Air-brake coils
In the pneumatic connections between truck and trailer, the air spiral hose fulfils a technically demanding role. It transfers compressed air between vehicle units while continuously coping with mechanical stress, chemical exposure and repetitive movement. When selecting a suitable compressed air coil for trailer and truck applications, material properties and connection standards are the determining factors.
The most widely used configuration in professional road transport is the PUR air spiral with M16x1.5 connection. PUR refers to polyurethane, a material group with proven resistance to oils, greases and abrasive conditions. In a workshop environment or during daily road use, air spiral hoses are regularly exposed to contaminants that would cause accelerated degradation in less resistant materials. Polyurethane maintains its elasticity across a wide temperature range, which is essential for outdoor applications where temperatures can vary significantly between seasons and operating conditions.
The M16x1.5 metric threaded connection is a standardised fitting widely used across the European truck and trailer industry. The designation M16x1.5 refers to a metric external thread with a nominal diameter of 16 millimetres and a pitch of 1.5 millimetres. This specification determines mechanical compatibility with the connection points on the vehicle and the fittings within the pneumatic circuit. A correct connection in accordance with this standard is required for a leak-free and durable joint under working pressure.
Within the range of air spiral hoses for truck and trailer, two colour codings are common: yellow and red. Colour coding has a functional significance in pneumatic vehicle technology. Yellow is traditionally associated with the service brake air line and red with the emergency brake line, although this can vary by configuration and market. Consistent use of the correct colour reduces the risk of misconnection during installation and maintenance, contributing to vehicle safety.
A relevant variant is the air spiral hose with an integrated spring at the connection points. The spring provides additional mechanical support at the locations where the hose is most exposed to bending stress. At the transition between the connector and the spiral body, there is an elevated risk of fatigue failure due to repeated bending. The spring guard absorbs and distributes these bending forces, extending the service life of the compressed air coil. For applications involving intensive coupling and uncoupling, such as daily trailer swaps, this version is technically justified.
A working length of 4 metres is a standard dimension that provides sufficient freedom of movement for most truck and trailer combinations. In coil form, the hose compensates for the change in distance between coupling points during manoeuvring, without risk of overextension or pinching. The coiled form is not a decorative feature but a functional design that increases the effective length of the hose while keeping the resting length compact.
For workshops, trailer manufacturers and body builders working with pneumatic vehicle systems, a thorough understanding of the material and connection specifications of air spiral hoses is essential. The combination of a PUR air spiral M16 connection, the standardised M16x1.5 thread and availability in the recognised colour codings makes this product group applicable across a broad range of situations in heavy road transport. Whether for new trailer construction, replacement of worn hoses or fleet maintenance, the technical characteristics of the air spiral hose determine the reliability of the pneumatic connection between truck and trailer.