Friction Materials: The brake pads, rotors, shoes, and drums used to slow down the spinning wheels on your car all fall into a category of parts called friction materials. They accomplish their work through the use of friction—and like any two materials that are rubbed against each other repeatedly (which is how you generate friction), they will wear or deteriorate over time. Friction materials are meant to be replaced, because wear and tear are inevitable results of their function. So don’t grumble about having to get them swapped out or unfairly place blame on your car or your mechanic.
Made of metal, rotors are a lot more durable than brake pad material, so they don’t wear away as fast. But if you wait too long to replace your brake pads, all the friction material on the pads will wear away. You will have a metal (brake-pad backing) on metal (rotor) situation that results in a grinding sound and a wearing-down of the expensive rotor. The surface of the metal rotor will be scored with scratches, deep grooves, and general roughness.
When brake pads wear down to 2–3 mms, it’s time to have them replaced.
The Miracle of ABS
Given everything that’s going on when you press on the brake pedal, it’s no wonder brake systems are loaded up with a slew of computers and sensors. There are switches that illuminate your rear brake lights, sensors that monitor brake fluid level, and valves that ensure boosted force is evenly distributed to each wheel.
Some of these sensors are designed to override our instincts. We tend to slam on our brakes when we’re faced with close calls, for instance—if we’re trying to avoid a crash, if the car begins to slide, or if we lose control due to poor traction between our tires and a wet or icy road. But slamming down on that pedal as you skid out of control only makes matters worse. When you panic-brake, you overtax the valves that monitor boosted force and spread that force evenly to the wheels. And if one or more of the wheels experiences a surplus of force, the brake pads and caliper clamp down harder on that wheel. The wheel will spin slower or even stop spinning entirely. This is called wheel lockup, and it can cause the car to slide or skid as the other wheels continue to spin.
In the best-case scenario, the antilock braking system and the wheel-speed sensors at each wheel will come to the rescue before then. Preventing tires from locking up during panic braking and/or braking in wet or icy weather conditions, the ABS function is a requirement on all cars made after 2013. How does it work? The ABS system is outfitted with computers and sensors of its own. At each tire, a wheel-speed sensor spits out a measurement to a computer that compares speed among all four wheels. If the computer detects an inconsistency, it will send a signal to remove boosted brake force from the slower wheel or wheels by stopping your foot from fully depressing the pedal. Reducing pressure on the brake pedal goes against all of our intuitions, but that’s what the ABS system does for us by applying and releasing force from the brake pad very, very quickly. When the system engages, you’ll feel the brake pedal suddenly jam up and start vibrating. That’s the result of the ABS system pumping the brakes in fractions of a second, automatically achieving the pulse-style braking that will free up a locked wheel and allow you to remain in control.
Wheel lockup can cause a car to slide or skid.
Driving Without ABS
The automatic braking system is a wonderful safety feature, but you won’t be damaging your car if you drive while the system isn’t working. If the ABS system is malfunctioning and you need to come to a sudden stop, try to apply pulse-style braking (aka pumping the brakes) rather than slamming all the way down on the brakes. Use your foot to tap the brake pedal lightly and quickly. Rapidly applying and releasing force to your wheels will cause the caliper and brake pads to release their clamp on the locked wheel.
Traction Control
ABS is great for helping to prevent the car from sliding during braking. Traction control (TC) and electronic stability control (ESC), also known as vehicle stability control (VSC), help control the car during acceleration, actually slowing it down when you are pulling a dangerous move. If you are taking a corner too fast and are in danger of spinning off the road and/or toppling over, these systems’ sensors and computers will slow your car down automatically to prevent you from spinning out or flipping over. Often the TC and/or ESC dashboard lights (an icon of a car with wavy lines behind its tires) will illuminate while the functions are activated.
Another nice thing about traction control: The system doesn’t require any maintenance. When it experiences a fault or failure, the TC dashboard light will flash.
