To inflate and seat tractor tyres, what you need most is air volume and a good reserve in the receiver, more than high pressure. A compressor delivering about 1 m³/min on a 300 L receiver, such as the 12.5 bar E 75 HP, inflates a large rear tyre in a few minutes and keeps the reserve needed for bead seating.
Inflation is only part of the work in an agricultural machinery workshop. This article focuses on one specific case: large agricultural tyres.
How much air does a tractor tyre take?
The calculation fits on one line: air to supply = internal volume of the tyre × pressure rise (in bar).
Agricultural tyres run at low pressure: it depends on load, speed and use, and is given in the tyre maker's tables. The volume, on the other hand, is large. For the example, take a rear tyre with an internal volume of about 1,000 litres and a working pressure of 1.6 bar. These are assumptions: replace them with your own tyres' values.
- Full inflation, from 0 to 1.6 bar: 1,000 × 1.6 = 1,600 litres of air.
- Top-up, from 1.0 to 1.6 bar: 1,000 × 0.6 = 600 litres of air.
- Time with a 1,050 l/min compressor: about 1.5 minutes for full inflation, under a minute for the top-up.
In practice, allow longer: the valve and the inflator restrict the flow. Removing the valve core during inflation speeds things up noticeably.
Bead seating is a question of reserve
To seat a tyre, the bead must snap against the rim in one go. That takes a high flow for a few seconds, more than the compressor produces continuously. The receiver supplies it.
Example: a 300 L receiver charged to 12.5 bar and allowed to fall to 8 bar releases 300 × 4.5 = 1,350 litres of air in a very short time. That reserve, more than the motor, is what makes the difference when seating a bead. If you often seat large tyres, an extra air receiver near the tyre bay increases the reserve. The air receiver size calculator helps you size it.
Which compressor?
- Workshop with a fixed tyre bay: the E 75 HP. Two-stage piston compressor, 12.5 bar, 1.05 m³/min, 300 L receiver, on wheels. The high pressure fills the receiver with a large reserve. It suits intermittent use: inflate, seat, then let it rest.
- Inflating in the yard or on the machinery park: the M 75. Electric mobile screw compressor, 1.0 m³/min at 10 bar, 180 L receiver, on wheels. You take it to the tractor instead of dragging a long hose. It needs a 380 V three-phase socket where you use it.
- Dealership where air runs all day: the K 75. 4-in-1 screw compressor with a 420 L receiver, dryer and filtration. 1.1 m³/min at 8 bar, or 0.8 m³/min in the 13 bar version. It inflates tyres while also supplying the workshop's impact wrenches and blow guns.
If you fit tyres in volume, for several types of vehicle, see also our page on tyre centres.
Safety and tyre bay pitfalls
- Never exceed the maximum bead seating pressure stated by the tyre maker. A 12.5 bar compressor can go well beyond it: fit a regulator at the tyre bay.
- Stay out of the tyre's path during bead seating. Use a clip-on chuck, a long enough hose and a remote gauge.
- Check pressure cold, with an accurate gauge. At low pressure, a few tenths of a bar matter.
- Drain the receiver. Condensate ends up in the tyre and rusts the rim. Drain daily, or fit an automatic drain: see our article on water in compressed air.
- Protect the compressor from frost in a poorly heated workshop in winter.
Describe your workshop in the configurator, or send us your tyre sizes and other tools with a quote request.
For your trade: Compressor for agricultural machinery workshops.