Trailer operation: A real workhorse

Jun 24, 2019
Stuttgart/Salt Lake City

One of the strongest reasons for purchasing an SUV is its great suitability for towing a trailer. All-wheel drive and a transmission ratio configured for pulling power allow high towing capacities, while the height, width and relatively high vehicle weight improve the driving stability of the combination. The new GLS is designed to do all this even better. And it is aided in this by Trailer Manoeuvring Assist.

Doing things better already begins with the trailer coupling. A fully electric version of this is available for the European market. Using buttons in the liftgate or the driver's door – protected against operating errors – the ball neck including the socket for the trailer electrics swings up from under the vehicle and automatically engages in its operating position. After its use, it retracts back into its rest position behind the bumper equally effortlessly.

Apart from positioning the button outside the reach of children, the trailer hitch also has an automatic reversing function similar to the power windows. To prevent operating errors due to snagged items of luggage, a pull switch is used instead of a push-button.

Fix4Bike: new accommodation for bike racks

A special feature is also provided for those who do not use the coupling to tow a trailer, but e.g. to carry bicycles: the trailer coupling has two extra bolts on the ball neck to carry a suitable cycle rack in safety, This design allows the load-carrying capacity to be increased to 100 kg and four cycles - particularly useful in the case of e-bikes, which could previously only be carried to a limited extent. The carrier is particularly easy to install, and also protects the rear bumper against damage. Previous racks can still be used, although these are limited to carrying three bikes and 75 kg.

Trailer Manoeuvring Assist

In conjunction with the Parking package, attaching a trailer is convenient even without outside help: aiming for the tow bar is done via the reversing camera. To this end, it has a zoom mode to precisely show the position of the tow bar and ball neck in relation to each other at close range. Once the combination Is hitched, briefly driving straight ahead calibrates Trailer Manoeuvring Assist with its articulation angle protection. This makes manoeuvring with a trailer easy even for the inexperienced.

Trailer Manoeuvring Assist controls the steering angle of the towing vehicle automatically up to a limited speed. An articulation angle sensor in the ball neck of the trailer coupling supplies the necessary information.

Four cameras (at the front in the radiator grille, at the rear in the tailgate handle and in both exterior mirror housings) monitor the vehicle's surroundings. It is not only their respective images that can be displayed, as a combination of them also generates a virtual bird's-eye view of the vehicle. When reversing with a trailer, a wide-angle view of the trailer and a symbolic representation of the combination are displayed. The driver can then select the articulation angle at which the combination is to reverse. The steering is automatically influenced to maintain this angle. When the trailer has moved in the right direction and is to continue reversing in a straight line, the driver presses the "Straighten up" icon in the touchscreen and the steering automatically performs the manoeuvre. Skilfully towed by the GLS, the trailer moves in a dead straight line.

When a trailer has been hitched up and connected, Trailer Manoeuvring Assist is activated when at standstill by engaging reverse gear and pressing the Parking button to the left of the touchpad in the centre console, and works at speeds up to 8 km/h and even on uphill gradients up to 15 %. Trailer Manoeuvring Assist can be intuitively operated via the MBUX (Mercedes-Benz User Experience) infotainment system: using the media display or the touchpad in the centre console, the driver only needs to select the required manoeuvre (indicating the direction by entering the desired articulation angle or selecting the "Straighten up" function). The manoeuvre can then be monitored from different camera angles. Dynamic guide lines show the trajectory, vehicle width and distance from recognised objects.

If the articulation angle exceeds 5 degrees, the speed of reverse travel is reduced to 5 km/h. And if the driver turns the steering wheel or the articulation angle threatens to become too large, the vehicle automatically stops. Trailer Manoeuvring Assist particularly ensures additional safety for drivers who only occasionally manoeuvre with a trailer in situations that could quickly lead to stress.

A real workhorse: up to 3500 kg towing capacity

The new GLS is however also an excellent towing vehicle for driving a solid straight line. It will effortlessly manage braked trailers with a total weight of up to 3500 kg and tongue weights of up to 140 kg. ESP® features a trailer stabilisation function that recognises any oscillating tendency by the combination and counters this with specific braking intervention, right up to full braking of the combination. When the trailer has ceased to oscillate, the system ends its intervention.

The control systems of AIRMATIC and E-ACTIVE BODY CONTROL also adapt automatically to an attached trailer and control the suspension level and damping accordingly. Assistance systems that are not compatible with trailer operation, e.g. Active Parking Assist, are likewise automatically deactivated, though naturally with a corresponding warning for the driver in the cockpit display.