A car tyre inflator uses about 100 l/min at 6.3 bar, a truck tyre inflator about 150 l/min at 9 bar, as a guide. The flow is low: pressure is what decides. The compressor must deliver at least 1 bar more than the highest pressure you need in the tyre, so 10 bar or more as soon as you inflate truck tyres.
The inflator is the most common tool in a tyre centre and in a garage. This article answers one question: what does it ask of the compressor?
Why pressure matters more than flow
Air only flows into the tyre if the network pressure is higher than the tyre pressure. The smaller the gap, the slower inflation becomes towards the end. Two consequences:
- For a car tyre, inflated to a few bar, a network at 6 or 7 bar is enough for inflation. It is the tyre changer, at 8 bar, that usually sets the garage pressure.
- For a truck tyre, inflated to around 9 bar depending on load, the inflator needs 9 bar at its inlet. Adding about 1 bar of losses in the hoses, the compressor must deliver 10 bar.
That is the rule our configurator applies: pressure of the most demanding tool, plus 1 bar.
How much air does it take to inflate a tyre?
The calculation: air to supply = internal volume of the tyre × pressure rise in bar. The volumes below are example assumptions: replace them with those of your tyres.
Car tyre, internal volume of about 30 litres:
- Top-up from 2.0 to 2.5 bar: 30 × 0.5 = 15 litres of air.
- Full inflation from 0 to 2.5 bar: 30 × 2.5 = 75 litres of air.
- With a 100 l/min inflator: under a minute, even for a full inflation.
Truck tyre, internal volume of about 150 litres:
- Top-up from 8 to 9 bar: 150 × 1 = 150 litres of air.
- Full inflation from 0 to 9 bar: 150 × 9 = 1,350 litres of air.
- With a 150 l/min inflator: about 9 minutes for a full inflation, often more because flow falls as you approach the final pressure.
Fully inflating a truck tyre is therefore real air consumption. The receiver supplies part of it, the compressor the rest. Our article on how to calculate compressor pressure explains the link between pressure and air volume.
Which compressor for your use?
Car tyre inflation in a garage. The inflator does not size the compressor: the impact wrench and the tyre changer do. Plan at least 9 bar at the compressor if a tyre changer is connected.
Truck tyre inflation at a fixed station: the K 75 in 10 or 13 bar. 4-in-1 screw compressor, 0.95 m³/min at 10 bar or 0.8 m³/min at 13 bar, 420 L receiver, built-in dryer. It inflates truck tyres and supplies the wrenches and blow guns at the same time.
Truck tyre inflation in bursts: the E 75 HP. Two-stage piston compressor, 12.5 bar, 1.05 m³/min, 300 L receiver. Example: from 12.5 to 10 bar, its receiver releases 300 × 2.5 = 750 litres of air, enough for several truck tyre top-ups without waiting for the motor.
Inflation in the yard or on the fleet: the M 75. Electric mobile screw compressor, 1.0 m³/min at 10 bar, 180 L receiver, on wheels. You take it to the vehicle instead of dragging a long hose. It needs a 380 V three-phase socket where you use it.
For very large agricultural tyres, see our article on tractor tyre inflation.
Inflation pitfalls
An inaccurate gauge. An inflator that reads 0.2 bar too high under-inflates every tyre in the workshop. Have the inflator gauge checked regularly, and inflate cold.
An automatic inflator with too little supply. A preset inflator has a minimum inlet pressure stated in its manual. Below it, it does not reach the setpoint or hesitates at the end of the cycle.
Water in the tyre. Without draining, water from the receiver goes into the tyre and rusts the rim. Drain every day or fit an automatic condensate drain. A 4-in-1 compressor dries the air before the network.
The hose at an outdoor station. A long, narrow hose between the outlet and the tyre slows inflation, especially for trucks. Keep an adequate bore and a connection hose rated for the pressure.
Safety. A compressor at 12.5 or 13 bar exceeds the pressure many tyres allow. Fit a pressure regulator at the inflation station and stay out of line with the wheel.
List your inflators and other tools in the configurator, or tell us which tyres you inflate in a quote request.
For your trade: Compressor for tyre centres.