Jim Smart
August 7, 2007

Drum Brakes Done Right
Likely the biggest problems behind drum-brake performance issues are inattention to detail and being a cheapskate about your brakes. Drum brakes are high maintenance and temperamental. They demand the best components and your closest attention. Whenever you rebuild drum brakes, start clean with new, high-quality components, including springs and hardware, riveted linings, wheel cylinders, and new or resurfaced drums.

Stainless Steel Brakes makes a Kelsey-Hayes-design four-piston, front-disc brake kit for classic Mustangs and other Ford compacts and intermediates. They can be installed on any V-8 drum-brake spindle.

When you go cheap with used components, you're asking for trouble. Drum-brake components last for one, maybe two brake jobs. Springs lose their tension. Hard parts wear out. Wheel cylinders develop leaks. Drums become too large internally. Drums should be machine turned by qualified personnel at every brake job and replaced at every other relining. Even though inside drum dimensions are within limits, drum brakes perform their best when shoes travel the shortest distance.

The bottom line with drum brakes is this-never cut corners. Use the best components, riveted linings, and new drums when it's time for an overhaul. When you don't turn drums, shoes can't bed like they need to. Whenever you push drums to their legal limit, brakes will not perform their best. They will also make unwanted noise because the shoe itself will rub the drum, causing an annoying squeal. Remember: one turning to a drum, then toss it.

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This exploded view of a '65-'66 Mustang power-brake booster shows the diaphragm, return spring, bellows, and more. When you touch the brake pedal, intake-manifold vacuum takes over and assists braking effort.

What Are Power Brakes?
There are two basic types of power-brake systems-vacuum assist and hydroboost. Vacuum assist is most common, employing a chamber divided by a spring-loaded diaphragm. The engine's intake-manifold vacuum creates negative pressure (suction) on one side-the side nearest the master cylinder. The diaphragm is drawn toward negative pressure, which helps the driver apply pressure to the master cylinder's piston rod. Intake manifold vacuum helps the driver do the braking, easing pedal effort.

Hydroboost power brakes work like power steering. When you touch the brake pedal, you open a control valve that applies pressure to the master cylinder, easing pedal effort. Hydroboost isn't at the mercy of faltering intake-manifold vacuum when you have a hot cam. As long as the engine is running, hydroboost gives you power-brake assistance. Hydroboost pressure comes off the power-steering pump-even if your Ford doesn't have power steering.

Hydroboost power-brake units can be sourced a variety of places, including Power Brake Service [www.powerbrakesonline.com, (800) 504-1060] and Hydratech Braking Systems [www.hydratechbraking.com, (586) 427-6970]. Hoses can be fabricated at a hydraulic or air-conditioning shop. Mustangs from 1996 to 2004 with SOHC and DOHC V-8s have hydroboost power brakes. So did some Lincolns and Mercurys. These are good sources for the units if you decide to fabricate your own setup. If you can't find one in a salvage yard, order one from your favorite auto-parts store, and be prepared to pay the core charge.

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Brake- Bleeding Technique
Through the years, we have seen a lot of different approaches to brake bleeding. Most of us subscribe to the shade-tree approach of having a buddy work the pedal while we work the bleeders.

There are also tools that enable you to bleed brakes by yourself. One is a pneumatic-pressure bleeder that places air pressure on top of the master cylinder's brake fluid, pushing fluid and air out through bleeders. Another tool uses a hand-pump method, pushing fluid and air back through the master cylinder. Both systems are quite affordable.