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When to Change Brake Pads

Updated on June 24, 2016
Old and new brake pad.
Old and new brake pad. | Source

Do you know when to change brake pads on your car?

Of course brake configurations on some modern vehicles come with reliable systems that alert you of worn out pads that need to be replaced. In addition, car manufacturers suggest service intervals you can follow as well. But not all vehicle models come with an alert system, and no two drivers wear their brake pads at exactly the same rate. Further more, different vehicle models and driving patterns cause pads to wear at a different rate.

But knowing when to change brake pads is more than just making an inspection for pad wear.

Besides brake fluid, pads—and shoes on some older vehicle models with rear brake drums—are the only component in the system in need of regular replacement, but pads can also give you signs of potential system trouble. Pads may become the target of physical damage when problems begin to develop in the brake assembly. However, you can only catch and prevent many of these problems by learning to recognize the potential signs of brake problems through sounds, physical symptoms and visual clues.

Follow this simple guide to verify when to replace your brake pads.

Index
Beware of Sound Warnings
Watch for Physical Symptoms
Time Saving Brake-pad Wear Inspection
How to Remove a Brake Pad for Inspection
Visual Clues to Look For
The Rule On Replacing Brake Pads
Quiz: Test Your Knowledge of Car Brakes

Beware of Sound Warnings

Worn out or damaged brake pads may produce sounds you should pay attention to and investigate as they appear.

* For example, some brake systems include a metal tab (wear indicator) that rests next to the brake pads. When the brake lining (the friction material that rubs against the disc rotor) has worn down close to 1/8 inch (3 mm), the metal tab begins to rub on the rotor's friction surface, causing a squealing noise.

* A grinding noise on the other hand, main indicate that your pads or shoes have completely worn out. This means the backing plate of the pads or shoes are pressing against the rotor or drum every time you slow or stop the vehicle. If you fail to replace the pads or shoes soon, you most likely need new rotors or drums as well.

* Other vehicle models include a wear sensor in the pads and will alert you instead with a warning light on your dashboard. But, if you hear a screeching, metal-to-metal sound instead, it should alert you to a potential problem with your brakes.

* Still, other problems related to brake pads or shoes may cause your brakes to produce sounds as well. For example, you may hear a squeaking sound when depressing the brake pedal. This may indicate the presence of foreign material on the linings, or even a glazed lining. Also, a light layer of rust may settle on the disc rotor if you leave your car seating for a few days exposed to rain or humidity; however, braking action will wear out the rust and the squeaking sound will go away, if your brakes are working properly.

Whatever the cause, whenever your brakes become noisy, visually inspect the pads, correct the problem and replace them as necessary.

New set of brake pads.
New set of brake pads. | Source

Watch for Physical Symptoms

Besides sounds, some physical symptoms coming from the brake system of your car may also indicate problems with the brake pads, shoes, or a mechanical component in the brake assembly. For example:

* You notice that your brakes engage too quickly when depressing the brake pedal.

* Suddenly you need to push the brake pedal harder to slow down or stop your car.

* The car pulls to one side whenever you apply the brakes.

* You feel the brake pedal vibrate when slowing or stopping.

A number of issues may cause one or more of these problems: You may be dealing with contaminated brake pads, shoes, rotors or drums; brake fluid, grease, or rust may have found its way onto the pad's or shoe's friction material, rotor or drum; pads are wearing unevenly; even system mechanical problems can cause some of these problems.

Make a visual inspection of the brake pads and shoes and replace them if necessary. For more on diagnosing brake symptoms, check this article on brake problems symptoms.

Time Saving Brake-Pad Wear Inspection

Here's a quick way to save time when checking your pads for wear, if you haven't had any problems with your brakes:

* On some vehicle models, you can quickly check the thickness of the pad by looking between the rim spokes. The lining should be thicker than the backing plate. Otherwise, it's time to change pads.

* Also, some brake pads come with a slot on the middle of the lining. When this gap wears away, you know it's time for new pads.

New pad installation.
New pad installation. | Source

How to Remove a Brake Pad for Inspection

Use the next procedure to remove the pads you want to visually inspect.

1. Park your car on a level surface and loosen the wheel nuts (but don't remove yet) on one of the front wheels.

2. Then, raise the wheel off the ground using a jack and secure it with a jack stand.

3. Apply the parking brake, chock the rear wheels to prevent your car from rolling and remove the wheel.

4. Then, spray the brake assembly with brake parts cleaner and wipe the assembly clean using a lint-free paper towel, if necessary.

