Sooner or later the wheels of any car have to be inflated. To get the correct pressure in the tire can be difficult. Help in this case can be a manometer. Here is just one little problem. Most of them are not able to correctly show the pressure in the wheels of the vehicle. The culprit is not the pressure gauge itself, but the spool, which distorts the pressure reading.
If a reference gauge is also installed in front of the compressor with a built-in pressure gauge when inflating the wheel, an unpleasant surprise awaits the motorist. It is likely that the pressure reading on the reference pressure gauge will be noticeably higher than that of the compressor. And that’s assuming that compressor pressure gauges artificially inflate the reading for safety reasons! Usually in the wheel is lost 0.2-0.4 bar of pressure. Many motorists naively believe that the problem is in the measuring equipment, but in fact it is not.
In the vast majority of cases, it’s not the gauges that are to blame, but the wheel valves. Different models have different degrees of distortion of readings. Usually it is somewhere in the range of 0.2-0.6 bar. The difference in readings between pressure gauges directly depends on the degree of displacement of the spool rod when the compressor hose is put on it. Also, the readings are distorted by the resistance that inevitably occurs when the air pressure increases. However, as the pressure in the wheel increases, the error gradually decreases by reducing the resistance. As a result, the readings become more accurate. It is only when the pump has reached its maximum permissible pressure that the error disappears completely.
What are the practical tips that follow from all this? First, you need to be careful to ensure that the compressor hose is properly and evenly connected to the valve. Even insignificant misalignment significantly distorts the information, which is presented to a motorist by a built-in pressure gauge. Secondly, it is worth remembering about distortion of readings from resistance. Therefore, it would not be superfluous to inflate the wheel a little bit stronger than it is supposed to be. About 0.2-0.3 bar over the “norm” will be enough.