As he was driving on Gaddafi Road in Kampala, Edgar Kaweesa realised that there was noise coming from under his car.
When he took his car to the mechanic, it was inspected and he was informed that his brake pads were worn-out and needed replacement.
“It is when I replaced the brake pads that the sound disappeared. The mechanic also told me that if I had continued driving the car with those brakes, I was to damage my brake discs,” Kaweesa recalls. Kaweesa’s scenario is just one of the many motor vehicle brake experiences that motorists encounter unexpectedly while on the road.
What they are
To Peter Amadi, a mechanic at Dalas Auto Clinic in Bunga, brakes are a system that helps a driver to stop or a system that brings a car in motion to stop. Depending on the technology of the car, Amadi says there are vehicles that were manufactured with the Anti-lock Braking System (ABS) and those that do not have the ABS.
“The ABS doesn’t just lock itself and stops. It is instead the car computer that studies the car speed and stops it even if the driver engages the brake pedal to stop the vehicle manually. As the driver engages the pedal, the computer studies the car tyres to identify one that is light,” Amadi says, adding that with cars that have the ABS, when you engage the brake pedal, it tends to out up resistance from the foot and that you have to drive carefully on a highway; not at a very close following distance.
How the brake system works
Amadi explains that when a driver engages the brake pedal, a vehicle has a rod that connects the brake pedal to the brake booster.
The brake booster then receives hot air from the engine. In the booster, there is a diaphragm which helps to push the hot air into the master cylinder.
“It is called the brake booster because there is a diaphragm inside the booster which receives hot air from the engine to make it warm so that it can move easily to create the friction to push the brake fluid to the tyre braking system,” he says.
When a driver switches off the engine and they are going down the hill, the vehicle cannot brake if it has a booster because it is not receiving any hot air from the engine.
The other important part in a brake system, Amadi says, is a brake pipe that is responsible for transporting the fluid from the master cylinder to all the four tyres. Each of the tyres, he notes, either has a cylinder or a caliper.
“If the tyre uses a drum, it has a brake cylinder and If it at the front, it uses a caliper, depending on the force applied onto the brake pedal, the brake fluid comes with force to push the piston to hold the brake pads and the brake pads will then hold the brake disc,” he explains.
It is mostly vehicles that are manufactured with modern technology that have the Anti-lock Braking System (ABS).
“When you have a car that has ABS, you have to drive following the leading driver creating a distance between you and them. If you are driving fast and the car doesn’t have the ABS, there are two things that are likely to happen; it either brakes or skids or it locks the tyres and you role depending on the driving speed.
But if you have ABS, the car cannot skid or role off the road. The ABS helps the driver to control movement of the vehicle,” Amadi advises.
The hanger is also one of the other parts in a vehicle brake system and its purpose is to hold the caliper to the disc.
When you engage the brake pedal, the brake fluid is pushed from the master cylinder through the brake pipe to the pistons or the master cylinder.
As part of the brake system, the brake drum always has either the leading or the trailing shoe. When you engage the brake, the piston moves and the shoe contacts the drum to stop the car. The brake disc is also stopped by the brake pads.
“If a car has a brake disc, it must have a brake pad. If it has a brake drum, it must have brake shoes, one leading and the other trailing,” Amadi says.
He adds that when you open the rare drum of some cars such as the Toyota Premio, the leading shoe is worn out to look more like a razor blade but the trailing shoe is still intact.
“When you brake, the leading shoe is the first one to control the car and this explains why it wears out fast,” he clarifies.
Some of the bad driving habits that damage brakes he says include instant braking.
Signs of worn out brakes
According to Vincent Lutaaya, a mechanical engineer and the director of Triangle Auto Repairs, one of the signs of worn-out brakes are a screeching sound coming from the tyres when you try to brake.
Additionally, when your car takes a few seconds to stop after you have stepped on the brake pedal and when your pedal goes down to the floor when you step on it is a sign that they need to be replaced.
Types of brakes
Paul Kaganzi, a mechanic at Palmtech Garage in Naalya, says different brake systems generate varying amounts of soot depending on two main factors; the quality of brake pads used or condition of discs on your wheels.
There are mainly three types of brake pad material that cause soot on the Ugandan market: the organic type (pressed pad material that disintegrates easily) and semi-metallic which lasts longer and produces less soot.
Ceramic brake pads, Kaganzi says are a special type which produce the least dust or soot but tend to have a little longer braking distance. Black dust at the front wheels can also be disintegrated metal from warped or grooved brake disc rotors.
“Brake discs are sometimes warped or develop grooves if poor quality semi metallic brake pads are used and pads are not replaced on time,” he cautions.
On your vehicle, Kaganzi advises that you can mitigate this problem by avoiding buying the cheap brake pads and trying to buy those that are genuine from leading or independent spare parts dealers. It is better to ask about the material composition of brake pads you intend to buy. To reduce brake dust from discs, he advises that you skim the discs within acceptable width with a lathe machine to eliminate grooves.
This can be done using sand paper to reduce soot during brake service or outrightly replace them if they wear beyond recommended width as advised by your mechanic.