Mustang Club of Maryland

Replacing Disc Brake Pads
Created by Tom Morr

Poll most professional drivers/racers about a car's most important system and many will vote for brakes without hesitation (so to speak). Steering is also toward the top of the list, but without good brakes, driving at speed can be a kamikaze mission waiting to happen.

New Linings

Disc-brake systems are much more user-friendly than comparatively Neanderthal drum setups. Because their components aren't obscured by a brake drum, disc systems are easier to inspect and access. The average home mechanic can easily replace disc pads, although other problems such as fluid leaks and rotor surface irregularities are often better left for a pro.

Brake Check

Signs of brake problems include:

> The car pulling to one side during braking.

> Squeaks, grinding or other noises when the brakes are applied.

> The pedal goes farther toward the floor than normal.

> The pedal pulsates during regular (non-panic) braking.

> Evidence of brake fluid inside the tire/wheel or on the ground.

The brakes should be visually inspected every time the car's wheels are off for tire rotation or other service. When working with brakes, always err on the side of caution by wearing a filtering mask—brake dust might contain asbestos.

Pads can usually be inspected through the opening in the caliper body. If the lining thickness is approximately 1/8 inch or less, the pads should be replaced. Alternately, most pad pairs have a wear sensor. This is a little metal tab that rubs against the rotor and makes a squealing sound when the pad has little lining left.

In addition to pads, rotors should also be inspected. Look for obvious signs of wear, such as cracks, gouges or burned spots. Then run your fingers across the pad-contact area to feel for hills and valleys on the rotor's friction surface. Any irregularities are cause to resurface (assuming the rotor is thick enough) or replace the rotor. Many parts stores will resurface rotors for a nominal charge when purchasing brake pads. These retailers can also recommend the pad material/style that best suits your vehicle and driving style.

As part of the visual inspection, look for signs of brake fluid. Common locations of seepage are below the master cylinder, at brake-line fittings and in the caliper's piston(s)' boot area. Once the leak is diagnosed and corrected, the brakes usually need to be bled.

Installation Tips

> De-gunk parts with brake cleaner only; never use petroleum-based solvents.

> Siphon about half of the fluid from the master cylinder to make room for the back flow created by retracting the caliper pistons. Use a pump-style siphon (not your mouth) and dispose of the old fluid properly. (Never reuse brake fluid—it can absorb moisture and become contaminated when exposed to air.)

> Raise and secure the vehicle properly using jack stands, tire chocks and the vehicle's parking brake as necessary.

> Newer vehicles might have electrical connections for the antilock brake system that need to be disconnected in order to change the pads. Reconnect afterward.

> Calipers normally have to be removed from the vehicle to replace the pads. Removal procedure depends on whether the calipers are fixed or movable. Either way, each caliper typically is secured with two bolts. Verify that you have the proper tool (sometimes an Allen wrench or even a large Torx bit) before disassembling the vehicle.

> Caliper pistons usually need to be retracted so that the new pads (which have thicker linings than the worn ones) will fit over the rotors. Special tools are designed specifically for this purpose, although using a C-clamp between the old inboard pad and exterior of the caliper body will often work.

> After the caliper is removed, secure it to the vehicle with wire or even a bungee cord so that the rubber hose won't have to support the caliper's weight.

> Clean the disassembled components with brake cleaner and a wire brush as necessary to remove brake dust and debris.

> Pad attachment methods vary. Some clip into the piston itself, others to the caliper body, some have their own mounting brackets and others even have tabs that need to be bent over the caliper.

> On some vehicles that have movable calipers, the mounting pins/bolts aren't intended to be reused. Lube the movable parts of the new pins/bolts with high-temp grease. If the caliper moves on the steering knuckle, lubricate the contact areas as well.

> Keep grease, oil, and other lubricants off of the pad and rotor surfaces. Douse thoroughly with brake cleaner if in doubt.

> Read the instructions included with the new pads and refer to a service manual for your vehicle for fastener torque specs and any specific requirements.

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