Mercedes-Benz GLK-Class: Trailer towing

Notes on towing a trailer

Important safety notes

WARNING

When towing a trailer, incorrect equipment and driving style could cause you to lose control of the vehicle.

Towing incorrectly or not observing this Operator's Manual could lead to damage to the vehicle and/or serious injuries. Observe the following guidelines to ensure safe trailer towing.

Contact a Mercedes-Benz Center if you need further explanation of the information contained in this Operator's Manual.

WARNING

When backing up the vehicle towards the trailer, make sure there is nobody between the trailer and the vehicle.

Couple and uncouple the trailer carefully. If you do not couple the trailer to the towing vehicle correctly, the trailer could become detached.

Make sure that the following values are not exceeded:

• the permissible trailer drawbar noseweight
• the permissible trailer load
• the permissible rear axle load of the towing vehicle
• the maximum permissible gross vehicle weight of both the towing vehicle and the trailer

You will find the applicable permissible values, which must not be exceeded, in the vehicle documents.

You will find the values approved by the manufacturer on the vehicle identification plates and those for the towing vehicle in the "Technical data" section.

WARNING

When towing a trailer, your vehicle's handling characteristics will be different in comparison with when driving without a trailer.

The vehicle/trailer combination:

• is heavier
• is restricted in its acceleration and gradient-climbing capability
• has an increased braking distance
• is affected more by strong crosswinds
• demands more sensitive steering
• has a larger turning circle

As a result, the handling characteristics may be impaired and you may lose control of the vehicle. This could lead to an accident with serious or even fatal injuries.

When towing a trailer, always adjust your speed to the current road and weather conditions. Do not exceed the maximum permissible speed for your vehicle/trailer combination.

WARNING

Never depress the brake pedal continuously while the vehicle is in motion, e.g. never cause the brakes to rub by applying constant slight pedal pressure. This causes the brake system to overheat, increases the braking distance and can lead to the brakes failing completely.

WARNING

Under no circumstances try to straighten the vehicle/trailer combination by increasing the speed.

General information

• Do not exceed the legally prescribed maximum speed for vehicle/trailer combinations in the relevant country. This lowers the risk of an accident.
• Only install an approved trailer coupling on your vehicle.
  Further information on availability and on installation is available from any authorized Mercedes-Benz Center.
• The bumpers of your vehicle are not suitable for installing detachable trailer couplings.
• Do not install hired trailer couplings or other detachable trailer couplings on the bumpers of your vehicle.
• To reduce the risk of damage to the ball coupling, remove it from the ball coupling recess when not in use.

When towing a trailer, set the tire pressure on the rear axle of the towing vehicle for a maximum load; see the tire pressure table in the fuel filler flap ().

You will find installation dimensions and loads in the "Technical data" section ().

The maximum noseweight of the trailer drawbar on the ball coupling is20. However, the actual noseweight must not exceed the value given on the trailer tow hitch or trailer identification plates. The lowest weight applies.

Use a drawbar noseweight as close as possible to the maximum permissible noseweight. Do not use a noseweight that is under the minimum permissible noseweight; the trailer may otherwise come loose. Missing values were not available at time of going to print. Note that the payload and the rear axle load are reduced by the actual payload.

Please note that when towing a trailer, PARKTRONIC () is only available with limitations, or not at all.

On vehicles without level control, the height of the ball coupling will alter according to the load placed on the vehicle. If necessary, use a trailer with a heightadjustable drawbar.

Driving tips

Observe the notes on ESP® trailer stabilization ().

The maximum permissible speed for vehicle/ trailer combinations depends on the type of trailer. Before beginning the journey, check the trailer's documents to see what the maximum permitted speed is. Observe the legally prescribed maximum speed in the relevant country.

For certain Mercedes-Benz vehicles, the maximum permissible rear axle load is increased when towing a trailer. Refer to the "Technical data" section to find out whether this applies to your vehicle. If you utilize any of the added maximum rear axle load when towing a trailer, the vehicle/trailer combination may not exceed a maximum speed of 60 mph(100 km/h) for reasons concerning the operating permit. This also applies in countries in which the permissible maximum speed for vehicle/trailer combinations is above 60 mph(100 km/h).

When towing a trailer, your vehicle's handling characteristics will be different in comparison with when driving without a trailer.

