Importance of Correct Tire Inflation Pressure
The advancement of technology, particularly in measuring vehicle
operating parameters, is progressing toward greater efficiency, reliability,
and cost-effectiveness by reducing fuel consumption and, consequently,
harmful emissions. A critical factor in enhancing tire performance is
selecting the appropriate tire pressure based on vehicle weight, ambient
conditions (such as temperature and external pressure), and usage
patterns. Developments in civil engineering and transportation have
enabled the use of superior materials, fuel blends, and measurement
systems to ensure higher reliability and efficiency.
Tire pressure is a significant factor influencing vehicle safety. It has been
observed that varying tire pressure levels lead to different degrees of tire
deformation, which can impact tire stability and contribute to irregular
tread wear. Figure illustrates tires under varying pressure conditions.
Low tire pressure causes tire deformations from the inside in such a way
that contact with the ground occurs only on the outer surface. Then there
is a danger of the tire warming up quickly (increase of temperature) and
damage its structure, which may lead to shorter tire life. Too high tire
pressure values cause it to contact the ground only in the middle part.
For the over-inflated case, the tyre could sustain damage when riding over
road surface irregularities such as potholes and bumps. Passenger
comfort is also marginally compromised. Increasing the tyre pressure
results in a decrease in tyreroad contact area, resulting in slightly poorer
traction and braking capabilities.
In the third case, the tire pressure is correct. The tread consumption is
regular, which affects the driving comfort and increases the tire life and
shorter braking distances. Correct tire pressure and temperature values
allow for lengthening the life of the tire by 30%.
Rolling Resistance
When a tire rolls on the road, mechanical energy is converted to heat as a
result of the phenomenon referred to as rolling resistance. Effectively, the
tire consumes a portion of the power transmitted to the wheels, thus
leaving less energy available for moving the vehicle forward. Rolling
resistance therefore plays an important part in increasing vehicle fuel
consumption.
Definition of rolling resistance
Most people are familiar with the phenomenon of rolling resistance from
first hand experience. When riding a bicycle or pushing a wheelbarrow
with under-inflated tires, one notices that a fair amount of effort is
required to keep it moving, even at a relatively slow speed. The reason for
this is, of course, that the resistance to rolling increases with reduced tire
pressure. Most people will immediately realize the cause and inflate the
tires to a higher pressure. (It is rather ironic that people do not usually
reach the same conclusion about their car tires - that additional energy is
needed to drive with under-inflated tires - probably because cars have
sufficient power so that the reduction in performance is not so obvious.)
R= (Energy input into a tire – Energy output by tire)/ speed
= Energy lost in tire/speed, W/m/s
The unit of R is watt per meter per second, which is equivalent to N.
Though the unit of R is expressed in terms of N the rolling loss does not
represent ‘force’ but ‘energy/unit distance’. Generally, rolling loss and
rolling resistance are considered equivalent terms and are used
interchangeably. Energy loss in a tire includes hysteresis loss, aerodynamic
drag, friction between tire and road surface and wind resistance.
Hysteresis loss is the major factor and contributes about 90-95% of rolling
loss.
Influence of Tire Pressure on Fuel Consumption
The significance of maintaining proper tire pressure, particularly regarding
rolling resistance and fuel consumption. Measurements reveal that lower
tire pressure increases rolling resistance, requiring more energy from the
engine to overcome it. Consequently, fuel consumption rises, leading to
higher CO2 emissions. Each litre of diesel burned produces at least 2.7 kg
of CO2, a significant contributor to global warming. Driving with underinflated tires not only wastes fuel but also generates unnecessary
emissions and depletes non-renewable resources.
Driving with slightly higher tire pressure than the manufacturer’s
recommendation reduces rolling resistance and fuel consumption.
However, tire pressure impacts other critical factors, including traction,
tire lifespan, stopping distance, and surface stability. Therefore, exceeding
or falling below the recommended pressure is inadvisable.
All rolling resistance measurements in this study were conducted at a
constant speed. At higher speeds, rolling resistance is expected to
increase slightly, though this rise would be proportional across different
tire pressures. Similar trends have been observed in other studies
simulating driving speeds around 70 km/h.
Tyre under-inflation is a more common and serious problem. Reducing
inflation pressure increases a tire's rolling resistance and hurts fuel
economy. Plus, an under-inflated tire flexes more, which leads to
increased and uneven tread wear. The lower tire air pressure will lead to a
larger contact area of the tire tip with the asphalt. Likewise, a greater
contact will increase the rolling resistance, with increasing rolling
resistance it will require a large amount of energy to drive the car with
this the fuel consumed by the engine will also increase.
In conclusion, maintaining the correct tire pressure is essential for
economic, ecological, and safety reasons, warranting regular attention
and upkeep.