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Old 04-24-2015, 10:47 AM   #1 (permalink)
Tom S.
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Towing's Alphabet Soup

People who tow are familiar with this, but those new to the towing world can run afoul of the towing alphabet soup. For that reason, here are the various letter combinations and what they stand for, as well as a description of their use.


GVW = Gross Vehicle Weight

Definition: is the actual combined mass of a vehicle including passengers and cargo. In other words, how much your truck (a.k.a. tow vehicle) weighs after loading it up for towing. Note that it includes passengers and cargo. Cargo includes your dog(s) and any camping gear you plan to carry in the truck. That means you can't just go get your truck weighed when you get it to determine this weight, or rely on the manufacturer's stated vehicle weight.


GVWR = Gross Vehicle Weight Rating

Definition: is the maximum operating weight/mass of a vehicle as specified by the manufacturer including the vehicle's chassis, body, engine, engine fluids, fuel, accessories, driver, passengers and cargo but excluding that of any trailers. This looks very similar to GVW but it is not the same! GVW is the actual weight of the vehicle while GVWR is the manufacturer's statement of what the limits of that actual weight is. For example, if your truck has a GVWR of 9,200 pounds and the GVW (actual weight) of the truck when loaded is 9,100, it is 100 pounds under the GVWR. On the other hand, if the truck has a GVWR of 9,200 and the GVW is 9,350 the truck is over the CVWR by 150 pounds. Time to give Aunt Emma the boot!


GCVR = Gross Combined Weight Rating

Definition: is the maximum allowable combined mass of a towing road vehicle, passengers and cargo in the tow vehicle, plus the mass of the trailer and cargo in the trailer. This rating is set by the vehicle manufacturer. In a practical example, if your truck GCVR is 22,000 pounds and the truck's GVRW is 9,200 pounds then in theory, your truck can pull a trailer that weighs no more 12,800 pounds. Why the "in theory" statement? Here's why: if your truck's GVWR is 9,200 pounds and it weighs less than that, you can add the difference to the 12,800 pound figure. On the other hand, if the truck weighs more than the GVWR (a bad thing!), that difference must be subtracted from the 12,800 pound figure.


GAWR = Gross Axle Weight Rating

Definition: is the maximum distributed weight that may be supported by an axle of a road vehicle. Typically, GAWR is followed by either the letters FR or RR, which indicate front or rear axles respectively. These are important numbers many campers or people who tow other types of trailers forget to take into account. If a truck's GVWR is 9,200 and it weighs 9,000 then all's good - right? Not necessarily so! Each truck also has weight limits on it's front and rear axles. For example, the front axle may have a limit of 3,200 pounds while the rear axle has a limit of 6,000 pounds. You drive to the local scale to weigh your loaded truck and it weighs 9,000 pounds, but you then weigh just the front axle and find out it shows a weight of 2,800 pounds. Subtracting that 2,800 pounds from the overall weight of 9,000 pounds leaves 6,200 pounds on the rear axle (you can weigh the rear axle to confirm this, but numbers, at least in this case, do not lie!). So the rear axle is 200 pounds over the manufacturer's weight rating.


GTWR = Gross Trailer Weight Rating

Definition: the gross trailer weight rating (GTWR) is the total mass of a road trailer that is loaded to capacity, including the weight of the trailer itself, plus fluids, and cargo, that a vehicle is rated to tow by the manufacturer. In the United States and Canada, the static tongue load, the weight of the trailer as measured at the trailer coupling, is generally recommended to be 10-15% of the GTWR. Just like your truck, the trailer also has a GAWR, however to find it out, you may have to crawl under the trailer to find out what the rating is. It should be stamped or tagged on each axle. And just as was pointed out under the discussion on GAWR for trucks, you cannot assume that because a trailer is under the GTWR that one of the axles isn't overloaded.


The last, but equally important are of discussion in this topic of weights are tires and rims. It is important to make sure the specifications for both the tires and rims exceed the weight specifications of each axle. This is especially important when talking about tires designed for trailer use only. These tires, labeled Special Trailer (or ST for short) have higher carrying capacities than similar sized and rated Light Truck (LT for short) tires. For example, a 235/80/16 Load Range "E" 10 ply ST tire is rated for 3,520 pounds at 80 psi while a 235/85/16 Load Range "E" 10 ply LT (light truck) tire will have rating of only 3,042 pounds at 80 psi. The differences don't stop there either. ST tires are rated for a maximum speed of 65 mph, while truck tires can, in some brands, exceed 100 mph. LT tires are also mandated by the Federal Government to have a reserve load capability, while ST tires have no such requirement. These last two differences are why many trailer owners opt to use LT tires in place of ST tires when the rating of the LT tire is sufficient for the trailer's weight rating.



For those who may be wondering about the difference in trailer hitch classes, the chart below should be of assistance.

  • Class I — rated to 2,000 pounds (907 kg)
  • Class II — rated to 3,500 pounds (1,588 kg)
  • Class III — rated to 5,000 pounds (2,268 kg)
  • Class IV — rated to 10,000 pounds (4,536 kg)


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Last edited by Tom S.; 05-01-2015 at 02:46 PM.
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Old 04-29-2015, 09:12 PM   #2 (permalink)
Franka548
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Nice write up Tom, this should help those that are new to the towing world.
Frank

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Old 05-01-2015, 01:07 PM   #3 (permalink)
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Nice write up!
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Old 05-01-2015, 02:40 PM   #4 (permalink)
Tom S.
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Thanks guys!
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Old 07-14-2015, 12:56 AM   #5 (permalink)
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GAWR

Is the gross axle weight rating (rear) of 6200 lbs per each wheel or both wheels combined?
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Old 07-14-2015, 02:52 AM   #6 (permalink)
Franka548
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It is for the axle,(both wheels)
Frank
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