Weight calculations for dummies

anaro wrote:
You need to know more about your trucks capabilities than just my truck can tow x lbs. (I learned this the hard way). Most TV are limited by their payload. To find out your TVs true towing capacities then you need to go weigh it. Load the tv up with all occupants, pets, and cargo that will be in it when towing plus a full tank of fuel and then go weigh it at a local scale (www.catscale.com). Weigh each axle on a separate scale pad so it will give you a breakdown of front and rear axle weights individually and a total weight. Take the total weight and subtract it from your Trucks gvwr to get your available payload. Take the scaled Truck weight and subtract it from your Truck gcwr to get your adjusted towng capacity.

Now understand you will never tow an unloaded or dry trailer. Those numbers are somewhat irrelevant. You can either add the amount of weight of cargo you will tow to the dry weight (this is heavier than you think as most add 1000-1500 lb of gear) or simply use the tt gvwr to do your calculations. (for your purposes do all weight calculations using TT gvwr). Next understand that the tt loaded tongue weight needs to be subtracted from your available payload. The loaded tongue weight is typically 13-15% of the loaded tt weight. The dry tongue weight doesn't even include propane or battery. Also anything placed in the trailer in front of the axles will add to your tongue weight. For your purposes 13-15% of the TT gvwr will be an easier calculation to figure out.

An example here (totally made up numbers from fictional vehicle).... curb weight on scale loaded with passengers and gear: 8500 lbs. TV gvwr 10000 lbs. you have 1500 lbs available payload for a loaded tongue weight. On the fictional trailer, there is a dry weight of 5700 lbs and gvwr of 7700 lbs. Said trailer actually scales in at 7000 lbs loaded. 15% of the loaded (7000 lbs) weight is 1050 lbs. Fictional truck may also have a door sticker that says occupants not to exceed 1700 lbs but with pets, passengers and gear you are down to 1500 lbs available payload.

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.Basically that is because Ford does not know how or what you will add to the truck after purchase. Load it up like your going camping and go to the local scales for an accurate ready to travel 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.

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.Fords are notorious for being heavy, so I would guess your actual weight is 8000+ pounds. What you actually got was front axle plus some percentage or rear axle weight. There is simply no way to balance the truck weighing each axle independently. You need to read the total weight with both axles on the same platform.

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?Like axle ratings for each axle, the tires have a rating placed on them by the tire manufacturer. That is the maximum that the tire is certified to carry. Generally speaking the sum of the four tires will equal the vehicles GVWR.

Any idea what the truck weighs?

How do you use the axle weight ratings. In reality, you don't. Axle ratings are the maximum weight ratings placed on that single component by the axles manufacturer. Remember Ford does not make the axle, they buy a semi finished component from an outside supplier. That supplier makes the axles with XXXX pound 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 axle the other night, there is virtually no capacity.

Your help would be most appreciated.

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.