The area that holds our car on the road is just four palms in size. It is all the more important that the tires have the right pressure. Because even the densest tire loses some air over time. New cars have air pressure control systems, but their security is deceptive (see box).
With older cars it is mandatory anyway: ideally every fortnight, but at least monthly and absolutely after the seasonal tire change and before long journeys, you should invest five minutes at the gas station to check the pressure.
Where is the target pressure?
The target pressure can be found in the car’s operating instructions and almost always on a sticker – either in the fuel filler flap or in a door frame (usually in the rear door pillar of the open driver’s door). This is the minimum pressure for cold tires! So if you don’t just drive around the corner to the gas station in town, but have warmed your tires ten kilometers away, you have to calculate differently.
Better to have 0.3 bar more
The most important rule of thumb: A little more pressure never hurts, but too little with a guarantee. About 0.3 bar above the specified target is never wrong and even saves fuel. Just 0.3 bar too little harms safety, increases fuel consumption and can ultimately destroy the tire because it overheats if too little pressure is applied.
Tip: Regardless of the route to the petrol station, add a flat rate of 0.3 bar, for example, if the target pressure is 2.0 bar, then fill in 2.3 bar. If it is very hot outside, it can be 0.4 too much. So you are on the safe side.
Because: The tire pressure also fluctuates with the outside temperature (every ten degrees more 0.1 bar more). If you pull up the winter tires at 20 degrees and only fill in the target pressure, you have 0.3 bar too little at minus 10 degrees. If you stick to the plus 0.3 rule, this usually covers fluctuations.
Tire pressure monitoring systems have been mandatory for new cars since November 2014. But the supposed security is deceptive. Why? Only active systems (show pressure in bar) measure the pressure and are also quite accurate. But they can also measure incorrectly at times. And the cheaper passive systems (only warning lights) measure wheel speeds. You can calculate sudden pressure loss on one wheel from this – but the normal, slow loss on all wheels only too late!
In a study by the German Road Safety Council (DVR), 37 percent of the cars without a control system had the wrong pressure – and 33 percent of the cars that have a system! One reason: Especially at low outside temperatures, false alarms often occur because the pressure drops with the outside temperature. This then quickly leads to the warnings no longer being taken seriously.
So please continue to check manually. Important: After changing the tires or correcting the pressure, almost all cars require a system reset – see operating instructions.
How to check air pressure
First unscrew the small black dirt protection rubber cap from the valve. Now get the air pressure tester. There are two types at petrol stations: fixed to the wall with a spiral hose that can be pulled out and portable with a short hose. The scale shows the pressure, the plus and minus buttons increase or decrease it.
Put the test tube straight on until it is tight (no air can be heard to escape). Check the display. If correct – done. If too little: Press the plus button only briefly (intermittently) and pay attention to the scale. If the desired pressure is there, pull off the measuring tube, put the black rubber cap on the valve and move on to the next wheel. Important: Check the spare wheel from time to time, at least before traveling.
Pay attention to warning signs
Otherwise: Pay attention to warning signs. Too little pressure can only be seen when the tire is practically empty! If the car pulls to the side when braking, pushes hard over the front tires in turns or suddenly makes “creaky” noises when maneuvering, it doesn’t have to be, but there may be too little pressure. If a tire suddenly hops or clicks, there is a high risk of punctures!