A trailer tyre auto inflation system automatically maintains tyre pressure by re-pressurising tyres when they fall below a defined threshold. Unlike TPMS (Tyre Pressure Monitoring Systems), which only provide alerts, these systems actively restore pressure.
This type of system is commonly referred to as TPRS (Tyre Pressure Refill System). It operates continuously to maintain the correct pressure without driver intervention.
Pressure Systems International (PSI) is widely recognised as an early developer of this technology. Similar systems are also offered by other manufacturers, including SAF-Holland under the name Tire Pilot.
How it works
Air is typically drawn from the trailer air supply, most commonly the air suspension system. It passes through a pressure protection valve within a control box, where it is regulated to the required tyre pressure. The control box is set according to tyre manufacturer recommendations and the intended operating conditions.
From the control box, air is distributed to each wheel end. In many designs, the axle beam acts as a pressurised conduit. Where this is not suitable, internal tubing provides the air pathway.
Air is delivered through hoses directly to the tyre valves. If the pressure in any tyre drops below the preset threshold, typically by around 3 psi, the system activates and restores the correct pressure automatically.
The system operates both when the trailer is stationary and when it is in motion.
Benefits of tyre auto inflation systems
- Maintains consistent and optimised tyre pressure
- Extends tyre life and reduces replacement frequency
- Helps reduce fuel consumption and associated emissions
- Reduces the risk of running under-inflated tyres
- Supports safer operation
- Reduces downtime linked to tyre-related issues
Industry adoption and system availability
- Pressure Systems International (PSI) was established in 1993
- More than 1.5 million systems are reported to be in operation worldwide
- Systems are compatible with a wide range of trailer axle configurations
- Multiple manufacturers supply equivalent systems under different brand names
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