Wondering When To Change Brake Pads? 5 Signs To Know

By: Michael Franco  | 
A mechanic works on a vehicle's brakes
Having a certified mechanic periodically check your brakes ensures that your auto is safe to drive.

When you're driving along the highway on a sunny day with your windows down and your radio volume up, it's easy to forget that you're in a massive chunk of steel and glass hurtling at high speeds. Should you suddenly need to stop, well-maintained brakes are a must. So, you're probably wondering when to change brake pads and other components.

Brakes may not be the sexiest part of a car, but they're certainly one of the most crucial. Paying attention to the warning signs that indicate a need for service can mean the difference between life and death on the road. With this in mind, here are five signs that just may help you put the brakes on a serious accident in the future.


5: Worn Brake Pads

Parts of a disc brake
The parts of a disc brake.
© 2000 HowStuffWorks

Most cars use disc brakes. A hydraulic system filled with brake fluid triggers a set of padded clamps known as calipers, causing them to squeeze together on a disc known as the rotor. The friction that occurs between the pads and rotor eventually stops the car. Over time, the pads will begin to wear thin, which means they'll become less effective at slowing and stopping your car. Generally, drivers are advised to replace brake pads sometime after 30,000 to 35,000 miles on urban roads. Break pads of vehicles that mostly do highway driving may be good through 80,000 miles.

Fortunately, checking the thickness of your brake pads — those that squeeze down on the calipers — is a straightforward procedure. All you need to do is look between the spokes of your wheel to spot the shiny metal rotor inside. When you find it, look around the outer edge where you'll see the metal caliper. Between the caliper and rotor, you'll see the pad. You'll have to estimate, but generally, your pads should be at least one-quarter of an inch thick. If they're any thinner than that, it's a good idea to look into brake pad replacement.


If your car wheel isn't designed in such a way that you can see through the spokes, you'll have to remove the tire to see the rotor and pads. In either case, while you're looking, it's also a good idea to inspect the rotor itself. It should be relatively smooth. If you see any deep grooves or pits, it might also be time to replace it.

4: Strange Noises

A brake pad wear indicator
Brakes pads come equipped with a wear indicator that squeals when your pads need replacing.
Photo courtesy AutoZone/© 2000 HowStuffWorks

Your mom always told you that blasting music in the car wasn't good for your ears. Well, it's not good for your brakes either. That's because one of the warning signs that your brakes need servicing can come from a small indicator in your braking system that emits a high-pitched squeal when your pads need replacing. And, while this sound is loud enough to be heard even when the windows are up, it might be tough to hear with Lady Gaga blaring from the stereo.

In addition to the squeal from the sensor, you'll also want to listen for a harsh grinding noise. A grinding sound may mean you've gone completely through your brake pads and now, when you apply the brakes, the metal of the calipers is grinding against the metal of your rotors. Not only is this an ineffective way to stop your car, but chances are good that you'll also damage your rotors. Thus, turning a relatively easy and inexpensive pad job into expensive repairs like a rotor resurfacing or replacement. It's best to avoid costly repairs like that.


3: Pulling

Has your car ever felt like it has a mind of its own? As if it wants to make right- or left-hand turns while driving or braking? If so, this could indicate a problem with the braking system. The cause of this pulling might be a stuck caliper. Because such a scenario would cause friction on one wheel and not the others, your car can pull to the side where the caliper is stuck.

Two other brake-related scenarios that could cause a car to pull would be a collapsed brake hose that would cause your calipers to move unevenly when applying the brakes, or uneven brake pads, which would also apply different amounts of pressure to different wheels.


Pulling, however, doesn't always indicate a problem with the brakes. The cause could also come from unevenly inflated or worn tires, poor alignment or a problem with your vehicle's suspension. This is why, if your car begins to pull, you'll want to pull it into the nearest mechanic's shop you locate for a full evaluation.

2: Vibrations

If you've ever had to execute an emergency stop in a car with antilock brakes, then you're familiar with the type of rapid brake-pedal pulsing that comes from the quick grabs the system applies to the rotor to slow the car. However, if your brake pedal pulses in this way under normal braking circumstances, you could have a problem.

Generally, a vibrating brake pedal indicates warped rotors. Their uneven surfaces will thrum against the brake pads, and you'll feel the feedback through the brake pedal. Rotors usually only warp when they're under extreme stress for an extended period. The friction-generated heat caused by driving down steep mountainsides or by stopping frequently while towing something heavy, for example, can cause the metal of the rotors to change shape.


If you haven't stressed your brakes recently but you feel vibrations in the pedal, you may have misaligned wheels. In either case, it's best to see a mechanic for diagnosis.

1: Temperamental Pedal

Resurfacing a rotor
Resurfacing rotors can smooth any unevenly-worn areas that make your brakes grab immediately.

In addition to thrumming, your brake pedal can give you other indications that your car's braking system might need examining. A mushy pedal, one that goes practically to the floor before engaging the brakes, could indicate worn pads or a problem with the hydraulic system, such as air in the line, an air leak or a brake fluid leak.

To check for a fluid leak, put an old white sheet or piece of light cardboard under the car overnight. In the morning, examine any fluid that collects. Brake fluid will be practically clear and the consistency of cooking oil.


The opposite of a mushy pedal is one that causes the brakes to grab immediately at the slightest touch. This could indicate an unevenly worn rotor, dirty brake fluid or contamination of the fluid by moisture. You can solve such a problem with a relatively inexpensive change of fluid that you could do yourself or have done at your mechanic's shop.

Finally, if stopping the car seems akin to Fred Flintstone putting his feet through the bottom of the car to bring it to a halt, you might have a brake line obstruction or a problem with the vacuum system. Both situations would make the brake pedal extremely hard to operate and require immediate servicing.


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