Flawed brakes? Unscrew the brake drum to check the faults

The very utterance of the word drum equates to a sense of rhythm, tempo and beat, while the psyche travels to timpani, cymbals and gong, as also tambourine, maracas and celesta. However, the brake drum (or b, since these are always used in plural form) is a different cup of tea. It has got nothing to do with music or beat but is a vital component of a vehicle’s braking system known as Drum Brake, that help slowing down its momentum or stop it altogether, if necessary. As it resembles the shape of a drum sans the stretched top, the term has come to stay.

However, to know more about brake drums, it may be relevant to have a firsthand idea of how hydraulically operated drum brakes work. To begin with, the system comprises the following components:

• Brake pedal

• Master Cylinder

• Wheel Cylinder

• Flexible pipes

• Hydraulic fluid

• Brake Drum

• Brake shoes

• Brake linings

• Springs

• Back plate

When the driver of a vehicle steps on the brake pedal, several things take place simultaneously. For instance, it pressurizes the hydraulic fluid in the master cylinder, which in turn pressurizes the wheel cylinder through the flexible pipes and as a result, the curved brake shoes with linings riveted upon them rub against the inside of the brake drum, causing friction. This slows down the revolution of the brake drum and consequently the speed and velocity of the vehicle. If more force is applied to the brake pedal, the brake shoes literally jam against the brake drum, causing total stoppage of the brake drum and the vehicle comes to dead stop.

However, when the driver takes off the foot from the brake pedal, the pressure is released while the springs attached to the brake shoes pull in the brake shoes whereby the brake drum becomes free again and the vehicle resumes its movement.

What to do if you suspect brake drum fault

First of all, jack up your vehicle in a such a way that both rear wheels leave the ground, so that you can attend to both the brake drums at one go, because if you rectify the fault in one and leave the other unattended, the car will drag to one side whenever the brakes are applied.

Remove the wheels and also remove the brake drums by unscrewing them for inspection and servicing. The next step involves resurfacing through a process called Brake Lathe Resurfacing, provided there is enough metal to withstand the machining. In fact, there should be 0.030 inch or o.762 mm left for wear after the machining procedure has been carried out.

Next operation entails the cleaning of the resurfaced drums that invariably contain millions of miniscule metal parts lodged in the open pores of the newly machined surface. If left unclean, these particles would become embedded in the brake lining, causing damage to the brake drum.

The best thing to do would be the use of hot water to clean the brake drum thoroughly and then to dry it with the help of air pressure generated through a compressor.

An alternate method involves wiping the inside of the brake drum with a lint-free cloth dipped ina brake cleaning solvent and allowing it to dry itself. However, this operation needs several repetitions till all traces of minute metal shavings have been completely removed.

Finally, re-install the brake drums; check free movement of the drums as well as braking effect after pressing the brake pedal. And Et voila, the job is over.

Postscript

Since most contemporary vehicles are equipped with drum brakes for the rear wheels while disc brakes work for the front wheels that need minimum attention, periodic inspection and checking of the former is important for the safety of the vehicle, regardless of whether it is sedan, convertible or a SUV.