Your Guide To Brake Servicing

As the brake is such a fundamental safety item, Rob Marshall explains that any brake repairs should be made as quickly as possible.

Brakes convert kinetic (or movement) energy into heat, via friction. Components, therefore, wear out and brake servicing is essential.

Should you be daunted by performing brake repairs yourself, you should entrust the work to a suitably-qualified technician. Brake servicing requirements differ between vehicles and, should you pursue the DIY route, invest in a good-quality workshop manual for more specific advice.

DISC BRAKE SERVICING

brake servicing
The components of a typical disc brake

Virtually every modern car is equipped with disc brakes on its front hubs. Some high-performance vehicles have them on the rear as well.

Car disc brakes use the same operating principles as those fitted to some bicycles; a pair of brake pads is forced into contact with a rotating brake disc, via a calliper.

Over time, the friction surfaces will wear away and the brake pads and discs will need replacing. Should the brake pad’s friction material be allowed to wear out completely, the metal backing will be brought into contact with the brake disc, which will damage its surface severely.

When you are replacing either brake pads or discs, they must be changed in axle pairs and never on just one side.

CURING SQUEAKY BRAKES

Corrosion can form on the brake disc’s outer and inner edges and this can rub against the calliper causing squeaky brakes. This flaky rust can be chipped away with care from the disc’s edges.

copper

 The use of copper grease during assembly reduces the risk of annoying brake squeal

Brake pads vibrating in their callipers can also cause squeaky brakes. Cleaning both the pads and callipers is recommended, prior to placing a light coating of copper grease to the pad backing and its anti-rattle shims.

Never confuse squeaky brakes, which result rarely from a serious fault, with a more severe grinding noise.

 

SERVICING DRUM BRAKES

 drum brakes

Drum brakes are fitted to the rear of many cars, although high performance models often use disc brakes both front and rear

Many cars are fitted with rear drum brakes, which are not only operated by the footbrake but also the handbrake (or parking brake).

Instead of using pads, a pair of shoe linings is pressed outwards, against the inside of a cast iron drum, by a wheel cylinder. The linings are then returned to their original position by several strong springs.
drum brakes

The internal parts of a typical drum brake (drum removed)

 

Drum brakes can fill with dust, which can result in either squealing brakes or the linings sticking to the drum intermittently. Removing the lining dust is, therefore, a worthwhile brake repair. Do not blow the dust away, use brake cleaner instead.

The wheel cylinder can also leak brake fluid, which contaminates the linings and could result in either partial or total failure of the braking system. Never reuse linings (or disc brake pads) that have been soaked in brake fluid.

Some brake drums incorporate the wheel bearing and the assembly is retained by a single Nyloc nut. In most cases, this should be renewed after brake repairs are completed.

hadndbrake

 When disc brakes are fitted to the rear hubs, be wary that some models are also equipped with a diminutive drum brake for the handbrake

Some rear disc brake equipped cars are fitted with a separate drum brake for the hand/parking brake, situated within the wheel hub. This must also be inspected for worn-out linings and broken return springs.

OTHER CONSIDERATIONS

As the footbrake is operated hydraulically, every metal and rubber pipe should be inspected for rust, splits and leaks, during brake servicing.

 brake failiure

Rubber brake lines deteriorate with age. Metal brake lines often corrode and both can cause either partial or entire brake failure, if not attended to

 Brake fluid absorbs heat and possesses a high boiling point. Most types attract atmospheric moisture (they are hygroscopic), which makes the fluid more susceptible to boiling. Should this happen, you will experience almost total brake failure. It will recover after cooling but to prevent boiling, the fluid should be renewed every two years.

Should air contaminate the hydraulic system, the brake pedal travel will increase and the brakes will become less effective. Air can be bled from the system, via the bleed nipples.

Modern vehicle brakes have been enhanced to include ABS, Stability Control Programs and regenerative energy systems. These developments do not require any special maintenance but faults can occur as the car ages.

Finally, check the condition of the hand/parking brake and its cables, which operate on the rear wheels for most models. The wear in rear drum brake linings is often compensated by an automatic adjuster, which operates via the handbrake, so ensure that it works correctly.

Take care with servicing your brakes and you’ll both save money and ensure the safety of both your vehicle and its passengers.

About 

GEM Motoring Assist are a breakdown cover company and road safety charity that has been serving motorists for over 80 years.