Max. pressure
The maximum pressure provided by the pump or compressor — in other words, the highest tyre pressure that can be achieved using this unit.
In most models, this figure is
from 2.5 to 10 atm, and in mechanical pumps (manual and foot, see "Type") pressure of more than 10 atm is practically not found at all. This is due to the fact that even for heavy trucks, the optimal tyre pressure is usually about 5 – 9 atm (depending on a number of parameters — there are special formulas and tables for calculations); and in passenger car tyres, a pressure of more than 2.5 atm is extremely rarely used. However, there are compressors with higher pressure parameters —
11 – 15 atm,
16 – 20 atm and even
higher. The meaning of such characteristics is mainly in the "power reserve": a higher working pressure contributes to faster pumping. However, be careful not to over-inflate the tyre and damage it.
Performance
The capacity of the compressor (see "Type") is the maximum amount of air that it can pump into the tyre in a minute.
Higher performance reduces the time required to inflate the wheel; on the other hand, this parameter directly affects the dimensions, weight, power consumption and price of the compressor. So it is worth choosing according to performance, taking into account real needs. So, for a “duty” tyre inflation in a passenger car, a compressor with a low operating speed is quite enough — up to
20 L / min inclusive. And if the speed of full pumping is also important for you (for example, after replacing the rubber) — you can choose a unit for
21 – 40 L / min. In turn, models with more solid characteristics —
41 – 60 L / min and
more — are intended mainly for heavy equipment like SUVs, trucks, tractors, etc.
Separately, it should be noted that this parameter is NOT suitable for calculating the exact inflation time (even if the exact volume of air in the wheel is known). The fact is that the actual performance of the compressor is always lower than the claimed one: the figures in the characteristics are indicated for free air outlet, and when pumping the wheels, the pumping speed will inevitably be lower due to the resistance of the nipple.
Power
Rated power consumed by the compressor during operation.
This parameter primarily affects the features of connecting the unit to the on-board network through the cigarette lighter socket. Such a socket has restrictions on load power, and these restrictions are different for different cars; and even in the same car, different connectors — the cigarette lighter itself and a separate socket of the same format — can differ in allowable power. However, most of these connectors can easily cope with units with a power of up to 100 – 120 W; but if you get a more powerful compressor, you should clarify the possibility of using it with a specific cigarette lighter (the easiest way to do this is according to the documentation for the car). If the device is planned to be powered through "crocodiles" or from a 230 V socket (see "Connection"), you can not pay much attention to the power consumption.
Also, more powerful compressors, usually, have a greater capacity and/or maximum pressure, but there is no strict relationship here.
Hose length
The length of the hose through which air is pumped into the tyre. The larger it is, the more convenient the device is to use. But it is rare that the compressor is left far from the wheel, especially if a pressure gauge is placed on the device, which must be periodically checked. For domestic use in cars, a one and a half metre long hose is enough. Powerful and performant models can be equipped with a hose of 7 metres or more, but these are more solutions for commercial use in car services.
