Extract of the Conti Tyre Pressure Table
What tyre pressure is correct?
But which air pressure is the right one? It is specified by the vehicle manufacturer and can be found in the documents or in a tyre pressure table. Often it can also be found on a sticker in the car door. If it is 2.5 bar, this is not the absolute pressure, but the pressure relative to the ambient pressure. The latter is about 1 bar, resulting in an absolute tyre pressure of 3.5 bar. But the tyre pressure gauges at gas stations always show the relative air pressure. If you need 2.5 bar, this is also the right pressure for measuring and filling. Check the pressure when the tyre is cold, for example after about 10 km in urban traffic.
Modern cars are equipped with tyre pressure monitoring system (TPMS). Checking the air pressure is not necessary anymore as deviations are communicated electronically via the on-board system. For all new passenger cars the TPMS is required by law. The air pressure is measured by a sensor in each wheel. For the driver it also means additional costs for the sensors on the one hand and on the other hand for changing tyres, which is more expensive now. First and foremost, however, the TPMS will provide more safety for motorists.
Tyre pressure measuring
© blue studios gmbh
It is advisable to check the tyre pressure of the vehicle regularly. So tyre damage can be avoided, because it can be facilitated especially by low air pressure. If you have to refill air every few weeks, you should have the tyre valves checked - they might be defective. Independently, valves will be replaced by a every tyre change - it only takes few seconds. Usually it is about rubber valves, which are also known as "snap-in valves".
Combined with alloy wheels metal valves are used. They are more expensive, but also look better. Make sure that the cap is screwed onto the valve because dirt and dust will get in otherwise - that reduces the life of the tyre valves, which are usually designed for four years.
Have you been already offered filling tyres with gas instead of air? Many shops offer this for a appropriate payment and more and more drivers are wondering: Will that help? Supposedly it saves you checking the air pressure, because nothing can escape. Putting off the rose-colored marketing glasses will show no benefit for the average consumer. But what about tyre gas anyway?
Tyre gas is nitrogen, which volatilised not so fast. Air consists of around 78 per cent of nitrogen, but escapes not much faster from an intact tyre. If a tyre is damaged, tyre gas doesn't help at all. And a damage is usually detected by checking the air pressure - which is therefore also necessary when the tyres are filled with gas.
But there are still advantages in tyre gas, which does not apply to motorists: The oxygen in the air can facilitate a tyre fire or rapid oxidation - but only at very high pressure. It plays a role in racing, for aircraft and heavy transports, but not for cars or motorcycles. So you can save the cost of a tyre gas filling.