Towing The Line

Towing the Line

Story & Photos by Bruce W. Smith
Inside Tow Ratings and What they Mean to You




Imagine heading out with your friends to an off-road play area towing a 24-foot toy hauler, loaded with quads and gear, behind a brand new diesel-powered "one-ton" pickup. Such a task would be an effortless one; after all, towing 7,000 pounds behind a pickup with a maximum towing capacity of more than six tons could hardly be called a big load.

Now imagine being in an accident with that trailer in-tow. There are injuries in the other vehicle, in yours, or both. To your surprise a lawsuit ensues. That is followed by you being found liable for a multi-million-dollar judgment to the people injured in the accident because of towing beyond your pickup's maximum capacity.

Never happen? Don't bet on it. The above scenario is an all too real a possibility.
Even though you thought your new ride could tow 12,000 pounds, one small detail, noted in the owner's manual, was missed: the difference between "weight-carrying" and "weight-distributing" maximum towing capacities.

If you had the trailer hooked to a standard hitch instead of a weight-distributing hitch, as is often the case, the truck's maximum weight-carrying capacity was probably a lot closer to 6,000 pounds than 12,000-plus. Oops.
Weight Carrying vs Weight Distributing

The towing section of owners' manuals discuss these two towing terms as do the manufacturers' web sites related to trailering. But many vehicle owners don't understand weight-carrying and weight-distributing have completely different meanings and are not interchangeable. Understanding the differences is critical if you intend to tow in a safe, prudent manner. 


The weight-carrying trailer-towing capacity is the maximum weight the particular vehicle can tow safely in the conventional mode, which is attaching the trailer directly to the ball on the shank coming out of the hitch.

The weight-distributing trailer-towing capacity, which is the rating always referred to in advertisements and by salespeople, is when the trailer is attached to a weight-distributing (load-equalizing) hitch assembly.

A weight-distributing hitch utilizes supplemental steel bars, called spring-bars, attached between the trailer and the hitch receiver. These spring-bars are adjusted with chains or some other method to distribute the weight of a heavy trailer more evenly across the tow vehicle's front and rear axles, enhancing the tow vehicle and trailer's stability and handling characteristics.

Consequently, a vehicle's weight-distributing towing capacity will always be significantly higher than the weight-carrying towing capacity. And if you tow beyond either's limits you are treading on very thin legal ice. 

Law Of Negligence
Trailered loads exceeding the weight-carrying capacity as specified in the vehicle's owners' manuals, must be equipped with a weight-distributing hitch in order to meet the vehicle manufacturer's higher tow rating - and allow you to be towing in a safe and prudent manner. That's really important.

Towing beyond any vehicle's manufacturer's weight ratings-or without regard to the properly-equipped limitations a vehicle's manufacturer places on the towing vehicle-relates directly to the "Law of Negligence", and places you, the driver, bearing the full weight of liability issues.

"A plaintiff who was injured as a result of some negligent conduct on the part of a defendant is entitled to recover compensation for such injury from that defendant," quotes Richard Alexander, a major injury trial attorney in San Jose, California. 
"One test that is helpful in determining whether or not a person was negligent is to ask and answer the question whether or not, if a person of ordinary prudence had been in the same situation and possessed of the same knowledge, he or she would have foreseen or anticipated that someone might have been injured by or as a result of his or her action or inaction.


"If the answer to that question is 'yes,' and if the action or inaction reasonably could have been avoided, then not to avoid it would be negligence," warns Alexander. (For more about this subject go to www.alexanderinjury.com.)

Two Powerful Towing Words
The negligence issue gets back to the tow vehicle being "properly-equipped." Those are some words with real weight. You see them in every owners' manual and TV ad related to tow towing. Those two words are the automotive version of an electrified fence between towing with the full blessing of the vehicle manufacturer and not. 
A properly-equipped vehicle has everything the manufacturer deems necessary to tow a certain load-the proper engine and transmission; the correct bed and cab configuration; and with the right axle ratio and hitch setup.

For example, Ford F-150, F250/350s single-wheel models (www.fleet.ford.com/showroom/rv_trailer_towing/2007/2007_default.asp) are limited to 5,000 pounds in the weight-carrying mode, as are 1500 Series GM pickups (www.chevrolet.com/silverado/specifications), Dodge Ram 1500s (www.5.dodge.com/vehsuite/TowingGuide.jsp), and 2008 Toyota Tundras. 
Thumb back to the towing section of any pre-2007 Toyota pickup and SUV owners' manuals and you'll see sway-control devices are mandatory on trailers weighing more than 2,000 pounds. Toyota also limits towing speeds of those vehicles to less than 45mph.

