Several telltale signs will let you know when to change brake pads or other components of your braking system. If you hear a squealing sound or your car pulls to one side when braking, you probably need your brakes checked. A low brake fluid warning light on your dashboard can also indicate an issue.

How brakes work — and how they wear down

A braking system consists of both mechanical and hydraulic parts. Every time you put your foot on the pedal, the master cylinder pushes brake fluid into a hydraulic caliper behind the wheels. Pistons in the calipers squeeze the brake pads against the metal, disc-shaped rotors to stop the car.

This constant squeezing and releasing wear away at both the pads and rotors over time. It also creates significant heat. “As the pads get lower and lower, they don’t dissipate the heat as much,” says Bruce Chidsey, vice president of automotive technical support for AAMCO Transmissions and Total Car Care. “And that causes them to wear out even faster.”

Symptoms of bad brakes

A squealing sound

According to Chidsey, one of the signs you need new brake pads is a squealing noise. That annoying sound is from the brake pad’s wear indicator, a small piece of metal that vibrates against the rotor when friction has worn the brake pads down to a minimum thickness threshold. Typically, that noise means you have about 2/32 of an inch of brake pad left. And that’s not much. In the 15 states that require regular vehicle safety inspections, that thickness is as low as the pads can get and still be considered adequate for driving.

“When your brakes squeal,” Chidsey says, “that’s when you start damaging other parts.”

Your car veers to one side

If your car pulls to one side when you engage the brakes, that’s another indicator that you may need new brakes or new brake pads. Pulling to one side indicates a problem with the brakes on the opposite side of the car. (Essentially, you’re only getting braking power to one side, causing the opposite side to swing out.) The cause might be a jammed caliper piston getting in the way of the braking operation or overly worn brake pads.

Low brake fluid level

Low brake fluid is another signal that you need new brakes. If your brake light illuminates on the dash or your brakes feel less responsive than normal, take your car to the shop and have your fluid levels checked.

“It could mean you have a leak in the system,” Chidsey says. “Or it could be a sign that your brake pads are worn. If that’s the case, the caliper pistons will extend out as the pads wear down, causing brake fluid to fill the space behind the caliper piston lower in the reservoir. But don’t just have your mechanic or a service professional top it off. That brake fluid went somewhere, so have them find out what you’re dealing with.”

When to replace brakes

With brakes, your ideal maintenance plan is to replace the pads before they wear down too much and cause metal-to-metal friction in your brake system. That’s because rotors and calipers are more expensive to replace than new brake pads alone. If you want to know how to tell if you need brake pads or rotors, listen for a grinding sound. If your brake pads and rotors are making a grinding noise, chances are it’s too late, and replacing your pads and rotors is going to be necessary. Get your brake system checked routinely to catch them from wearing too far before you hear that awful sound. Learn more about common causes for your noisy brakes.

Because your brake pads are behind the wheels and difficult to see, let alone track their wear, Chidsey advises having your technician check them for you.

“If your mechanic tells you that your brake pads are worn down to 3/32 of an inch or less, you’re getting close to the end,” he says. “And remember, there’s nothing wrong with getting them changed out a little early just to be safe.”

How to extend life of your brakes

If you want to keep your brake pads in good shape for as long as possible, practice good driving habits. Don’t accelerate too quickly or brake too quickly. Don’t ride your brakes. And don’t forget to take your emergency brake off while driving.

“If you give yourself enough space between cars to avoid jamming on the brakes, they’re going to last longer,” says Chidsey.

Also, keep in mind that if you’re consistently hauling a significant amount of weight, towing a trailer, or carpooling to work, you may need to get your brake pads replaced more frequently. Extra pounds in the car translates to faster brake wear because it takes more force to slow down.