BRAKE SYSTEM MAINTENANCE AND REPAIRS
PART
ISSUE
FIX
TIMING
COST
Brake Fluid
As it cycles through temperature changes, brake fluid gets grimy from chemical breakdown. Dirty fluid has a lower boiling point and begins to evaporate at the high temperatures common within your brake system. Evaporation leads to low brake fluid level, which will cause poor braking and could lead to a crash. Dirty brake fluid also causes corrosion of your brake parts and brake lines
Have your PCT drain and replace your brake fluid (aka brake exchange or fluid flush)
Every three to five years per your PCT’s recommendation
Less than $250
Brake Pads
Material will start to wear away as your pads rub against the metal rotors
Replace
The brake pads need to be replaced when they are down to 2 millimeters or 2/32 of an inch thick. Some cars have indicators on the pads that squeal to tell you when it’s time, and luxury brands tend to have sensors that illuminate a light on your dash
Look to spend about $150 per axle to replace your brake pads
Rotors
Rotors thin as they wear, and they can be further damaged by brake pads that aren’t replaced in time and create scoring and circular scratches on the rotors
Replace or machine
If you change your brake pads regularly, change the rotors at every other brake pad change. Don’t put new brake pads on a worn rotor, or you’ll be wearing out the new pads and hearing bad braking noises in no time
Look to spend at least $350 to $500 per axle to replace both brake pads and rotors. If you need pads and rotors all around (front and rear axles), you’ll be out at least $700 to $1,000
Calipers
Calipers fail from wear and tear, or if brake pads and/or rotors aren’t replaced on time; failure to replace brake pads when friction material wears away will cause the calipers to overextend themselves during braking
Replace
Variable
Look to spend at least $200 to replace this expensive part at each wheel, and a little extra to bleed the brake fluid of air
Brake Shoes and Drums
The metal springs that hold the brake shoes in place need to be adjusted from time to time. You’ll feel a soft or low brake pedal or hear squeaking when the springs need a tweak. Brake shoes and drums will also wear over time
Replace
Replace brake shoes when worn, about once every five to seven years or 50,000 miles; replace drums on every other brake shoe change, along with rotors.(Depending on how long you keep your car, you may never need to replace your brake drums.)
Look to spend an average of $150 to replace each brake shoe and $350 to $500 to replace both a shoe and a drum
Wheel Cylinders
The wheel cylinders in drum brakes will fail from normal wear and tear, or if the brake shoes aren’t replaced as needed. Not replacing the brake shoes when all friction material has worn away will cause the wheel cylinders to overextend themselves during braking
If the wheel cylinder on the right rear tire fails, the left rear wheel cylinder isn’t far behind, so mechanics often replace wheel cylinders in pairs, and the brake fluid will also need to be bled
Variable
Look to spend at least $150 for a pair of wheel cylinders
Master Cylinder
The maste
r cylinder will fail from use over time
Replace; brake fluid will need to be bled
Variable
Less than $750
Brake Booster
The brake booster will fail from use over time. The pedal will be too hard to push down when the booster fails
Replace
Variable
Around $500
Brake Lines
Brake lines often fail from corrosion caused by brake fluid and/or salt exposure and will leak brake fluid until they are replaced
Replace; brake fluid will need to be bled
Variable
Price varies depending on the number of brake lines that need to be replaced. The lines themselves are inexpensive, but the job is labor-intensive; $350 and up
Vacuum Hoses
The hoses that vacuum air from the engine into the brake booster can come loose or wear from use—without the boost, you’ll feel a hard brake
Attach the hoses back in place with hose clamps or replace if necessary
Variable
Less than $100
Antilock Braking System
If your car has antilock braking, each tire will be outfitted with a wheel speed sensor and metal “tone ring” that measure how fast that wheel is spinning. The sensors and rings are common points of failure, especially on pothole-ridden roads
Replace the individual points of failure
When an ABS warning dashboard light comes on and stays lit
Look to spend at least $100 per wheel
Machining vs. Replacing
You may have heard the term machining, turning, or cutting tossed around your local auto shop, but when it comes to rotors, most places don’t “machine” them anymore. As with so many modern parts and appliances, the cost of a new rotor has become less than the cost of the labor involved in machining one. Drums can also be machined, but they’ve become just as cheap to buy new.
Parking Brake
Also called the emergency brake, the parking brake is a backup system applied independently of the primary brakes. It can be used in case of an emergency, but it is designed to hold a parked vehicle in place. Unless you have a manual transmission, you don’t need to use the parking brake every time you park the car. If you drive an automatic and don’t frequently park on hills, use the parking brake a few times a month to prevent it from getting rusty and lonely. On some cars when the parking brake is on or engaged, the parking brake and the brake dashboard light will be illuminated.
Signs of a Brake Issue
You should be able to hear or feel the most common signs of a brake issue. None of these should be ignored.
PROBLEM: Squealing
CAUSE: A squealing noise is an intentional indicator that brake pads need to be replaced. Brake pads come with metal indicator attachments that rub on the rotor when the pad material is worn down to 3 millimeters; this rubbing is what causes the squealing noise. Most luxury cars use an electrical indicator in place of the metal attachment; instead of a squealing noise, a dashboard light will appear when brake pads are low.
PROBLEM: Grinding
CAUSE: Grinding is caused by worn brake pads and rotors. If you let that squealing go on too long and the brake pad material wears away entirely, the brake pad backing will be rubbing against the metal rotor, causing grinding that sounds like a metal chain being dragged across concrete.
PROBLEM: Shaking during braking
CAUSE: Rotors get warped or “out of round,” causing a vibration when you step on the brake pedal. If replacing the rotors doesn’t fix the problem, the vibration may be caused by your tires. If your brake pads are pretty new, only the rotors will need to be replaced. This is the only time it’s okay to replace rotors without replacing pads.
PROBLEM: Pulling during braking
CAUSE: If you feel the car pull or jerk to one side as you brake, one of your calipers may not be releasing the brake pad from the rotor. Your caliper or your brake hose may need replacing, or you may have a suspension or steering issue.
