By Denna Bowman
A staggering 71% of European motorists are driving on under-inflated tyres, wasting 2 billion litres of fuel a year and adding 4.8 million tonnes of CO2 emissions into the environment, according to a survey by a leading tyres manufacturer.
Bridgestone, which checked out the tyres on 38,000 cars in 9 European countries in 2010, calculates that this habit is leading to the equivalent of 2 billion tonnes of wasted fuel a year. For the environment this means 4.8 million tonnes of additional and unnecessary CO2 emissions annually – the equivalent of 1.8 g/km for every car on the road.
The tyre safety checks were carried out at shopping centres and public car parks as part of the Japanese company’s regular tyre safety campaign activities.
Analysis of these test results show that 7.5% of motorists are driving on seriously under-inflated tyres (at least 0.5 bar below recommended pressure) and 0.5% are putting their safety at high risk by driving on severely under-inflated tyres (at least 0.75 bar below recommended pressure).
Almost 12% of tyres on the road are also worn down below the legal minimum of 1.6 mm tread depth, while around 2% of inspected tyres are both severely worn and severely under inflated.
The results suggest that many motorists are unaware that a tyre loses pressure naturally over time, like a balloon, and that driving on incorrect pressure is not only dangerous but also wastes fuel and adds significantly to CO2 emissions.
This is because inflation pressure strongly influences tyre rolling resistance, which is itself a key factor in determining vehicle fuel consumption. Depending on the type of road and driving style, rolling resistance represents 18% to 26% of the total force on a vehicle. Since low inflation increases rolling resistance, it has a direct effect on vehicle fuel efficiency and emissions.
Driving on under-inflated tyres and insufficient tread depth is doubly dangerous. The loss of vehicle handling control and increase in vehicle drift rise sharply as tyre pressure is reduced.
Low tyre pressure also has an extremely negative effect on tyre durability, due to excessive shear stress in the tyre shoulder and heat build-up from sidewall bending. Motorists identified with seriously low tyre pressure face possible tyre failure due to these factors.
Tyres worn down below the legal tread-depth limit represent an immediate safety risk. For a car travelling on tyres with a tread depth below 1.6 mm, the speed at which hydroplaning starts is reduced by up to 40%.