Weighing and fifth wheel trailers (Nerd stuff)

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MtnGoat

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After reading the library article "Weighing trailers -- travel and fifth wheel trailers", hit a local public scale to get some numbers. I like to know these things as part of the ownership. So If my total GVRW is 17,920#. And the total rig weight 16,040#, then I'm 89% of legal wet maximum rig weight.  Yes?

But if I add the GVWR axle ratings, this number is 17,800#. SO the difference is 120#.

No big deal?
 

longhaul

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And the total rig weight 16,040#, then I'm 89% of legal wet maximum rig weight.  Yes?
JFY.....GVWR isn't used as any legal definition  to determine a vehicle "legal wet weight" as you call it.....however your weights look good
  I keep a scale ticket of the front and rear axle weights for the car...all my trucks and all the trailers empty axle weights.
 

Gary RV_Wizard

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On a trailer, the axle weight ratings (GAWRs) are less than the total GVWR because part of the trailer weight is carried on the hitch (aka tongue or pin weight).  Typically for a travel trailer the axle GAWRs will total about 90% of the GVWR; on a fifth wheel about 80%.

I seem to recall you have a modest sized travel trailer, so that weight number looks way large.  Is that 16,040 the trailer only or combined trailer and tow vehicle?  The combined rating is known as GCWR, not GVWR, and is an attribute of the tow vehicle.  GCWR is NOT the sum of tow vehicle and trailer GVWRs and in fact has little to do with those numbers.
 

FastEagle

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longhaul said:
JFY.....GVWR isn't used as any legal definition  to determine a vehicle "legal wet weight" as you call it.....however your weights look good
  I keep a scale ticket of the front and rear axle weights for the car...all my trucks and all the trailers empty axle weights.

That depends on who it may concern. For the vehicle builder it's a weight used in vehicle certification. They MUST list it as the maximum allowable weight for a vehicle. 
 

MtnGoat

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Gary RV_Wizard said:
I seem to recall you have a modest sized travel trailer, so that weight number looks way large.  Is that 16,040 the trailer only or combined trailer and tow vehicle?

It is modest Gary. A 25' Springdale 5er.  The truck GVWR is 10,000 and the trailer 7,920. 
My total scale weight is 16,040 full fuel & water.  Not including passengers and food stuffs.
 

Gary RV_Wizard

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Thus you should be comparing the combined weight of 16,040 to the truck GCWR.  Neither the truck GVWR nor the trailer GVWR are related in any way, so the 17,920 combined GVWR is irrelevant.  To put it another way, GCWR is NOT the sum of the GVWRs. It's a separate number in its own right, established by the truck design engineers and part of the truck specification.
 

MtnGoat

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Interesting I found that to be 16,000 on this site, https://auto.howstuffworks.com/auto-parts/towing/towing-capacity/vehicle%20/gcwr7.htm

Then another site offered this bit of information.
......when the trailer in the truck-trailer combination has a GVWR of 10,000 pounds or less, the CDL requirements allow for a greater GCWR for both the truck and trailer without requiring a CDL. For example, a truck with a GVWR of 26,000 pounds or less can tow a trailer with a GVWR of 10,000 pounds or less and not require the operator to have a CDL under federal requirements. However, CDL requirements mandate that the truck and trailer GVW not exceed 26,000 pounds and 10,000 pounds, respectively. In short, the truck and trailer cannot be overloaded.

http://www.ntea.com/NTEA/Member_benefits/Industry_leading_news/NTEANewsarticles/The_role_of_GVWR_and_GCWR_in_specifying_work_trucks.aspx


 

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grashley

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You need more numbers from the scale.

With the FW connected but Only truck tires on the scale - this is the weight of the truck, and should be less than truck GVWR, or 10,000#

With truck and FW on the scale - this is GCWR (gross Combined Weight Rating) and is established by the truck manufacturer.  WHAT you are towing does not matter.

Weigh the truck without the FW connected.  The difference between this and the first weight is the FW pin wt.  The difference between this and the second weight is the weight of the FW.

The difference between the GVWR weight and GCWR weight is the weight on the FW axles.

For example, if the first weight was 9900# and the second wt was 16,040#, and the truck only was 7800#, then the truck at 9900#  is under the 10,000 GVWR, the pin wt is 2100#  (9900# - 7800#)  and the camper wt is 8240#.  (16,040# - 7800#).  The FW axles are carrying 6140#  (16,040# - 9900#).

Hope this helps.
 

Gary RV_Wizard

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I've written an article on the Where, Why and How of weighing an RV trailer.  I was paid to write it for another website so I can't put it in the Library here, but you can view it at https://vehq.com/weigh-travel-trailer/
 

MtnGoat

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Nice article. I used some of your info to make my calcs and a spread sheet to share.

Not much of an Excel user. So the formulas are really basic.

Comments or changes are welcome.
 

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FastEagle

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MtnGoat said:
Nice article. I used some of your info to make my calcs and a spread sheet to share.

Not much of an Excel user. So the formulas are really basic.

Comments or changes are welcome.

Starting on page #47 in the reference, you'll find just about all the information necessary for weighing your rig. Don't let the document heading fool you. Page #47 is in chapter #4 which is all about RV tires, all RVs.

https://www.ustires.org/sites/default/files/CareAndService_PassengerAndLightTruckTires.pdf
 
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