5. Mounted on the disc rotor, you’ll see the brake caliper. The caliper holds the brake pads in place on each side of the rotor and houses the cylinder and piston that pushes on the rear pad against the rotor.

6. Remove the one or two caliper mounting bolts. These bolts are located behind and towards the bottom of the caliper assembly, one on each side.

* If your caliper only comes with one mounting bolt, you can unscrew this bolt and swing the caliper off the rotor to access the pads.

* If it comes with two mounting bolts—one on each side—unscrew these bolts, pull the caliper off the rotor and secure it to a suitable component using a piece of heavy wire. This will prevent the caliper from hanging loose and damaging the brake hose attached to it.

7. With the caliper off the brake rotor, you now have access to the brake pads.

8. Make a note of each component position linked to the brake pad like the anti-rattle clip, support spring, retainer screw or any other part. This will help you replace the pad and related parts in their original position after you finish your inspection.

9. Then remove one of the pads for inspection (refer to the next section).

After inspecting or getting a new set of pads, follow these steps in reverse order to reinstall the pads and wheel. But, when mounting the tire on the wheel assembly:

10. Tighten the lug nuts snugly.

11. Lower your vehicle and tighten the nuts gradually, following a crisscross pattern.

12. Finally, tighten the lug nuts to the torque listed in your vehicle service manual for your particular vehicle. You can buy an inexpensive vehicle service manual for your particular car make and model at most auto parts stores or online.

Follow this same procedure to inspect the other set of pads.

The next video gives you a run down of the main inspections points.

Visual Clues to Look For

A visual inspection of the brake pads and shoes can also help reveal lining condition, potential system problems you may not be aware of, and prevent an expensive repair—or an accident.

1. When checking the brake pads or shoes, closely inspect the friction surface.

If you see signs of damage like cracks, discoloration or glazing, you'll need to replace the pads and have your brakes inspected to make sure you're not dealing with problems in the brake system that might've caused damage to the pads.

2. Look around the edge of each pad's lining and locate the thinnest side. Measure the thickness of this side (you may want to use the depth gauge on a vernier caliper) and then measure the thickness of the board where the lining is mounted on. The part of the lining you measured earlier should be thicker than the mounting board. Otherwise, replace the pads.

Note: A slight difference in thickness from one side to the other of the lining is normal. However, if the difference is significant, you will need to have the brake system inspected to find the cause and replace the brake pads as well.

On brake pads, the lining should be no thinner than 1/8 inch (3 mm) or thinner than the backing plate they are mounted on.

3. Also, check the brake shoes (if rear wheels fitted with drums) for signs of cracks, discoloration or glaze. Replace them as necessary and correct any problems.

4. Also, measure the lining on the shoes. The lining material should be thicker than 1/16 inches (1.5 mm) or thicker than the backing plate they are attached to, says James E. Duffy on Modern Automotive Technology.

5. Make a visual inspection of the brake rotor (and drum, on brake shoes), specially if your brakes have become noisy. Groove marks on the rotor or drum means you'll need to turn (machine) the rotor or drum to smooth the surface again. If the grooves have cut too deep—or the friction surface is worn—or you see cracks on the braking surface, you'll need to replace it.

6. Also, check for ridges at the outer edge of the brake rotor or drum. If the ridges are fairly pronounced, resurface the rotor or drum, or replace them, as necessary.

The Rule On Replacing Brake Pads

If you decide to replace the pads on a wheel assembly, always replace the set on the opposite wheel assembly as well. For example, if you are replacing the pads on the right front wheel, replace the pads on the left front wheel. This will prevent braking performance issues.

Now you know when to change brake pads. Don't overlook your pads, shoes and the brake system. Keep this guide handy and use it whenever you want to decide whether your brakes need a new set of pads or shoes—inspect them at least every six months. Also, use this guide when you hear unusual sounds coming from your brakes, when you notice a physical symptom. Then, replace the brake pads, if you have to, or have an expert do a more thorough inspection and do the necessary work. Over time, a quick inspection can save you money in brake maintenance, diagnostics and repairs. And you'll be safer on the road.

Test Your Knowledge of Car Brakes


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