Read Nissan's towing guide and it "strongly recommends" the use of a sway-control device for all of their pickups and SUVs when towing trailers weighing more than 2,000 pounds. Do you have a sway-control device on that four-place ATV trailer your Titan is towing?

But be forewarned, sway-control devices are considered by the majority of trailer manufacturers to be an absolute "no-no" on surge-brake-equipped trailers, because while controlling sway, they also prevent the very compression movement between the hitch and the trailer that activates the surge-brake system.

Tongue Weight Heavy Issue
Owner's manuals and the hitches list a second weight limit: maximum tongue weight.  Tongue weight is the downward force a trailer tongue places on a hitch ball, and therefore on the rear of the tow vehicle.  Tongue weight is expressed either in pounds or as a percentage of the total towed weight.

Like weight-carrying and weight-distributing, tongue-weight has been derived by both the vehicle and the hitch manufacturer as the safe limit for that product. Tow a trailer that is outside of the tongue-weight specified by the vehicle manufacturer and you are being negligent.

As the online Dodge towing guide states, "Incorrect tongue weight could result in increased yaw or vehicle instability. A negative tongue weight could unload the rear suspension of the tow vehicle, decreasing vehicle stability."
If either tongue-weight or the hitch load limitations are not adhered to, you are considered to be towing in a negligent manner. 

Surge-Brake Trailers Special Issue
The conundrum here is even if you abide by tongue-weights and use a weight-distributing hitch so the tow vehicle is properly-equipped, it still may not be right.  Off-road adventurers need to pay heed to the affect weight-distributing hitches and "sway-control" devices have on trailers equipped with surge-type brakes.
Surge-type brakes are those that have a hydraulic master cylinder in the trailer tongue, which uses the force of the trailer pushing against the tow vehicle to apply the trailer's brakes. This type of brake system is very common on boat, entry-level toy haulers, and utility-type trailers.

What is at issue here is the majority of weight-distributing hitches interfere with (or disable) the surge-type brake system and keep it from functioning properly. Sway-control devices, like those required by many of the smaller SUV and pickups to tow larger loads, virtually stop a surge-brake system from working at all.
 The good news is both Equal-i-zer (www.equalizerhitch.com) and Reese SC (www.reese-hitches.com) offer special weight-distributing hitches designed for use with surge-brake-equipped trailers.

If you trailer a surge-brake-equipped trailer that weighs enough to require the use of a W-D hitch, it'd pay to utilize one of these models.
Manufacturer-Induced Confusion
Don't blame yourself for not knowing these little caveats about towing. Automotive manufacturers are always pushing for a marketing edge, and tow ratings play a big role in that edge. Regardless of how small the difference is between two competing vehicles, the one with the bigger towing capacity is somehow perceived as being the better vehicle.

So almost every ad you see on TV shows a truck or SUV towing at or very near its upper limits. This leads the average buyer to believe their vehicle can do the same without the use of any additional towing equipment or accessories.

What makes things even worse is none of the current tow ratings are from standardized tests; every vehicle manufacturer has their own testing criteria. That opens the door to change a vehicle's tow rating with the stroke of a pen should a competitor come out with a bigger number. This situation is about to change.

Three years ago a group of towing engineers within GM helped set up a tow vehicle trailer rating subcommittee within the Society of Automotive Engineers (SAE) in an effort to bring clarity and common sense to tow ratings. The guidelines are being formed in SAE J-2807, "Performance Requirements for Determining Tow Vehicle Gross Combination Weight Ratings and Trailer Weight Ratings."
"Ultimately, the goal we are striving for is that when you see a 5,000-, 7,000-, or 15,000-pound trailer rating, it will mean the same whether it comes from Ford, GM, Chrysler, Toyota, Nissan, Honda, or any other vehicle manufacturer," says Robert Krouse, one of the key GM engineers involved in the SAE standardization effort.
"We have reps from all of those companies in this subcommittee, along with representatives from RVIA (the Recreational Vehicle Industry of America), NATM (the National Association of Trailer Manufacturers), and indirectly from NMMA (the National Marine Manufacturers Association). As an industry, we're aware of these [confusing] towing and tow-rating issues.

