Brake Shoes
No matter how complex and computer operated today’s vehicles become, there are
very few things more important than the
brakes. Most vehicles on the road
today are equipped with what is called a disc-drum set up. This refers to the style
of brakes front and rear of the vehicle, disc being fronts and drum the rears. Some
vehicles have a disc-disc set up (disc front and rear), which is the newest and
most efficient of the combination used. Older vehicles used a drum-drum set up;
this combination doesn’t provide good stopping power and hasn’t been used for years.
Drum brakes were the standard for many years in the automotive industry but they
were phased out as the front brakes in favor of disc brakes in the late 60’s and
early 70’s depending on the manufacturer. In this article we will talk about the
brake shoes, which are the friction material for the
drum brakes.
Brake shoes come in sets of four, two for each side. There are two different
brake shoes per side, a primary shoe that has a little less friction material on
it and goes toward the front of the vehicle and the secondary shoe that has more
material and faces the rear of the vehicle. Some vehicles use shoes with the same
amount of friction material, on those it doesn’t matter which shoe is facing front
or rear. When you push the brake, hydraulic pressure forces the shoes out making
contact with the inside of the brake drum, this is the friction that stops your
vehicle. The
emergency brake
on a disc-drum combination is also the job of the brake shoes, while mechanical
in nature, the emergency brake uses the same principle of forcing the shoes out
against the drum, helping to hold the vehicle in place. Vehicles with rear disc
brakes will still use a smaller drum brake in the center of the
rotor for the emergency brake; they
have proven to be the most trouble free and reliable type of emergency brake.
Brake shoes come in a wide variety of price ranges, from the least expensive
(re-manufactured aftermarket) to the most expensive (new OEM). When
replacing your brake
shoes, cost is always at the back of our minds, but this is really no place
to skimp on quality, these are what stop your vehicle. New OEM (Original Equipment
Manufacturer) shoes are made of higher quality material and will perform better
over the long run than will an aftermarket shoe. Another difference in the shoes
will be how the friction material is attached to the brake shoes; it is either bonded
(glued) or riveted. Less expensive shoes tend to be bonded to the shoe; this process
is less expensive than drilling and riveting, although some shoes are bonded from
the factory due to the thickness of the friction material. Brake shoes tend to last
about twice as long as the
front pads
on a vehicle due to the brake bias (front to rear ratio) and how well they are kept
in adjustment.
When brake shoes begin to wear down, you will notice more travel in the emergency
brake lever (pedal) and possibly a soft brake pedal. The latter of these is due
to the fact that the brake system must displace more fluid to compensate for the
missing friction material before the shoe contacts the drum. Drum brakes incorporate
an automatic adjusting mechanism, unfortunately not may of them work as designed
or they become frozen up do to the extreme heat they endure from the brakes. Some
vehicles have a window or slot in the backing plate where you can access the adjuster
to manually adjust the brakes, if not the wheel and drum must be removed from the
vehicle to access the adjusting mechanism. When manually adjusting brakes, lift
and support the vehicle, spin the wheel while using an adjusting spoon or small
screwdriver to turn the adjuster wheel, adjust the shoes just until you can hear
them rubbing the inside of the drum, but not so tight as to inhibit the wheel from
rolling. If your rear drum brakes begin to grab or “lock-up” it could be due to
over-adjustment or worn shoes contacting too much surface inside the drum. The shoe
shouldn’t contact its entire surface area or they will grab.
If you decide to replace the drum brakes on your vehicle, there are a few specialty
tools that will make the job much easier. Anchor pin tools and spring tools will
keep you from possibly hurting yourself trying to pry them off and on. As with any
vehicle repair, wear the proper safety attire, and avoid breathing the dust created
by the brakes wearing. Another thing to consider is replacement of all of the hardware
in the drum brake assembly (combo kit). Springs can become brittle and lose their
strength when they get hot and then cool, such as with the brakes. If when replacing
your brake shoes, you notice any moisture around the wheel cylinder, it should be
replaced. If the wheel cylinder fails, you will lose part of the braking system
pressure and it may cause an accident. It is also advisable to replace the
wheel cylinders as a set
(both sides) if one is worn the other can’t be far behind.
Early brake shoes were made of an asbestos based material, so breathing the dust
created by them can be hazardous to your health. These materials were phased out
many years ago in favor of safer materials that aren’t as dangerous. Regardless,
breathing brake dust can cause long-term health issues; therefore it is recommended
using a mask when replacing the brake shoes on your vehicle to filter out the fine
particulates.
If further technical assistance is needed, our certified car repair technicians
are ready to
answer your car questions.
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