Need GVWR/Load Information

[Crunch]

I'm going to be hauling a load of live shrimp about 800 miles, from Texas to Alabama. The Owner's Manual lists the GVWR at 6400lbs. The shrimp will be in two "totes"--containers molded to a pallet-type base, that contain water to keep them alive. We are estimating that the weight of the two totes, filled with water and shrimp plus an oxygen tank will be right at 5,000lbs. I'm about 160lbs and the gear I pack will be less than 100lbs. So we're talking a maximum of 5500lbs. total weight, plus the truck itself. The totes measure 4'x4' each, so they will pretty much fill the bed. How do I calculate the GAWR (3300lbs front, 3600lbs rear) for both the front and rear axles, and am I within the ratings of the truck, considering it's a 2500?



Thanks.

 

[KCJackson]

Your curb weight is 6400, not the GVWR - that is 9000. You are going to be <B>way</b> over limit if your load is 5000 pounds plus yourself and some gear... you're going to gross somewhere around 12,000 pounds which, considering all that weight will be in the bed, will actually overload your rear tires as well.



Safer suggestion: get a trailer for the shrimp load - you can safely tow up to 13,000 pounds with your truck.

 

[Hoefler]

How tall are the totes?? If they are the same containers they use to transport live fish for stocking, they are 4' tall. If so, each tote will weigh over 4,000 lbs each!! Do the math, width x depth x height x 7. 5 ( gallons per sqft ) x 8. 64 ( water weight per gallon ) = your total weight. This the weight of the contents, you will have to add the weight of the container.

 

[Crunch]

Your curb weight is 6400, not the GVWR - that is 9000. You are going to be <B>way</b> over limit if your load is 5000 pounds plus yourself and some gear... you're going to gross somewhere around 12,000 pounds which, considering all that weight will be in the bed, will actually overload your rear tires as well.

You're right on the main point here. I misread the Owner's Manual regarding the 6400lb figure. They were using that as an example. I checked the sticker on the door and found that the GVWR is 9000lbs, as you stated. GAWR-F is 4750lbs, and the GAWR-R is 6000lbs. I'm not sure the curb weight is 6400, though. I think these trucks weigh in at about 7400lbs on their own. Either way, this is definitely a trailer job.

How tall are the totes?? If they are the same containers they use to transport live fish for stocking, they are 4' tall. If so, each tote will weigh over 4,000 lbs each!! Do the math, width x depth x height x 7. 5 ( gallons per sqft ) x 8. 64 ( water weight per gallon ) = your total weight. This the weight of the contents, you will have to add the weight of the container.

I think we're talking about the same totes, but those are the outside dimensions. Keep in mind that there is about 6" of foam insulation on the sides and bottom that reduce the inside dimensions, plus the pallet bottom that reduces the overall height of the container. But they are too heavy for the bed of the truck, that's for sure. I appreciate the help on this. But I'm also still curious as to how you calculate GAWR for the front and rear axles when you load the bed. How do you know what % of the load is carried by the front axle vs. the rear axle?

 

[BHolm]

Driving it across a scale is the only way to know exactly where the weight is. Adding loads to the bed doesn't generally add much weight to the front axle though.

 

[Hoefler]

But I'm also still curious as to how you calculate GAWR for the front and rear axles when you load the bed. How do you know what % of the load is carried by the front axle vs. the rear axle?[/QUOTE]





Rule of thumb is 30% front, 70% rear is considered ideal.

 

[klenger]

% of load on each axle depends on where the center of gravity of the load is. If the CG is right over the rear axle, then 100% of the weight will be transfered to the rear axle. If the CG is 1/2 way between the axles, the 50% will be on the front and 50% on the rear. As an example, lets assume that the wheelbase is 150" and that the load is 30" forward of the rear alxe. The load on the rear axle is 120/150 * load weight and the load on the front axle is 30/150 * load weight. Hope this helps.

 

[Crunch]

% of load on each axle depends on where the center of gravity of the load is. If the CG is right over the rear axle, then 100% of the weight will be transfered to the rear axle. If the CG is 1/2 way between the axles, the 50% will be on the front and 50% on the rear. As an example, lets assume that the wheelbase is 150" and that the load is 30" forward of the rear alxe. The load on the rear axle is 120/150 * load weight and the load on the front axle is 30/150 * load weight. Hope this helps.

I think that's exactly the formula I was looking for. Thanks. So, as an example:



I measured the wheelbase at 160". The bed extends 42" past the rear axle, leaving 54" to the front of the rear axle. Assume the payload is on 2 4'x4' pallets (I'm excluding the driver's weight for this example) and weighs 1000lbs total. That would place the CG a distance of 6" to the front of the rear axle, because the pallets being equal in size and weight put the CG at the midpoint between the pallets (42" of the 48" pallet sit on or behind the rear axle, 6" in front where the CG is located). Using your formula we would calculate it out as such:



Rear axle: (154/160) * 1000 = 962. 5lbs.

Front Axle: (6/160) * 1000 = 37. 5lbs.



Sound right? If so, that's an interesting differential in weight on the axles. I'm not sure how I would calculate the CG when the driver is included, but I doubt my 160lbs. would affect the equations very much.



Again, thanks for the info. That should be useful for the rest of my life, when hauling payloads.

 

[klenger]

Your calculations look correct. To figure out the impact of a driver, take the answers you got above, add them to the exmpty weight of the truck, and then repeat the process for the driver weight and location of CG.