Brake failure can not only be scary, it can be catastrophic and deadly. Brakes are taken for granted as long as they work, but at some point, they can fail, creating a situation that can cancel our sojourn in this mortal coil.
In the movies involving westerns, in the wagons we see early braking systems, a curved block of wood the rubs the steel tire on the rear wagon wheel. Works to a degree. But on steep down grades they would lock the rear wheels dragging them across the surface, usually with some sort of rod running side to side through the spokes of the wheel. When the first automobiles came into use these same devices where used. Until brake bands. These surrounded a drum and where squeezed around the drum. Causing breaking.
How Does a Brake Band Work?
First some physics. The brake system utilizes the thermodynamics of converting the kinetic energy ( ½ (mass x velocity^2) of the vehicles speed to heat energy that is dissipated into the air. This is done through friction. So, keep in mind for brakes to work they convert the energy of movement into heat via friction. Another point is weight transfer. Moving forward, the normal direction of high-speed travel, on applying the braking system the weight transfers to the front wheels, hence the reason front brakes are sometimes bigger than rear brakes and the reason disk brakes first appeared on factory cars in the front. These early band systems used mechanical linkage, usually to the back wheels only and where notorious for uneven braking as keeping rods in adjustment was difficult.
Advantages of Hydraulic Brakes
One of the first major advances where hydraulics that took advantage of the non-compressibility liquids to allow braking to all four wheels. Drum brakes where the norm, with internal brake shoes that were forced outwards to contact the inner surface of the drum, a technology that dominated brakes for years until the gradual introduction of disk brakes in the 1970’s. The problem with drum brakes is ‘fade’. With the drum and brake backing where the shoes and brake cylinder mount it is almost an enclosed space. Heat builds until it is created faster than the transfer to the air providing cooling. When brakes fade there is no more slowing as the heat generation has overwhelmed the cooling. In big trucks during a runaway situation the can glow cherry red and you can see the shadow of the internal mechanisms. Heat can be so high it starts the tires to burning.
Disc Brake Components
The disk brake hangs out there in the air and has much better thermodynamic heat transfer than normal drum brakes. The disk, or rotor as it is called spins between the calipers that squeeze the rotor creating friction and heat that dissipates rapidly. The big caveat with disks is that human muscle has a difficult time applying sufficient pressure to operate the brakes. Hence, all disk brakes require power assist, created by engine vacuum or a vacuum pump in diesel equipped vehicles. Power assist is created when vacuum is applied to a diaphragm that uses the vacuum and atmospheric pressure differential to assist the braking process.
Towing & Roadside Assistance in Irving, Fort Worth, Arlington, Carrolton & Plano Texas
As with all things mechanical they need maintenance. Adjusting disk brakes is not necessary as they are self-adjusting. But leaks can develop on the hydraulic side. A perforated diaphragm can cause loss of the power assist and of course the pad lining wears necessitating their replacement. Make sure your brakes are inspected during your oil change. And be aware of any uncommon noise or a soft brake pedal. Your safety depends on it. Whenever you need towing or roadside assistance services, contact Speedway Towing & Roadside Assistance!