Towing Requirement- I'm probably getting way too technical, but ...

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GaryB

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Jul 29, 2006
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Evansville, IN
Just was wondering about the formula that uses 10%-20% added to GVWR to determine the towing requirement (i.e., max tow capacity) for a tow vehicle....

Why is the towing requirement for a tow vehicle dependent of GVWR rather than actual loaded weight?  Please let me explain.  GVWR (or GVWR minus dry weight) is a "capacity" figure, whereas loaded weight is an "actual figure".  For example, suppose Trailer X has dry weight of 6000 lbs and GVWR of 8000 lbs.  Suppose Trailer Y has dry weight of 6500 lbs but GVWR of 7800 lbs.  The formula I mentioned above (using GVWR) would say that Trailer X would need a beefier tow vehicle (since it has a higher GVWR) -- even though it is 500 lbs lighter (=6500-6000) than Trailer Y.  So although Trailer X may be 'sturdier' since it can handle 2000 lbs of cargo/tanks (=8000-6000) instead of 1300 lbs for Trailer Y (=7800-6500), that doesn't mean that Trailer X is heavier than Trailer Y given a fixed cargo/tank load.  Of course, tow vehicles don't care how "sturdy" a trailer is (based on GVWR), only how much the loaded trailer weighs (based on dry weight + cargo). 

In summary, what I'm asking is - for a fixed cargo load, wouldn't the trailer with a higher dry weight need a beefier tow vehicle, as opposed to the trailer with the higher GVWR?  If so, would it be a better indicator to inflate "dry weight" by a certain percentage rather than "GVWR"?  The reason I ask is because I've noticed that some trailers have a higher dry weight but a lower GVWR than another trailer.

I'm probably making this way too complicated.  It's getting late now and I'm starting to confuse myself!
Gary
 

Karl

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Gary,

Your logic is sound, but doesn't take into account Murphy's Law, which states (and I paraphrase) "The contents of any container will expand to fill the capacity of the container." If you always carried a fixed amount of gear, say 1000 lbs, over and above the dry weight, then the lighter dry weight trailer would require a lesser tow vehicle. Real life, however, says that you'll pack everything INCLUDING the kitchen sink and you'll travel hilly roads you never intended to travel, so it's smarter to base your calculations and tow vehicle selection on the GVWR rather than dry weight plus what you 'think' you're going to carry. 
 

DougJ

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Mar 7, 2005
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Real life, however, says that you'll pack everything INCLUDING the kitchen sink and you'll travel hilly roads you never intended to travel, so it's smarter to base your calculations and tow vehicle selection on the GVWR rather than dry weight plus what you 'think' you're going to carry. 

And then, Gary, you'll likely delude yourself as to how much that stuff you packed in actually weighs.  So, whether you'retrying to adhere to the GVWR or something less, you never know for sure until you weight your rig. 

Ciao,

Doug
 

Carl L

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Mar 14, 2005
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west Los Angeles
Why is the towing requirement for a tow vehicle dependent of GVWR rather than actual loaded weight?

An actual weight of a trailer as loaded for travel does indeed supercede a GVWR.? ?If you have that, use it.

HOWEVER, how many times does a trailer buyer have that?? Only when he already owns the trailer and is buying a truck to haul it with.? ?Most folks here own the truck and are buying the trailer or are buying both.? ?A trailer dry weight is a weight estimated by the mfr and may omit important options like awnings or batteries and essentials like food, baggage, water, propane, etc..? ?

So what is a buyer to rely on?? His own wishful estimates of how lightly he can travel?? ?That is usually an exercise in kidding himself.? ?The GVWR is a real number.? It is the number that the mfr furnishes the DOT about his rig.? It the limit that the trailer can carry plus its own weight.? ?

So what do we use, a number that permits wishful thinking and shaving safety factors, or a number that is concrete, found on every DOT plate on every trailer, used or new.? ?If I am going to recommend cautiously, I am going to go with pessimistic numbers to come to a safe conclusion.? ?If a person wants to use their own numbers and ignore our advice ... well shoot it is a free country and we are all over 21.? ?Lord knows we are over 21. ;D
 

GaryB

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Jul 29, 2006
Posts
223
Location
Evansville, IN
Thanks all for clearing that up.  I thought it was just due to taking a conservative approach as you all verified.  I agree, in absence of knowing the true loaded weight and/or being strict and consistent about how much cargo one packs, the GVWR is the safest approach.

Gary
 
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