GVWR and Tongue Weight

jbrack wrote:
so what I'm getting at is tire rating. By transferring 2,000 pounds to the king pin I am reducing the weight on the trailer wheels by 2,000 pounds, Correct? or am I not understanding this

You will be reducing the weight on the trailer axles some but only because the pin is farther forward than the landing gear. Arms and moments and all that stuff. Basically you are just moving the weight carried by the landing gear to the pin, the axle weight won't change that much.

Another thing to consider with tires is that side to side loading can be very different. My left side tires are carrying 600 lbs more than the right side empty and probably closer to 900 lbs when loaded because most of the inside storage is on the left side.

jbrack wrote:
Does the tongue weight applied to the fifth wheel hitch reduce the weight of the loaded trailer? In other words, if my loaded trailer weights 12,000 lbs while not attached to my truck but when I hitch up there is 2,000 lbs of tongue weight, is my GVW of the trailer reduced by that 2,000 lbs making it now weigh 10,000 lbs?

When the trailer manufacturer certified your trailer, they were required to present figures that insured the GAWR weights shown on the vehicle certification label would safely carry the loaded trailer. To do that they must publish a hitch/tongue weight. That published tongue weight, when added to the trailer’s certified GAWR weights must not be less than the certified GVWR.

After the trailer’s first sale, the management of the hitch/tongue weight becomes the responsibility of the owner.

Mismanagement of that weight is probably responsible for many of the early tire failures on RV trailers. Original Equipment tires are very often providing little, if any, load capacity reserves. Any un-level connection between the tow vehicle and the trailer can cause axle overloading on multi-axle trailers. Without an occasional trip to some scales we just don’t know what our axles are carrying. Nor what load is being carried by the tow vehicle.

You will also note that most 5th wheels have axle ratings that equal less than the trailer GVWR. Like two the 7K axles under our 16K GVWR BH3575el. Chris

4x4ord wrote:
The dry weight of my fiver is about 13800. 11,500 lbs on the axles and 2300 lbs on the pin. When I unhook from the truck I have 3000 lbs on the jacks and 10800 on the trailer axles.

There we go, someone that understands levers. The placement of the land gear means that they will always hold up more weight than the measured pin weight when the landing gear is retracted.

I guess younger people never had teeter totters in their school yards, or took physics classes in school.

Chris

It sounds like jbrack is trying to figure tire load to GVWR.

My thinking is use tires that are rated to at least the maximum GVWR, then when the truck or landing gear has some of the weight it is giving me a little cushion of safety.

4x4ord wrote:
The dry weight of my fiver is about 13800. 11,500 lbs on the axles and 2300 lbs on the pin. When I unhook from the truck I have 3000 lbs on the jacks and 10800 on the trailer axles.

Do you really want to get into physic and vector algebra to explain why this happens? This is why if you are close to going over the TV GVWR it is smart to move stuff from TV bed to the 5er basement.

The dry weight of my fiver is about 13800. 11,500 lbs on the axles and 2300 lbs on the pin. When I unhook from the truck I have 3000 lbs on the jacks and 10800 on the trailer axles.

jbrack wrote:
Does the tongue weight applied to the fifth wheel hitch reduce the weight of the loaded trailer? In other words, if my loaded trailer weights 12,000 lbs while not attached to my truck but when I hitch up there is 2,000 lbs of tongue weight, is my GVW of the trailer reduced by that 2,000 lbs making it now weigh 10,000 lbs?

Complicated ain't it? Thing is. You trailer axles never carried all the weight of the trailer. That is why they are normally rated for less than the GVWR. The pin weight is always either on the truck, or on the front supports. So if your trailer weighs 12000lb, but you have 2000lb of pin weight. You trailer tires always carry 10,000lb. even when not hooked to your truck.

Your tires are only supporting the #10000 axle weight. The #2000 pin weight is either on the jacks or the pin.

If you weigh them all together, you get the #12000 (front jack weight and axle weight)

Mitch

jbrack wrote:
so what I'm getting at is tire rating. By transferring 2,000 pounds to the king pin I am reducing the weight on the trailer wheels by 2,000 pounds, Correct? or am I not understanding this

Well not exactly,
the 2000 pounds was supported by the ground via your front jacks, before you hooked up to the trailer.
The 10K on the axles before you hooked up, is still the same 10K on the axles after you hooked up.
2K+10K=12K. The weight of the trailer never changes