When do disc brakes need to be replaced?

Updated: March 01, 2020
Most cars have disc brakes on all four wheels and some vehicles have disc brakes in the front and drum brakes at the back. How do disc brakes work? Each wheel has a brake disc or 'rotor' that spins together with the wheel, see the photo.
Disc brakes diagram: caliper, rotor, pads, thickness Disc brakes. Ford display.
When you press the brake pedal, brake pads squeeze the brake disc from both sides slowing it down or stopping completely. The kinetic energy of a moving car converts into heat.

As you drive, brake pads and rotors gradually wear out. If brake pads and rotors wear out past the safe limit, braking performance will be reduced and the vehicle will be unsafe to drive. Over time, rust buildup, excessive heat and other problems can also make your disc brakes less effective and increase braking distance. To keep your brakes working properly, they need to be inspected regularly and replaced before they lose their effectiveness.
Brakes also need to be inspected if you notice any signs of brake-related problems.
Disc brakes diagram Disc brakes.
Such signs include longer braking distance, reduced braking performance, abnormal noises (screeching, grinding, etc.), different feel of the brake pedal, pulling to one side while braking.
Car makers don't specify the mileage to replace brakes in the maintenance schedule; instead, they list brake inspections that must be done during regular services. For example, the maintenance schedule for the 2020 U.S. Toyota Camry advises to "Visually inspect brake linings/drums and brake pads/discs" every 5,000 miles or 6 months when doing the tire rotation. Brake inspections are done when wheels are removed, because some brake components are not visible with the wheels on the car. Check your vehicle's owner's manual for details.

What is a brake inspection? Car manufacturers provide technical guidelines for mechanics on the brake inspection process and specifications for brake components. Examples include minimum rotor (disc) thickness and minimum brake pad friction material (lining) thickness.
Measuring brake rotor thickness Measuring brake rotor thickness.
See the photo of worn-out and new brake pads. Based on the guidelines, a mechanic can determine whether your brakes need to be replaced or not, and whether your car is safe to drive.

How long do brakes last? On average, disc brakes last for 30,000-50,000 miles, although there are many reasons why brakes can wear out prematurely. For example, If the vehicle is parked for extended periods of time, especially in wet weather, brake rotors and other parts tend to rust. This problem is more common in regions where road salt is used in the winter. Rust causes brakes to wear sooner. If some of the brake components (e.g. guide pins) are sticking, the brakes may also wear sooner. To prevent sticking, brakes may need servicing between replacements.

What does it mean when your car needs new brakes? It means that the brake parts that are worn out (typically, brake pads and rotors) need to be replaced with new parts.
Brake pad thickness Many auto repair shops use a simple tool to measure brake pad lining material thickness.
In some cases, additional parts of the braking system might need to be replaced. For example, if a mechanic finds that the brake caliper is leaking or not functioning properly, it will need to be replaced too.

Do the rear or front brakes last longer? Front brakes do most of the braking and, in some cars, front brakes wear out faster, but in others, rear disc brakes wear out sooner. It depends on the design, material and size of the pads, load and many other factors.

Should you replace the front and rear brakes at the same time? No, it's not necessary. Front or rear brakes can be replaced independently of each other. Of course if, for example, you are replacing your front brakes and the rear brakes are getting low, it might be a good idea to get them done at once to save time.

How much does it cost to change brakes? Typical brake replacement on one axle includes replacing a set of brake pads and both rotors, as well as related hardware (shims, springs, etc.). Replacing brakes also includes servicing the components that need to be serviced, for example, cleaning and lubricating guide (slide) pins.
Worn-out versus new disc brakesWorn-out versus new disc brakes.

In an average car, replacing brakes (pads, rotors and hardware) on one axle costs from $400 to $750. The price depends on where you decide to do the repairs and what kind of parts will be used. Replacing brakes at a dealership using original (OEM) parts is more expensive. Doing the job in an independent repair shop with aftermarket parts is usually cheaper.

Are aftermarket brakes as good as OEM? Some aftermarket brake parts are of very good quality while others are cheap, and usually for a reason. If in doubt, OEM parts are always a safe choice. It's also a good idea to use OEM parts while the vehicle is under warranty. If you want to use aftermarket parts, request high quality parts from a reputable brand. Although in general, aftermarket parts are cheaper, we have seen cases where OEM prices were close or even cheaper than aftermarket. This means, check the dealer prices first.

Is it better to use new rotors or resurface the old ones? In some cases, old brake rotors can be resurfaced or 'machined' instead of replacing. In this case, replacing brakes on one axle includes replacing brake pads and related hardware, machining both rotors and servicing all related components.
New pads and rotors New pads and rotors.
Car makers specify the requirements (e.g. minimum rotor thickness) when brake rotors can be machined and when they must be discarded. Replacing rotors is always a preferred option, since machining makes rotors thinner. Plus, the overall price of the brake replacement is usually not much different whether the rotors are machined or replaced.

There are situations where your mechanic may recommend reusing the brake pads and replacing or machining the brake rotors; for example, if the brake rotors are warped or rusted, but the brake pads are still in good shape. In other cases, only the brake pads can be replaced if the rotors are in good condition and can be safely reused. When deciding between different repair options, safety is always the first consideration.

Parking brake: In most cars, rear disc brakes serve as parking brakes. Other vehicles with rear disc brakes have separate mini drum parking brakes built within the rear disc hubs. Separate parking brakes are also replaced when they are worn out. The parking brake might need to be adjusted whenever the rear brakes are serviced or replaced. Many modern vehicles have an electronic parking brake (EPB) with electric parking brake actuators that are attached to the rear calipers. Whenever the rear brakes are serviced or replaced, the electronic parking brake might need to be set into service mode.