Importance of Proper Tire Inflation Pressure
A tire is
a pneumatic system, which supports a vehicle’s load. It does this by
using a compressed gas (usually air) inside to create tension in the
carcass plies. It’s important to realize that a tire carcass has a
high-tension strength, but has little or no compression strength. It’s the air pressure that creates tension in the carcass and allows the tire to function as a load-carrying device.
inflation is so important. In an inflated, but unloaded tire, the cords
pull equally on the bead wire all around the tire. When a tire is
loaded, the tension in the cords between the rim and the ground is
balanced or relieved. The tension in other cords is not changed.
Therefore, the cords opposite the ground pull upwards on the bead. This
is the mechanism that transmits the pressure from the ground to the rim.
addition, a tire must transmit handling (acceleration, braking,
cornering) to the road. Cornering forces are transmitted to the rim in
a similar manner to load. Acceleration and braking forces rely on the
friction between the rim and the bead. Inflation pressure also supplies
the clamping force, which creates friction.A
tire also acts as a spring between the rim and the road. This spring
characteristic is very important to the vehicle’s ride. Too high an
inflation pressure causes the tire to transmit shock loads to the
suspension and reduces a tire's ability to withstand road impacts. Too
low an inflation pressure reduces a tire's ability to support the
vehicle's load and transmit cornering, braking and acceleration forces.
can cause many tire-related problems. Since a tire’s load capacity is
largely determined by its inflation pressure, under-inflation results
in an overloaded tire. An under-inflated tire operates at high
deflection resulting in decreased fuel economy, sluggish handling and
may result in excessive mechanical flexing and heat buildup leading to
catastrophic tire failure.
inflation is especially significant to the endurance and performance of
radial performance tires. For example, because of a performance
radial’s aspect ratio and design, it may not be possible to look at a
radial tire and actually see under-inflation of 5 psi. However,
under-inflation of 5 psi can reduce a performance tire's tread life by
25%. A typical tire may also lose 1 to 2 psi a month, if not checked
Air pressure is affected by temperature. The air under pressure in a tire is no exception. Typically, an inflation pressure can change by 1 psi for every 10 degrees Fahrenheit of temperature change. Higher temperature means increased pressure.
example, if a tire is inflated to 35 psi on an 80°F July day, it could
have an inflation pressure of 23 psi on a 20°F day six months later in
January. This represents a normal loss of 6 psi over the six months and
an additional loss of 6 psi due to the 60°F temperature change. At 23
psi, this tire is severely under-inflated.All
tire makers recommend that consumers check their tire inflation
pressure at least once each week, and as often as possible when tires
are cold (ambient air temperature and if the vehicle has not been
driven for several hours).
inflation loss (more than 2 psi per week), visible damage and irregular
wear, or tires experiencing severe impacts, vibration, or pulling
require removal along with an expert inspection of tire and rim to determine
reparability or the need for replacement. Damaged tires may fail
suddenly or burst upon re-inflation, resulting in serious injury.
Article by Tire Review Magazine.