by Richard Luhr
Towing your Mercedes-Benz on a trailer may be the most sensible way to get it where you want it. Here’s how to do it safely.
Trailering is often the preferred way to transport a fine vintage or classic Mercedes, either because the distance to your event is longer than you want to drive the car, or because your new acquisition isn’t yet safe or drivable.
However, it seems that many people don’t attempt to trailer their own cars because trailer towing seems mysterious or difficult. In fact, it’s not hard at all. It’s simply a matter of understanding the basic principles and taking some care to prevent mistakes.
Typically trailer towing is done with full-size pickups that are equipped for towing with options like a receiver hitch, auxiliary transmission cooler, and an electric brake controller. If you want to tow a Mercedes with a Mercedes, the late-model GL and ML classes are excellent choices. In any case, the first step is always to compare the weight of the load you plan to tow to the “towing capacity” rating of the tow vehicle and the rating printed on the tow vehicle’s hitch.
If you don’t know the weight of your vehicle, it’s easy to get an accurate weight at a truck stop with a CAT Scale (www.catscale.com). The cost is only $9. Add that to the weight of the trailer you plan to use. Open, lightweight aluminum trailers can weigh less than 1,000 pounds, while a fully-enclosed steel framed trailer can easily weigh over 3,000 pounds.
If you are trying to choose which type of trailer to use, consider that an open trailer is lighter, less expensive, and allows you to see the car while towing. On the other hand, a fully-enclosed trailer protects the car and hides it from view, which is good for high-value cars. Verify that whatever trailer you use is rated to carry the weight of the heaviest vehicle you plan to transport.
A 3,000 pound car on an open trailer is easily managed by many tow vehicles, but regardless of weight, trailer loading is a critical step. Trailers need to have slightly more of their weight toward the front in order to handle properly on the road. The amount of weight on the hitch ball is called “tongue weight,” and most sources recommend 10-12 percent of the total trailer weight on the tongue. If the tongue weight is too low, the trailer will be prone to swaying – a dangerous condition. Fortunately, car trailers are usually designed so that when the car is in place most of its weight is forward of the trailer axles, which helps ensure that the tongue weight is close to spec.
The trailer also needs brakes. In most states it is illegal to tow a trailer over 1,500 pounds without brakes, and even if not legally required, brakes are always a good idea. Lightweight trailers may incorporate “surge” brakes, which use a plunger (master cylinder) on the front of the trailer to activate the trailer brakes. The advantage of this system is that it requires no special modification of the tow vehicle, making it ideal for rental trailers.
Heavier trailers do better with electric brakes, controlled by a brake controller in the tow vehicle. The brake controller sends a variable voltage signal to the electric brakes on the trailer, in proportion to the braking force of the tow vehicle. More voltage means stronger braking. An electric brake controller is not a factory option on most vehicles (including Mercedes) but if your tow vehicle needs one, it can be easily added by any RV or trailer shop. Follow the brake controller manufacturer’s instructions to get the controller dialed in to the optimum setting for your trailer.
A trailer with electric brakes will also have a small battery and a “breakaway cable” installed. The breakaway cable is attached to the tow vehicle. If the trailer comes loose during towing, the cable will yank a pin on the trailer’s breakaway switch, and this will activate the trailer brakes, using the on-board battery as a power source.
But you don’t ever want that to happen, so the next step in preparing to tow is to secure the trailer to your tow vehicle. The hitch ball is easy to connect, but verify you’ve got the correct size of ball for the trailer. Hitch balls come in several sizes, the most common being 2-inch and 2-5/16 inches. The size is printed right on the ball. Check that the ball is tight, and maybe throw a little grease on it just to keep it from squeaking as you go down the road. After connecting, give the trailer tongue a good yank upward to be sure that the hitch ball clasp is fully engaged.
Always use the supplied safety chains. These should cross beneath the hitch ball. The idea is that if the ball comes loose, the trailer will fall onto the crossed chains and avoid dragging on the ground as severely.
The final connection is the electrical connector. This connector is usually either a flat 4-pin (for trailer lights only) or a round 7-pin connector (with signal pins for lights and the electric brakes). If your tow vehicle has a 7-pin round connector and the trailer needs only 4-pin, adapters are easily found at hardware stores. Once connected, go around and verify that all the lights and brake/turn signals are functioning properly.