The latest information from SAE is some of the new towing standards found in SAE J-2807 may come into play on TV advertisements as soon as mid-2008.
No Escaping Tow Ratings
Trailer weight capacity issues create some interesting towing calculations and confusing legal issues for anyone who attaches a trailer to a hitch. And, no, you can't work around a vehicle's towing capacity limitations by upgrading to a stronger hitch, say from a Class III to a Class IV or V, or by adding helper springs.
We have to live with and abide by the tow ratings the vehicle manufacturers set. If you ignore the ratings and words such as "properly-equipped" and "weight-carrying limit," then you assume all responsibility for what happens down the towing road.  

Editor's note: Bruce W. Smith is a contributing editor with ORA and the author of "The Complete Guide To Trailering Your Boat," just published by McGraw-Hill/International Marine Press (www.mhprofessional.com/product.php?isbn=0071471642)

HITCH RATINGS
Look closely at the hitch on your truck and you'll see the weight-carrying capacity clearly indicated. This number is the maximum weight the hitch manufacturer deems safe for towing with that particular hitch configuration. The limit indicated on the hitch may be higher or lower than the weight-carrying limit on the vehicle-especially if you're purchasing a used vehicle whose previous owner installed the hitch.
If the two ratings don't agree, the lower figure of the two always takes precedence because that's the limit of the weakest link in the towing connection.

TOW RATING EXAMPLES

Vehicle   Weight-Distributing Capacity  Weight-Carrying Capacity
          (Class III hitch)

'06 Dodge Dakota QC 4WD   6,926 lbs *  3,000 lbs (300 lbs TW)

'06 Dodge Ram 2500 QC SB 2WD  9,100 lbs *  5,000 lbs (500 lbs TW)

'06 Jeep Commander     7,050 lbs *  5,000 lbs (500 lbs TW)

'07 Chevy Tahoe 4WD    7,700 lbs. *  5,000 lbs (500 lbs TW)

'08 GMC Sierra 1500 CC 4x4   8,500 lbs.*  5,000 lbs (500 lbs TW)

'08 Toyota Sequoia     10,000 lbs*  5,000 lbs (500 lbs TW)

'08 GMC Sierra 2500HD CC 4X4   13,000 lbs*  7,500 lbs (1,000 lbs TW)

'06 Toyota Tundra Double Cab 4WD  7,000 lbs. *                        2,000 lbs (200 lbs TW**)
    
'08 Toyota Tundra Double Cab 4WD  10,300 lbs*  5,000 lbs (500 lbs TW)                                                 

'07 Ford F-150 Super Crew 2WD   9,200 lbs*  5,000 lbs (500 lbs TW)

'08 Ford F250/350 Super Duty SRW  12.500 lbs*  5000 lbs (500 lbs TW)

'08 Ford F350 Super Duty DRW   16,000 lbs*  6000 lbs. (600 lbs. TW)

'06 Ford Explorer     7,300 lbs *  5,000 lbs (500 lbs TW)

(TW= Tongue Weight)
* * Requires use of Class IV Weight-Distributing Hitch
* ** Requires use of sway-control device above 2000 lbs, which disables trailer surge brakes

Notes: ALWAYS READ YOUR VEHICLE OWNER'S MANUAL AND LOOK AT THE HITCH RATING LABEL BEFORE TOWING TO MAKE SURE THE VEHICLE AND TRAILER ARE COMPATIBLE. 
 
VEHICLE WEIGHT RATINGS  [Use image 0702GM HD Towing Toy Hauler.tif]
There are limits to how much load your vehicle can carry safely. These limits include how much it can carry on each axle, the total combined weight it can carry, and how much it can tow.  Each of these limits is important to vehicle durability and handling. Surpass any one of them and you put yourself, your passengers, and your vehicle, and other sharing the roadways with you at risk.

Automotive manufacturers provide this information in the form of Gross Weight Ratings listed in the owner's manual, inside the glovebox, or on the edge of the driver's doorpost.  Here's what the ratings mean:

* GROSS AXLE WEIGHT RATING (GAWR) is the load-carrying capacity of a single axle. Note that there are separate GAWRs for the front (FGAWR) and rear (RGAWR) axles-and these ratings are limited by the lowest-rated component's load carrying ability, whether tires, wheels, springs, or the axle housing itself.

* GROSS VEHICLE WEIGHT RATING (GVWR) is the maximum allowable loaded weight of a vehicle. This weight is the combination of the vehicle's curb weight (with full fuel tank) added to the vehicle's maximum payload capacity, plus the weight of the driver and passengers.

* GROSS COMBINED WEIGHT RATING (GCWR) is the maximum allowable loaded weight of a vehicle and the trailer it tows. It is the sum of the vehicle curb weight plus the weight of driver, passengers, bed payload, trailer tongue weight and towed trailer weight. -BWS


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