Traction Control Systems
What is traction?
Traction is the grip that your car’s tires have on the road, which is needed to
accelerate, turn and brake. If your car, or more specifically, your tires have
little or no grip; your car will not accelerate, turn or brake and will skid.
Therefore, sufficient traction is an extremely important part of the performance
and safety of your vehicle. Traction control devices in the car reduce the
loss of grip so your tires will have traction to accelerate, turn and brake.
The most common and well-known traction control device is the Anti-Lock Brake
System (ABS), which is described in greater detail
here.
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Traction Control
Traction Control is used to prevent the drive wheels from losing grip when accelerating.
Spinning tires during hard acceleration may be dramatic, but it is the slowest way
to get to your desired speed. Using the car’s ABS speed sensors at the wheels,
the Traction Control computer compares the drive wheel’s speed to the car’s
road speed. If there is a loss of grip event during acceleration, there are a
number of ways that the Traction Control slows the drive wheels so they can
regain grip. The most common method is to use the braking system. When the
drive wheels lose grip, the ABS computer can apply the brake to the wheel
that has lost grip to slow it down so it can regain grip. Another method
for slowing the slipping wheels is to reduce the amount of power applied to them.
The computer will electronically modify the amount of fuel entering the engine
and/or use the transmission to slow the drive wheels so they can regain grip.
Because Traction Control increases traction by reducing either engine power or
applying the brakes, most drag racers turn off their Traction Control Systems
(if possible) when drag racing. This allows the vehicle to use all of its
available power to move the vehicle forward during the initial launch. A
careful launch with minimal wheel spin will lead to faster times that just
leaving Traction Control on and stomping the gas. In normal driving,
however, you should always leave it on.
Stability Control
The latest traction control technology introduced to motor vehicles is
Stability Control. While ABS and Traction Control help manage the grip of
the tires for braking and accelerating, Stability Control helps prevent a
car from sliding sideways. Using the same components in the ABS and Traction
Control systems, Stability Control adds other sensors. These include a
steering wheel angle sensor and yaw rate sensor. Yaw is defined as
"the movement of an object turning on its vertical axis”. Stability Control
is used to manage the amount of understeer a vehicle will exhibit if the
driver used too much steering or entering a turn too fast. It will also
manage oversteer if the driver uses too much or too little throttle while
turning. Much like the other technologies of traction control, Stability
Control will apply the brakes and/or throttle to a wheel or a number of wheels,
independently, so the driver can regain control.
Modern vehicles, that offer traction control devices, perform a self-test
on the ABS, Traction Control and Stability Control computer(s). If there
is an error encountered in any of these systems when starting or
while driving, an error light will steadily illuminate in the instrument
cluster of the vehicle. During this time, one or more of these traction
control devices will be unavailable and you should know how to maintain
vehicle control if these aids are unavailable.
Since Stability Control is used for maintaining control in turns, most racers
leave it on all the time, even for drag racing.
