An automobile relies on its brakes for safe and effective
stopping, whether traveling at highway speeds or simply backing out of your
driveway. Unfortunately, your braking system may eventually develop problems as
the result of heavy use. Many such problems put you and your car at risk of
danger.
One of the most frequently encountered braking issues goes
by the name of brake drag. Brake drag occurs when one or more of your brakes
don't fully release when you take your foot of the pedal. Brake drag may stem
from a variety of underlying mechanical issues. This article takes a closer
look at three common culprits.
1. Excessive Push Rod Length
The brake system in your car contains numerous components,
each of which plays a distinct role in braking. One of the first components to
engage goes by the name of the push rod. The push rod connects to your brake
pedal, and acts to transmit force from your foot to your brakes.
More specifically, when you depress the pedal, the push rod
transfers force to the master cylinder. This component then releases the
hydraulic fluid necessary for braking. The length of the push rod plays a
critical role in providing accurate, responsive results. If too short, your
brakes won't engage as quickly as they should.
An overly long push rod, on the other hand, leads to brake
drag. This excessive length prevents the master cylinder from relaxing entirely
when you release the brakes. As a result, hydraulic force continues to act on
your brakes, keeping them pressed against the rotors on your wheels.
Ideally, the push rod should be neither too short nor too
long. Mechanics usually allow a small amount of free play. A small gap between
the push rod and the master cylinder prevents brake drag, while avoiding the
issue of unresponsive brakes. A mechanic can measure the exact amount of play
before your brake engages, and make adjustments as necessary.
2. Faulty Caliper Piston
When you apply your brakes, your brake pads press against
your wheel rotors. This contact generates friction which slows your car. Your
brake pads attach to a component known as the brake caliper, which moves them
against the rotor each time you press your brake pedal.
Calipers close and release according to the flow of
hydraulic fluid. The caliper on each of your four wheels has its own dedicated
piston, which is used to transfer hydraulic force into the mechanical movement
of the caliper.
If a caliper piston develops problems, it may no longer
regulate caliper movement correctly. Hydraulic fluid often escapes around a
damaged piston. In that case, the caliper may not release when you take your
foot off of the brake pedal. Unlike other sources of brake drag, a faulty
caliper piston only creates drag in one wheel.
3. Caliper Misalignment
To prevent brake drag, a caliper must remain in correct
alignment relative to the rotor. Over time, a caliper may come out of
alignment. If the issue grows severe enough, one of the brake pads may remain
in contact with the rotor surface at all times.
Numerous factors may play into caliper misalignment. The
problem often occurs as the result of a collision. Even a relatively small bump
— accidentally popping a curb, say — can bend the mounting brackets used to
hold a caliper in place. Alternately, misalignment may stem from rotors or pads
that have become excessively warped as the result of overheating.
A trained mechanic can quickly identify a misaligned caliper
through a visual inspection of your brakes. They may also use a special tool to
measure the distance between each of your brake pads and the rotor. Using this
information, the technician can then re-center the caliper to provide accurate
results.
For more information about what it takes to keep brake drag
from negatively affecting your vehicle's performance, please contact
the
tire and auto repair pros at Radial Tire Service.
