When was the last time you checked the tyre pressure of your car’s tyres?
Tyre pressure tends to be one of the most overlooked aspects of a car. The correct tyre pressure makes a difference to the performance, safety and fuel economy of your car. Instead of buying all sorts of fancy gadgets and fuel additives to improve performance, proper tyre pressure may in fact be the most effective upgrade for your car.
Under-inflated tyres can affect a vehicle’s handling and compromise safety. Here’s why:
Uneven Tyre Wear
Tyre pressure should be checked at least once a month and before long journeys. Car owners who do not regularly check their tyre pressure may find that their tyres are under-inflated, as tyres lose air pressure naturally – about 7-14 kPa per month (3 to 6%). Some drivers may also deliberately drive on lower-than-recommended tyre pressures, thinking that the larger contact area gives them more traction. However, the uneven contact between the tyres and the road will cause excessive wear on the inside and outside edges of the tread. This may even lead to tread separation and a tyre blowout while on the road, which is extremely dangerous.
Increased Rolling Resistance
Because the area of the tyre in contact with the road is larger, the engine has to work harder to overcome the resistance. This increased rolling resistance and friction is bad for the car’s overall fuel efficiency. In fact, tyres under-inflated by 100 psi have increased rolling resistance that leads to around 6% greater fuel consumption.
When tyres are under-inflated, the shoulder areas of the tread wear down faster than the centre, because there is insufficient air pressure to allow the centre of the tread to carry its fair share of weight. Without enough pressure, the centre of the tyre tread may collapse and become very concave, trapping the water rather than allowing it to flow through the tread. The tyres lose grip and the car starts sliding when a thick layer of water gathers between the contact areas of the tyre and the road. Tyre pressures 30% below the recommended pressure sharply increases the risk of aquaplaning. In a tropical country like Singapore where we experience wet weather regularly, under-inflated tyres can pose a great danger to drivers, passengers as well as pedestrians.
Poor Road Holding
With under-inflated tyres, driving and cornering at high speeds is more dangerous. As the tyre sidewalls squirm or flex, steering becomes more unpredictable and less precise. If a bend can be taken at 100 km/h at a tyre pressure of 200 kPa, this speed drops to 87 km/h at 100 kPa, or about 13 km/h less.
Increased Braking Distance
Braking distances may also be increased with under-inflated tyres. According to tests done by Michelin, the distance it takes for a car to brake from 90 km/h to 70 km/h is 40 metres at 200 kPa, but 45 metres at 100 kPa. In the case of an accident, the 5 metres difference can mean life or death.
What Are The Recommended Tyre Pressures For My Car?
There is no standard tyre pressure recommended for all cars, as different tyres have different grip and speed ratings designed to work within a specific weight and air pressure range. The recommended tyre pressures for your car are usually printed on a label on the front door frame or the inside of the petrol flap. The owner’s manual should also include this information.
Tyre pressure should be checked at least once a month, and can be done at any petrol station. However, many Singaporeans do not check their tyre pressure regularly. With a Tyre Pressure Monitoring System (TPMS), your car’s tyre pressures can be monitored in real time from the convenience of your seat. When abnormal or low tyre pressure is detected, the TPMS alerts the driver immediately, avoiding further damage or even tyre blowout while driving.
TPMS is also recommended for run-flat tyres. As these tyres are designed to resist the effects of deflation when punctured, any punctures or leaks may not be obvious to the naked eye. With a TPMS installed, you will be alerted immediately if there is a drop in pressure.
Due to the influence tyre pressure has on vehicle safety and efficiency, it is mandatory for all passenger cars in the United States, European Union and South Korea to be equipped with a TPMS. Several other countries are also expected to implement this regulation. As its increasing popularity demonstrates, the TPMS is a worthwhile investment to ensure optimum tyre pressure, and will go a long way in improving your car’s handling and fuel economy.