Munich. High fuel prices have been a drain on holiday savings for years. But one of the most effective counter-measures is completely free of charge: air for vehicle tyres. The right tyre pressure is also an important safety factor. Here are TÜV SÜD’s tips on tyre pressure.
Every year, insufficient tyre pressure causes Europe’s car drivers to waste over three billion litres of fuel, worth five billion euros. When tyre pressure is too low, rolling resistance – which accounts for 18 to 26 per cent of fuel consumption – increases dramatically. In addition, points out Jürgen Wolz from TÜV SÜD, "Low tyre pressure causes significantly higher tyre wear."
Read before inflating: The manufacturer's tyre pressure specifications are given in the car manual and the sticker inside the fuel tank flap or door. As almost all cars can be driven with a range of tyre dimensions, different pressures are often given for the various tyre sizes, which drivers must be sure to observe. A few car manufacturers provide tyre pressure information in kilopascal (kPa), an uncommon unit albeit correct in terms of physics. Conversion into the far more commonly used bar is simple: 100 kPa equal one bar.
Never too little – when in doubt, more is better: Do not undercut the vehicle manufacturer's specifications. Even a shortfall of 0.2 bar will account for up to five per cent higher fuel consumption in city traffic, while 0.5 bar can cost an extra litre per 100 kilometres and may also be a safety hazard at higher speeds. But manufacturers' figures are generally a “comfortable” value and 0.2 or 0.3 bar more will definitely do no harm. Pressure which is much higher than the specifications, however, will impact negatively on driving characteristics and cause uneven wear on the tyres.
Be cool when checking: “Tyre pressure is always given for cold tyres”, advises Wolz. Even trips of less than ten kilometres will cause tyres to heat up. Because of this, do not let air out of the tyres at this point.
More speed, more pressure: For longer motorway trips, TÜV SÜD recommends tyre pressure that is 0.3 bar above the general specification. However, full load pressure is by no means a blanket recommendation for driving at high speeds. Full load pressure is calculated on the basis of the vehicle load; while tyre pressure of almost three bar is recommended for larger estate cars, it would be unsuitable for unloaded vehicles even for motorway driving.
Load up, then top up:Drivers planning to pack their car to the roof or use all available seat space for a longer journey must increase their tyre pressure. Return the pressure to normal – not forgetting the “cold tyres” rule – after the trip!
Air, not gas: Garages now offer special gases for tyres, claiming advantages for them which are not borne out by the laws of physics. Drivers are better off saving their money; the tyre industry and TÜV SÜD agree that air is quite sufficient. And if you plan on quickly topping up your tyres to full load pressure, fuel stations only have air on offer in any case.
Tighten those screws: Valve caps are not there for decoration, but act as covers and protect valves from dirt that might otherwise interfere with the functioning of the valve by causing loss of air.