PROBLEM: Brake light on
CAUSE: No or low brake fluid. This indicator is the result of a brake fluid leak, or an urgent need to replace one or more parts of the brake system. If your brake light comes on while you are driving, pull over and check the brake fluid reservoir. (See page 173.) If there is fluid in the reservoir, drive your car to your PCT or to the closest service station; if there is no fluid in the reservoir, get the car towed to your PCT.
PROBLEM: Spongy brake pedal
CAUSE: If your brake pedal feels spongy when you press on it, there is air in your brake fluid, and the system needs to be bled.
PROBLEM: Low, soft, or sinking brake pedal
CAUSE: Brake fluid is low, brake pads or shoes may need replacing, drum brakes may need adjusting, or a brake fluid exchange is needed. If you have low brake fluid or your brake pads are worn down to 3 millimeters or less, the pedal will be soft, or easy to push, and you won’t feel resistance (the brake pads clamping down on the rotors) until the pedal is almost to the floor. That half-second delay can translate into a collision.
PROBLEM: Brakes self-apply
CAUSE: If the brakes engage as if you stepped on the pedal when you didn’t, you most likely have an issue with your master cylinder.
PROBLEM: Hard braking
CAUSE: If you press on the brake pedal and it won’t push down at all, even when you use both feet and all your weight, your brake booster (that magical Super Mario Bros. mushroom) is failing and will need to be replaced.
DIY #5: How to Check Brake Fluid and Power Steering Fluid
Being low on brake fluid or power steering fluid could be an indicator of a major issue in one of these vitally important systems. So in this section we’re going to learn to check them both. Adding the wrong fluids to the brake fluid or power steering reservoir could cause damage to the systems, so all you’ll be doing is checking the levels. If levels are low, take your car in as soon as possible to avoid a crash and/or an expensive repair. Do not continue to drive with low brake or power steering fluid.
Tools
None. All you need to check these fluids are your eyes.
Checking Your Brake Fluid Level
Brake fluid cap
Open the hood of your car and locate your brake fluid reservoir. There should be a max and min level indicator on the reservoir. If the fluid is low, you either need new brake pads or have a leak in the system. If the fluid is below the minimum level, you could find yourself without brakes while driving. Take the car to your PCT immediately.
Checking Your Power Steering Fluid Level
Power steering fluid cap
Dipstick
Open the hood of your car and locate your power steering fluid reservoir (see page 69). Check the max-min fluid level indicator on the reservoir or unscrew the cap to view the plastic dipstick.
Driving with power steering fluid below the minimum level could cause permanent damage to your steering system. If the fluid level is low, take the car to your PCT immediately.
Keep ’Em Rolling: Tires and Wheels
The only parts of a vehicle that come in contact with the ground, tires are a car’s shoes. I like to picture mine as a pair of saucy red heels. And the good news about those heels is that, like any quality pair of footwear, they should last a long time—if you care for them properly. With some tires designed to drive 60,000 miles, you may have to buy replacements only once or twice over your vehicle’s lifetime. But many of us skip the maintenance and repairs our tires require, costing ourselves more money in the long run. Even more important, neglecting your tires creates the potential for serious safety issues.
Anatomy of a Tire
The terms tires and wheels are often used interchangeably, but tires are tough, hollow rubber circles, and wheels are the round hunks of metal that the tires are placed over. Once tires are placed over the wheels, they are inflated to optimal pressure for safe and predictable driving.
There’s a miscon
ception that it’s your brakes that stop a car. But the stopping action, set into motion by your brakes, is actually finished off by the friction between your tires’ tread and the ground. That tread is super important, because it allows the tire to grip the surface of the road as you slow down. Tread also wears away over time. And when it’s completely gone, your tires won’t be able to effectively grip. Instead of coming to a full stop, you will come to a much slower sliding stop, a serious safety issue that could result in a crash.
Tires have lots of acronyms printed on them, so here’s a guide to what they mean.
The long and short of it is that driving around with bald tires is a major auto airhead mistake, but one that’s easily remedied since you can actually see and assess your tire tread yourself, using the chart showing premature or uneven wear and possible causes on page 195.
Common Tire Problems and Fixes
The wheels on that bus may go ’round and ’round—but without functional tires, nobody’s getting to school on time. Here are a few common issues and the fixes that will help keep you and that big yellow bus (with the fancy red heels) on schedule.
Incorrect Tire Pressure
Air pressure mistakes create uneven contact with the road—which spells D-A-N-G-E-R!
If you enjoy a smooth ride, you have the pressurized air inside your rubber tires partly to thank. But the air pressure inside those tires has got to be just right or your tire tread will wear unevenly, creating the potential for a flat. Too high, and the tread will show more wear toward the center of the tire; too low, and the sides will suffer.
Girls Auto Clinic Glove Box Guide Page 13