Weight calculations for dummies

Seattle Lion wrote:
I have read all of the threads on GVWR, tongue weight, etc. and I am still confused. Since I am an engineer, I suspect it isn't the math that bothers me. After a lot of painful reading, writing, and calculating, we determined that my Ford F150 was going to be over GVWR by a few hundred pounds. So, I traded it for a new F350 Diesel. I know it has the capacity. What I can't do is figure the numbers.

According to the door sticker and the window sticker, the truck has the 11,500 lb option. The door sticker says we have a 11,500 lb GVWR. So far so good. Nowhere on the sticker or elsewhere on ford data sheets is there a value for the truck's weight. On the wheel and tire sticker, it says that max load for the truck is 3,500 lbs. I assume that is based on the capacity of the tires (SRW model). I still don't know what Ford says the vehicle weighs. It is based 0on the weakest link in the entire build. It COULD be tires but not very likely, more likely it's frame, axles or wheeles since it's very easy to maximuze tire loads by going to a more capable tire size. Other items that come into play are brake horsepower, engine cooling capacity and a few other things. Your empty weight would be the GVWR less the payload (11,500 - 3500 lb.) or 8,000 lb.

We went to a closed state weigh station the other night. The scale (there are two platforms about 40 feet apart) isn't big enough on a single platform to hold all four wheels. So we weighed the front and back wheels separately. Front weighed 5,460 and the rear 5,300. It makes no sense that the truck with just us in it weighs 10,700 lbs. That would give us less than 1,000 lbs load carrying. Also, even though I am not a mechanical engineer, I am pretty sure that weighing front and back separately and adding the results does not give true weight. An f350 can't weigh 5 tons! I am guessing it should weigh between 7 and 8,000 lbs. When you weigh only one axle it STILL includes part of the weight on the other axle. There is some overlap when weighed that way.

There are lots of numbers on the stickers and on ford's spec sheet (Ford Truck Specs).

We will look for a bigger scale. In the meantime, there must be a way to get a reasonable estimate of what the truck weighs.

What does the 3,500 lb capacity number on the tire and inflation sticker mean? Is it a truck spec or tire capacity? MOre to it than that. As mentioned earlier it is the maximum weight of the weakest component which is not likely to be the tires. You can get the maximum load rating of your tires from the side wall and multiply by 4 to get the TIRES maximum weight.

Any idea what the truck weighs? Yes 11,500 lb. minus 3500 lb. paylod or 8,000 lb.

How do you use the axil weight ratings. I assume to calculate load, you first need to know what weight the truck puts on the axil and then the difference is the capacity (like for a 5th wheel). If you go by the readings we got when weighing each axil the other night, there is virtually no capacity.

Your help would be most appreciated.