Trailer Towing



Trailer towing capacity has been written about several times so far, but the act of actual towing is something that many people do, and few know anything about before doing it the first time.  Add to this the fact that there are no trailer towing schools outside of semi truck driving school.  This is why there are so many TV advertizements depicting theoretically humorous trailer towing mishaps and blunders.  A slight mistake or omission can lead to a spectacular accident.


A trailer, by its very definition is attached to the tow vehicle, and like a horse, is led around by the nose.  However, like a horse, it sometimes develops tendencies of its own, and handling it under these circumstances can be quite exciting, as in dangerous.


First, know the actual weight of your trailer.  The weight of the payload must be added to the weight of the trailer to know how much weight the tow vehicle is pulling around.  If you tow a boat, add the weights of the fuel (7 lb per gallon), batteries, skiing or fishing equipment, anchor, ropes, etc, etc, to get the total trailer weight.


Next, consider what you are towing a trailer with.  There are four capacities that must be considered when looking at trailer towing:


  1. Trailer towing capacity of the tow vehicle.  This is a manufacturer’s rating.  It takes into account the strength of the frame, engine, brakes, transmission, cooling system, etc.  Many times, the manufacturer’s rating is predicated on the installation of specific factory options or equipment, like suspension, engine/transmission cooling, or final drive ratio options.  It, also, depends on how much weight is being carried on or inside of the tow vehicle.  The Gross Vehicle Weight Rating or GVWR is the manufacturer's rating for the maximum total weight of the loaded trailer plus the loaded tow vehicle’s weight, including people, luggage, equipment, etc.  Neither the trailer towing capacity nor the GVWR can be exceeded.


  1. Tow hitch capacity.  This is the tow hitch manufacturer’s trailer weight rating, and it has two components:  the weight on the trailer ball when the vehicle is sitting still (tongue weight) and the total weight of the trailer (trailer weight).  Even if the tow vehicle is rated to tow 5000 lb, if the hitch rating is 2000 lb, you can only tow 2000 lb.


  1. Tire weight ratings.  This includes the tires on the tow vehicle and the trailer.  Each tire has a weight rating on the sidewall that should not be exceeded.  A trailer with a 400 lb tongue weight puts 400 lb extra on the rear tires of the tow vehicle (in most cases).  Exceptions to this are load distributing hitches.  In these cases, consult the hitch manufacturer on how much of the load is carried by the front and rear wheels of the tow vehicle.


  1. Trailer weight capacity.  This capacity is usually either stamped on a plaque on the trailer or written in the trailer manufacturer’s literature.  That capacity is dependent not only on the trailer frame, but also on the capacity of the trailer tires.


When you tow a trailer. The lowest of the above four ratings is the maximum weight of the trailer that you can tow.


















When loading the trailer, ensure that at least 10% of the trailer’s weight is on the tongue (the trailer ball).  This is especially critical on short and/or single axle trailers.  With a rearward weight bias, trailers will tend to sway from side to side as the tow vehicle goes straight down the road.  Each time it sways, it is trying to pull the tow vehicle off course.  Not good.  Trailers with two or more axles or very long trailers have less tendency to sway, but a forward weight bias (as stated by the trailer manufacturer) is still recommended.


When loading a trailer, ensure that the load on the trailer does not move around.  That could cause the trailer to make really wicked moves when you have to make an emergency maneuver.  Trailer cargos must be tied down or secured tightly.  Your boat may weigh 4000 lb, but if the trailer takes a serious bump in the road, the boat can take on the characteristics of an aircraft.


Acceleration, braking, and turning will be significantly (negatively) affected by the trailer.  Stopping distances can easily double, and repeated brake use can fade brake effectiveness quickly where the same brakes would not normally fade at all.  Many trailers have their own braking systems, but your vehicle and trailer will still take longer to stop than your vehicle alone will take to stop.


While towing, keep in mind that the trailer will turn inside the track of the tow vehicle.  That is why a tractor trailer rig turns so wide at intersections.  This effect is made larger or smaller by the length of the trailer.  The further the wheels of the trailer are behind the wheels of the tow vehicle, the further inside the turn they will track.  Also, the sharper the turn, the further inside the turn they will track.


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When backing a trailer, the shorter the trailer, the faster it will veer off your intended course.  A 4X7 or 5X8 UHaul trailer will be very difficult to back with a long tow vehicle (like a 4 door crew cab pickup or a Suburban).  The long tow vehicles simply cannot correct the tendency of the short trailer to turn quickly enough.  The opposite of this is the tractor/trailer trucks of the open highway.  Backing the long trailers with the short tractors is a snap.  (Getting them to stop from highway speeds in a straight line?  That’s another story, and it can end in what is called “jack knifing”.)


Lastly, when backing a trailer, there will be times when there will be blind spots in the trailer’s path.  Ensure that either you have people watching your blind spots and talking to you, or you stop and get out frequently to check your path.


It is important to consider tow vehicles for the type of trailer towing, not just for the trailer weight.  When towing a boat, you must, also, consider whether the tow vehicle will be able to get the boat up a wet (slippery) launch ramp with a 20 degree slope.  That’s not just a matter of power.  A two wheel drive pickup with nothing in the bed or a front wheel drive vehicle will be at a disadvantage in this endeavor, especially if the trailer weighs more than approximately 2000 lb.
















When towing at highway speeds, the air drag caused by the (normally unaerodynamic) trailer can double every few miles per hour of speed increase.  This puts a tremendous strain on the transmission and engine.  Consider supplemental cooling equipment and more frequent fluid changes for the tow vehicle.  You might even slow down a notch or two.


Lastly, many trailers are taller than the towing vehicles.  Just because your car can make it into carport or under a bridge, that does not ensure that the trailer can get under the same obstacle.


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