Disc Brakes

All modern cars have disc brakes on front wheels and disc or drum brakes on the rear axle. How do disc brakes work?

The main component of the disc brake setup is a brake calliper. The hydraulic piston(s) inside the calliper can apply clamping force to the brake disc using two brake pads. The clamping force can slow down or stop the rotation of the disc and the wheel.

A disc brake assembly

Passenger cars, SUVs and pickup trucks on the road today have a hydraulic braking system filled with brake fluid. When the driver presses the brake pedal, it pushes the piston inside the brake master cylinder that creates pressure within the hydraulic braking system. The brake fluid transfers the pressure to the brake callipers that apply brakes to the wheels. 

How a disc brakes works

Parts of a Disc Brake

Parts of a disc brake assembly

Brake Disc (rotor): 

The brake disc (rotor) is mounted on the hub and rotates together with the wheel.

During braking, kinetic energy of the vehicle converts into heat due to friction between pads and the disc. To better dissipate the heat, most vehicles have ventilated discs on the front wheels. Rear discs are also made ventilated in heavier vehicles. Smaller cars have solid (non-ventilated) discs.

Brake Pads: 

Brake pads are installed within the brake calliper, on both sides of the brake disc so that they can slide laterally, towards and away from the disc.

Toyota brake pads

A brake pad consists of a friction material pad moulded to a metal backing plate. 

Brake pads wear out with mileage. To work properly, the pads have to have enough friction material. If any of the pads are worn out close to that limit, or there is any damage to the pads, all brake pads of the axle must be replaced.

New and old brake pads

Brake Calliper: 

There are two types of brake callipers: fixed callipers and floating callipers. Fixed callipers are often installed on luxury and sports cars. Most of the vehicles on the road today have floating brake callipers similar to the one in the photo. A typical floating brake calliper has one or two pistons on the inner side.

Fixed and floating callipers

Compact cars and SUVs typically have single-piston callipers, while larger SUVs and trucks have dual-piston callipers on the front axle and single-piston callipers at the back.

Front brake callipers are mounted on the steering knuckles. Rear callipers are bolted to the rear spindles or the rear axle. In the most common design, the lubricated calliper guide pins allow lateral movement of the calliper. This movement is vital for proper brake operation. Seizing up of the calliper pins will lead to many problems.

How long do disc brakes normally last?

As a result of the friction, brake pads and rotors wear out. In an average car, disc brakes normally last for 45,000-80,000 kilometres. Worn out pads need to be replaced. Rotors can be resurfaced or replaced depending on their condition. Of course, there are many reasons why brakes can wear out prematurely, including driving styles.

Common problems with disc brakes

Common problems with disc brakes include:

Noises: Disc brakes can cause a variety of noises. Brake pads have metal wear indicators that are designed to make a metal squealing noise when brake pads wear out close to the limit. Rust build-up on the edges of the working surfaces of the rotors can cause squeaking noises. Servicing the brakes might be enough if the pads and rotors are still in good shape.

Poor-quality brake pads can also produce squeaking while braking. In some cases, squeaking can be reduced by applying a thin layer of grease to the back of the brake pads. With any brake noise, have your brakes checked as soon as possible to keep your car safe.

Warped or unevenly worn rotors: As a result of the excessive heat, rotors can warp. Mostly it happens to front rotors in heavier vehicles. 

Warped rotors

The main symptom of warped front rotors is shaking of the steering wheel that is noticeable when braking at higher speeds.

Rust on the rotors can cause the same problems. When the car is parked for days without driving, sections of the rotors rust. This causes rotors to wear unevenly: sections that were damaged by rust wear more and become thinner. The result is the same: shaking of the steering wheel and vibration felt in the brake pedal when braking at higher speeds.

Have your brakes checked. Warped or unevenly-worn rotors need to be replaced or machined (resurfaced), depending on their condition. Brake pads might also need to be replaced..

Rust damage: This problem is more common abroad in the salt belt. Brake rotors and other parts tend to rust when the car is parked outside for some time. Road salt (not in Nigeria) accelerates the corrosion process and not much can be done to stop it. 

Rotors in this car got rusted while it was parked. Only about half of the working surface of the brake disc shows a sign of contact with the brake pad. This disc must be re-surfaced or replaced.

Fortunately, we don't have serious problems with rust in Nigeria. I advise strongly however, that you  thoroughly inspect that "tokunbo" car you want to buy which has been sitting for months waiting for a buyer. Some of these vehicles are imported from areas which use salt to clear their snowy roads (salt belt). Often, there are serious rust problems just lurking. I once saw a 2003 Toyota Corolla were the entire "4 legs" (shock absorbers, linkages, bushings, calliper, rotors, ball joints etc) had to be replaced barely four months after purchase in addition to some underbody rust repair work at Abuja in 2017. It wasn't cheap. Oh boy, it certainly wasn't cheap. The owner had to "gather power".

Rusted rotors

Sticking or seized brake callipers or pads: Brake callipers (pistons or guide pins) tend to stick and seize up, especially if brakes are not serviced regularly. Brake pads can also seize up inside the calliper or inside the calliper bracket.

If caught early, servicing brakes may be enough to restore operation of the brake callipers. In some cases, the calliper will have to be replaced.

Symptoms of a sticking brake calliper or pads include dragging brakes, squeaking while driving, overheating of one of the wheels or excessive brake dust on one of the wheels. In a sticking brake calliper, brake pads tend to wear unevenly: one of the brake pads might be worn more than other pads. In some cars, sticking rear brake callipers can cause parking brakes not to release fully.

I always apply some light grease on the ends of the brake pads when changing my brake pads. They stay quite and move freely.

Brake Servicing

Servicing brakes involves taking them apart, inspecting and cleaning the excess rust and lubricating areas that must be lubricated with grease. The rotors may require re-surfacing. 

Properly functioning brakes in your car can be the difference between stopping in time and having an accident. Even if they seem to work properly, I strongly recommend having brakes checked every time you do a tyre balancing/alignment or at least once a year. Many problems with brakes can be caught early. 

Your brakes should be checked if you suspect a problem with them, for example, when you notice noises coming from the wheels or when brakes don't work as they should or when one of the wheels appear hotter than others or when the car pulls to one side while braking. 

DO NOT BLAME THE DEVIL!!!

DO NOT MAKE YOUR VILLAGE PEOPLE PROUD!!!

DO NOT MANAGE YOUR BRAKES!!! FIX YOUR BRAKES NOW!!!

Twitter and Instagram; @VverteAutoSevcs
Email; vverteautosevcs@gmail.com
Phone; 09137103730

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