Claas has launched a new ‘automatic trailer stretch brake’ option for its Arion range of tractors equipped with CMATIC transmissions.

The manufacturer say the concept stabilises the tractor-trailer combination on slopes and slippery surfaces in order to prevent the risk of jack-knifing alongside including a range of additional features.


Designed for Arion 500/600 series tractors with both a CMATIC transmission and air brakes, the new feature helps relieve the burden on drivers in difficult conditions such as pulling heavy trailers downhill or working with square balers or trailed crop sprayers on slopes.

With four new functions to support the driver, the system automatically activates the trailer’s air brakes as soon as critical thrust forces are exerted on the tractor that could potentially result in the trailer jack-knifing.

The system operates using sensors in the transmission to record engine torque and transmission loads going through the drive train.

The system operates using sensors in the transmission to record engine torque and transmission loads going through the drive train.

Brakes engaged automatically

The driver can increase the braking action of the combination by pulling back the drive lever in auto mode or in stick mode.

This increases deceleration by reducing the transmission ratio and increasing the engine speed to match the forward speed.

For maximum deceleration the air brake engages automatically to reduce the trailer’s ground speed and stretch the tractor-trailer combination.

The automatic trailer-stretch function can also be used with active cruise control speeds up to a maximum 20km/h.

On gentle slopes and with lights loads, the cruise control speed is automatically maintained by activating the pneumatic trailer brakes; on steep slopes and with heavy loads, exceedance of the set cruise control speed is reduced.

This function can be used when working on slopes with square balers or trailed crop sprayers, providing a safety boost. At low operating speeds the thrust when driving downhill is automatically detected and the combination is maintained at the speed predefined by the accelerator pedal.


Claas says the automatic trailer stretch brakes also assist with reversing trailers, forage wagons and balers etc by triggering the braking action as soon as the driver initiates a change in direction using the reversing lever or the button on the CMOTION control lever.

The pulsing action of the brakes helps prevent overheating with automatic braking assistance.

The automatic trailer stretch brake is available from now and can be retrofitted to Arion 500/600 units built from 2021 onwards.