While there is a difference between brake pads and shoes, the desired result is always the same when the foot goes down on the brake pedal. Brake pads clamp down onto a rotating disc. Brake shoes push out Flintstones-style onto a rotating drum. Inertia gets turned into heat via the miracle of friction. If all goes well things slow down. Each time the brake pads clamp themselves onto the rotor to put on the whoa, a small amount of the pad itself turns to dust. A smaller amount of the brake rotor also turns to dust. Brake pads are by design supposed to wear out, and for obvious reasons should be inspected and replaced once in a while. Read on for a brake pad bonanza.
Pad Swapping
While swapping in a new set of pads in place of worn out old ones seems a pretty simple, it is a task to best taken very seriously. There is zero room for short cuts or monkeying around when working on brakes. A service manual is crucial. A misstep made or shortcut taken during brake assembly could have dire circumstances. The exact procedure for getting to and replacing the brake pads is as varied as the many different kinds of cars in the world. If the brake pad swap is not completely obvious, then peer into the manual to solve any mysteries. Always check the condition of the brake rotor before installing new pads. If the rotor isn't excessively scored and still measures above minimum thickness then all is well. Swap out the old brake pads for new. If the rotor is too thin or full of peaks and valleys, then replace or resurface the rotor first. Brakes are not a place to skimp or save money.
Friction Materials Convention
The next choice to be made in a brake pad replacement is brake pad material itself. There is no one friction material that works best in every situation. Brake pad material designed for everyday mototring will quickly overheat during performance driving, causing rapid wear and brake fade. Super high-performance or racing brake pad material will never get hot enough to create braking friction in everyday driving. Running with race-compound brake pads on the street will just make a lot of noise, and can actually be dangerous. A general rule is the more aggressive the brake pad material, the faster the rotor will wear out. More noise should also be expected as friction material ratchets up the performance scale.
Extra Crispy
Selecting the right brake pad material starts with honesty. If driving down to the corner store for snacks is the routine, than super-performance brake pads are not required. If track days or canyon runs are marked out on the calendar, then a performance compounds may hold the answer. Organic pad material features normal stopping power and wear along with low or zero noise. Next up in line are the metallic or semi-metallic pads. Genuine metal makes these pads more aggressive, but can bring more noise and disc wear along to the brake party. Semi-metallic pads can be considered an upgrade over organics. Ceramic compounds allegedly offer the best of both worlds, with superior stopping power and long wear along with low or no noise. Another bonus to ceramics is lower dusting, which can keep those fancy wheels cleaner longer. Similar to tire compounds, brake pad friction material is about compromise. There is no free lunch.
Make Your Bed and Stop in It
Like a new set of Chuck Taylors a new set brake pads should be broken in for best results. One method is to drive around and make 8-10 full stops at moderate speeds followed by a cool-down period. Select a boulevard with a good amount of stoplights but not a ton of traffic. After the eight or tenth stop, park the vehicle and allow the brakes to cool for around 20 minutes. Don't set the parking brake! Go grab a burger, or coney island. Repeat the procedure on the way back to home base. The stopping and starting will heat cycle the material in the pads. Bed-in recommendations vary by manufacturer. Super performance pads may require specific bed-in procedures unique to pad material. While not entirely necessary with some compounds, running a bed-in is a good way to make sure everything was put back in the right way.
Stuff You'll Need:
· Service Manual
· Jack and Jack Stands
· Brake Pads
· Brake Parts Cleaner, and lots of it
· Catch Tray
· Gloves and Safety Goggles
· Hand Tools
· Torque Wrench
· Brake Caliper Tool(s)
· Brake Caliper Grease
· Brake Fluid
Jack up the old heap and remove the wheels. Use brake cleaner to remove brake dust and road grime. Do not use compressed air. Do not breathe brake dust. Handy tip for those inclined to immediately tear everything apart. Leave one side assembled for reference. Forgetting how the various anti-rattle clips, shims, and gizmos go back together is wicked easy to do.
New brake pads should never be installed onto excessively worn rotors or into spent and corroded brake calipers. Measure the rotor minimum thickness with an outside micrometer. The cheap plastic ones work fine for brake rotors. If the rotor is too thin it will overheat and warp. It may already have. Check rotor run-out (warping) with a dial gauge. Replace rotor if numbers don't mesh with those in the manual, or the minimum thickness stamped onto the rotor.
Get the hammer if you find one of these holding on the rotor and acting the goat. A smack or two on the screwdriver may be enough to loosen it. Still stubborn? Use an impact screwdriver. Penetrating or rust busting oil may also play a role.
If caliper removal is required to replace the pads, never let the caliper hang by the brake hose. Use a length of bailing wire or rest the caliper somewhere that causes no stress on the brake hose. Remove old pads and note position of clips, shims, and tabs.
These old pads still had some meat on 'em but were glazed. Delicious and sugary glaze is great on donuts, but lousy for brake pads. Glazed brake pads suffer a loss in efficiency as they lose their ability to bite into the rotor and create friction.
Remove the brake fluid reservoir cap, and some of the brake fluid. As the brake pads wear they become thinner, and the brake caliper piston pushes outward. The space behind the caliper fills up with brake fluid. See the reason why some brake fluid needs to be removed in the next step. Danger! Brake fluid will destroy painted finishes.
To install the new and thicker pads onto the rotor, the caliper piston may need to be compressed back into the caliper with one of these fancy tools. This action will push brake fluid back up into the reservoir. Auto parts stores will rent you a box-o-brake tools on the cheap. An old brake pad or two, a screwdriver, and some leverage is another method. Clean off the caliper piston first, as not to send dirt back into the caliper. Brake cleaner!
These calipers had been on the car for a few presidents and needed some fresh grease on the caliper slider pins. If the manual calls for grease, use only high-temperature grease designed specifically for brakes. Regular grease will melt all over everything. Brakes get wicked hot. Glazing is for donuts.
Install new pads into caliper making sure all shims, anti-rattle clips, tabs, and gee-gaws are in the right place. Use brake cleaner to remove any greasy fingerprints and other contaminants from pad surfaces and rotor before mounting caliper on disc.
Mount caliper back on the on disc. Use a torque wrench to torque mounting bolts to specifications. Clean one last time with brake cleaner just for kicks. Depress brake pedal to seat caliper piston and pads. Spin the disc to make sure it spins. Check and add brake fluid if needed. Finish up the other side or other three, and then bleed the brakes.
Related:
Bleed the Brakes; And You Will Know Us by the Trail of Parts [Internal]