If you’ve never towed before, it might be a good idea to tow the trailer around a little without a car in/on it. Get a feel for the length of the trailer and how it goes around corners. Electric brakes might be a little touchy with no load on the trailer, so keep in mind that you’ll check the trailer brakes again after you’ve got the car on board. When you get back to your starting point, double-check that the trailer has no broken parts or loose wires, and that the trailer wheel hubs didn’t get unduly hot (a sign of a dragging brake or bad bearings).
Be sure to practice backing it up. Find a big empty parking lot and put up a few pylons or boxes to form a slot a little bigger than the trailer and try backing the car into the slot. It will take awhile to get used to the fact that the back end of the trailer will move opposite to the direction that the back of the tow vehicle is moving. A simple rule is that the bottom of the tow vehicle steering wheel needs to go in the direction that you want the back of the trailer to go.
All of this prep is designed to ensure you’ve got a solid foundation for your prized Mercedes.
Before you even load the trailer, check the trailer’s tires. Are they worn, cracked, or damaged? Verify proper air pressure, and check the lug nuts for tightness as well. Keep in mind that your tow vehicle manufacturer may recommend adding air to the tires when towing, so check the Owner’s Manual. Finally, make sure you have a good spare tire for the trailer and the tools to replace it.
Now it’s time to load up. Start in a place where the ground is level and firm. Put the tow vehicle in Park, set the parking brake, and consider using some wheel chocks on the trailer, too. The idea is to keep the entire rig stable as you put your pride-and-joy on it.
We’ll assume your car is drivable, otherwise you’ll need a winch or several helpers to push the car. (If you are buying your own trailer, a winch should be a necessity since it allows you to move the car unto the trailer without driving it.) In any case, have someone standing by to help guide you up the ramps and into/onto the trailer.
Once the car is in position, you can start tying it down. This is the part that tends to freak people out – what if I don’t get it tight and it goes airborne on the Interstate? Don’t worry too much. Use a set of nylon ratchet straps and nylon axle straps to connect the chassis and axle to the D-rings on the trailer. Never tie down the body of the car, or any part of the “sprung” vehicle weight, because bouncing of the car will over-stress the trailer’s D-rings and can cause them to fail. The best set-up is to use strap harnesses that are designed to wrap over the wheels.
Otherwise, wrap the axle strap around the axle housing in the rear, and then use the ratchet straps to increase tension. If fastened to the suspension, fasten the rear straps to the opposite corner of the trailer. Up front, wrap the axle strap around something that won’t cut the strap – like an A-arm, chassis rail or solid front axle—and use the ratchet straps to finish tying the car down. Be careful not to secure the straps around the sway bars, steering arms or the steering rack. When positioning the straps, make sure that no brake or oil lines are crushed.
When you are satisfied, it’s time for one more safety check, and then you can go for a short spin. Take a look at everything you’ve done (hitch coupler, safety chains, electrical connector, tie-downs) and make sure it all looks good. Turn on the tow vehicle lights and check to make sure that the trailer running lights, brake lights, turn signals, and flashers are all operational.
As you pull out for the first time with your car on the trailer, listen for strange noises and travel slowly at first. You might need to adjust the brake controller slightly as the brakes warm up (or break in, if they’re new). Before you’ve gone 25 miles, stop to check the tightness of your straps. New or wet straps are prone to stretching. After that initial stop, it’s a good idea to check the straps and chains every time you break for fuel or food and following any severe stops. A brief walk around the trailer at every stop will help you spot issues with tires or trailer equipment as well.
Although your car might get dirty when towing with an open trailer, don’t cover it while in motion. The flapping of a cover on the highway can cause damage to the paint. Wash the car when you arrive, and bring a cover to put on the car while it is parked overnight.
Once you’ve trailered your Mercedes a few times, you’ll find it’s actually quite easy. It’s even easier if you make a short checklist of tasks, safety items, and tools needed for each tow. With that in hand, your chance of an expensive mistake will be greatly reduced, and you’ll be able to enjoy taking your fine car longer distances with no stress.
Photos courtesy of Bruce S. Dickey, Classic Car Collector, 408 N. Church St, Suite D, Greenville SC 29601, [email protected]. (864) 915-7823 Car: 1962 220SE Cabriolet, 69,000 miles.
Captions: Do not exceed the rated maximum load weight and maximum tongue weight for your tow vehicle (in the owner’s manual) and on the trailer. For moderate loads up to 3,500 pounds a surge brake system will work. For heavier loads, an electronic brake should be installed on the tow vehicle.