then you can move on to the caliper assembly.
Before you put the caliper on the rotor, attach the new brake lines and install the pads. Then you can put the caliper in position over the rotor, reattach the brake lines and then back go the wheels and tires.
After you've finished the conversion, you will need to bleed the brakes and refresh the brake fluid. Bleeding the brakes will flush out any air that's gotten into the brake line. And since you've disconnected those lines, there will be air inside. This can cause your brakes to feel spongy or can make your pedal dip close to the floor.
Let's move on to how to do a successful rear disc conversion.
