August 14

2007 Mazda CX9 – Rear Brake Pads And Rotors

Auto Repair, Mazda


This weeks featured service is a Rear Brake Pad and Rotor Replacement on a 2007 Mazda CX9, brought to us by a client from Dunbar, Vancouver.

Mazda CX9

2007 Mazda CX9

While a rear brake replacement is hardly an unusual service at our shop, or many other shops for that matter, this particular repair shows a great example of the care and detail that we put into this service.

The very first step before brakes are repaired is a detailed inspection. At our shop we start with visually inspect all components. We measure the thickness of the brake pads and rotors, or drums and shoes. We test the callipers and wheel cylinders for leaks and proper movement. We test the brake fluid. From there we can determine what needs to be replaced.

There is much more to a brake job than simply replacing brake pads. Let’s look at the individual items that require attention. These are all components that we addressed during this rear brake job.

1. The brake rotor. Otherwise known as the brake disc. This component is attached to the wheel hub and usually held in place by the wheel. Rotors are made of iron and vary in quality from car to car and from parts brand to brand. There are cheap rotors, mid priced ones, premium quality and high performance options available for most vehicles. Generally speaking cheap rotors warp easily and wear quicker.

Usually by the time brake pads wear out rotors are also worn out. Rotors are prone to rusting as they are composed of bare metal and exposed to the elements. While they can be machined on a brake lathe this practice has largely disappeared as many shops no longer have a lathe. Fortunately rotors are reasonably priced and a better brake job is done by using new rotors as they are of optimum thickness which helps disperse heat quickly.

Mazda CX9

Old brake rotor, note the excessive rust inside the drum area (center). This is where the park brake shoes apply.

Mazda CX9

New brake rotor

2. Wheel hub. This is where the brake rotor sits and is found sandwiched between hub and wheel. By the time the brakes wear out the hub usual gets rusty. Cleaning the rust corrosion from the hub is critical for a proper rotor fit and to prevent premature warpage and brake shudder.

Mazda CX9

Wheel hub before cleaning. Note the rusty surface.

Mazda CX9

Wheel hub after rust was removed. The parking brake shoes sit behind the hub.

3. Brake caliper. The caliper is the part that squeezes the brake pads against the rotor. It has one or more fluid filled pistons that operate when you press your brake pedal. There are often other sliding components with the caliper and keeping these parts free of corrosion and well lubricated is critical to long brake pad life and efficient brake operation.

The brake pads sit inside the caliper bracket and move slightly back and forth with every brake application. Over time rust corrosion sets in and causes pads to stick. Often pads will wear out prematurely when this happens. An important part of doing a quality brake job involves cleaning, removing corrosion and lubricating these critical moving parts.

Mazda CX9

Brake caliper bracket with shim removed. Note the rust corrosion. This causes the pads to stick and wear out prematurely.

Mazda CX9

Caliper brake after sandblasting away the rust. The shim below is new.

Brake caliper pistons can also seize up and so can the slider pins. When this occurs the calipers need replacement.

4. Brake pads. The brake pads are generally made of a composite material softer than the brake rotors. Once upon a time they were primarily made of that fabulous mineral asbestos. As with rotors, there is a wide variety of product offerings from cheap quality to premium to high performance. Generally we like to use as close to the original manufacturers type of pad as possible. This ensures good braking with minimal squeaks and squeals and good durability. On the subject of durability, many good quality aftermarket pads will outlast the OEM installed pads, sometimes by a substantial margin.

Mazda CX9

Rear brake pads. Old pad on left and new pad on right.

So there are the brakes and a list of components and steps to doing a proper long lasting brake job. Following all of these procedures ensures that the job is done correctly. It is what we do every time at Pawlik Automotive.

For more information on the Mazda CX9 click here

For more about disc brakes click here

About the author 

Bernie Pawlik

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