On long and steep downhill gradients, you must select shift range 1, 2 or 3 in good time.

This also applies if you have activated cruise control.

This will use the braking effect of the engine, so that less braking will be required to maintain the speed. This relieves the load on the brake system and prevents the brakes from overheating and wearing too quickly. If you need additional braking, depress the brake pedal repeatedly rather than continuously.

Driving tips

• Maintain a greater distance from the vehicle in front than when driving without a trailer.
• Avoid braking abruptly. If possible, brake gently at first to allow the trailer to run on. Then, increase the braking force rapidly.
• The values given for gradient-climbing capabilities from a standstill refer to sea level. When driving in mountainous areas, note that the power output of the engine, and consequently the vehicle's gradientclimbing capability, decrease with increasing altitude.

If the trailer swings from side to side:

• Do not accelerate.
• Do not counter-steer.
• Brake if necessary.

Installing the ball coupling

WARNING

If the vehicle/trailer combination is not secured, the trailer may come loose. As a result, you could cause an accident.

Observe the ball coupling manufacturer's installation instructions and special instructions for use.

Mercedes-Benz recommends that you only use ball couplings that have been tested and approved by Mercedes-Benz. This helps to avoid damage to the vehicle.

Protective cap

• Pull protective cap 1 in the direction of the arrow out of ball coupling recess 2.
• Stow protective cap 1 safely.
• Observe the manufacturer's installation instructions.

WARNING

If the ball coupling is not correctly installed and secured, the ball coupling and the trailer could come loose. As a result, you could cause an accident.

Therefore, please observe the following:

• Ensure that the ball coupling is secured according to the ball coupling manufacturer's installation instructions.
• If the ball coupling cannot be installed as prescribed, detach the ball coupling. Under these circumstances, the ball coupling must not be used for trailer towing.

Have the entire trailer tow hitch checked at a qualified specialist workshop.

Coupling up a trailer

Observe the maximum permissible trailer dimensions (width and length).

Most U.S. states and all Canadian provinces require by law:

• safety chains between the towing vehicle and the trailer. The chains should be crosswound under the trailer drawbar. They must be fastened to the vehicle's trailer coupling, not to the bumper or the axle. Allow for enough play in the chains to facilitate turning tight corners.
• a separate brake system for certain types of trailer.
• a safety switch for braked trailers. Check the specific legal requirements applicable to your state.
  If the trailer detaches from the towing vehicle, the safety switch applies the trailer's brakes.

Do not connect the trailer's brake system (if featured) to the hydraulic brake system of the towing vehicle, as the latter is equipped with an anti-lock brake system. Doing so will result in a loss of function of the brake systems of both the vehicle and the trailer.

The vehicle's wiring harness features a connection to the brake indicator lamp.

• Make sure that the automatic transmission is set to position P.
• Apply the vehicle's parking brake.
• Close all doors and the tailgate.
• Couple up the trailer.
• Establish all electrical connections.

Towing a trailer

There are numerous legal requirements concerning the towing of a trailer, e.g. speed restrictions. Make sure that your vehicle/ trailer combination complies with the local requirements not only in your area of residence but also at any location to which you are traveling. The police and local authorities can provide reliable information.

Please observe the following when towing a trailer:

• To acquaint yourself with driving with a trailer and with the resulting changes to handling, you should practice cornering, stopping and reversing in a traffic-free location.
• Before driving, check:
  - the trailer tow hitch
  - the safety switch for braked trailers
  - the safety chains
  - the electrical connections
  - the lights
  - the wheels
• Adjust the exterior mirrors to provide an unobstructed view of the rear section of the trailer.
• If the trailer features electronically controlled brakes, pull away the vehicle/ trailer combination carefully, manually brake using the brake controller, and check the brakes for correct function.
• Secure any objects on the trailer to prevent the cargo from slipping when the vehicle is in motion.
• If you couple up a trailer, regularly check the cargo for secure fastening and make sure that the trailer lamps and (if applicable) the trailer brakes are functioning correctly.
• Bear in mind that the handling will be less stable when towing a trailer than when driving without one. Avoid sudden steering movements.
• The vehicle/trailer combination is heavier, accelerates more slowly, has a decreased gradient climbing capability and a longer braking distance.
  It is more susceptible to side winds and requires more careful steering.
• If possible, avoid abrupt braking. Depress the brake pedal moderately at first, so that the trailer can activate its own brakes. Then increase the pressure on the brake pedal.
• If the automatic transmission continues to shift back and forth between two gears when driving up or downhill, restrict the shift range. Select shift range 4, 3, 2, or 1. A lower gear and lower speed reduce the risk of engine failure.
• On long and steep gradients that are difficult to drive down in shift range 1, switch to the off-road program or engage the LOW GEAR off-road gear.
• When driving downhill, shift to a lower gear to utilize the engine's braking effect. Avoid continuous brake application as this may overheat the vehicle brakes and, if installed, the trailer brakes.
• If the coolant temperature increases dramatically while the air-conditioning system is switched on, switch off the airconditioning system.
  Coolant heat can additionally be dissipated by opening the windows and by setting the blower fan and the interior temperature to maximum.
• When overtaking, pay particular attention to the extended length of your vehicle/ trailer combination.
  Due to the length of your vehicle/trailer combination, you will have to travel an additional distance beyond the vehicle you are overtaking before returning to the previous lane.

Decoupling a trailer

WARNING

Do not disconnect a trailer with an engaged overrun brake. Otherwise, your hand could become trapped between the bumper and trailer drawbar.

Do not disconnect a trailer with an engaged overrun brake. Otherwise, your vehicle could be damaged by the rebounding of the overrun brake.

• Make sure that the automatic transmission is set to position P.
• Apply the vehicle's parking brake.
• Close all doors and the tailgate.
• Apply the trailer's parking brake.
• Remove the trailer cable and decouple the trailer.

Permissible trailer loads and drawbar noseweights

Weight specifications

The gross trailer weight is calculated by adding the weight of the trailer to the weight of the load and equipment on the trailer. Permissible gross weight: 3500 lbs (1588 kg). The permissible Trailer drawbar Weight Rating is the maximum weight permitted on the trailer drawbar: Limit for Mercedes- Benz-approved trailer couplings.

Loading a trailer

• When loading the trailer, make sure that neither the permissible gross weight of the trailer nor the gross vehicle weight are exceeded. The permissible gross vehicle weight is indicated on the identification plate on the B-pillar on the driver's side of the vehicle.
  You can find the maximum permissible values on the type plates of your vehicle and the trailer. Always observe the lowest respective value when determining the maximum weight with which you can load the vehicle and the trailer.
• The trailer drawbar load on the ball coupling must be added to the rear axle load to avoid exceeding the permissible gross axle weight. The permissible gross vehicle weight is indicated on the identification plate on the B-pillar on the driver's side of the vehicle.

Mercedes-Benz recommends loading the trailer so that the drawbar noseweight remains between 8% and 15% of the permissible gross trailer weight.

The weight of additional accessories, passengers, and cargo reduces the permissible trailer load and drawbar noseweight for your vehicle.

Checking the vehicle and trailer weight

• To check that the weights of the towing vehicle and the trailer comply with the maximum permissible values, have the vehicle/trailer combination (including the driver, passengers, and cargo with a fully laden trailer) weighed on a calibrated weighbridge.
• Check the gross axle weight rating of the front and rear axles, the gross weight of the trailer and trailer drawbar noseweight.

Removing the ball coupling

• Observe the manufacturer's installation instructions.
• Press the protective cap into the ball coupling recess.
• Make sure that the protective cap is firmly in place.

Storing the ball coupling

WARNING

Do not carry the ball coupling in the vehicle interior if it is not secured.

Otherwise, you and others could be injured by the ball coupling being thrown around if you:

• brake sharply
• change direction suddenly
• are involved in an accident

X Observe the manufacturer's installation instructions.

Trailer power supply

The trailer socket of your vehicle is equipped at the factory with a permanent power supply. The permanent power supply is supplied via trailer socket pin 4.

You can connect accessories with a maximum power consumption of 240 W to the permanent power supply. You must not charge a trailer battery using the power supply.

The trailer's permanent power supply is switched off in the event of low vehicle supply voltage and after six hours at the latest. You can obtain further information about installing the trailer's electrical equipment from a qualified specialist workshop, e.g. an authorized Mercedes-Benz Center.