gvwr - how much due to tires?

certain posters on different RV boards suggest that a dodge dually is capable of far more than the posted gvwr, suggesting that its set based on the load rating of your tires. anyting to this? will higher rated tires
increase your gvwr? thanks,
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Nathan W. Collier
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Nathan W. Collier wrote:

I've often wondered what the formula is that manufactures use to compute GVWR. Or is it that each manufacture has their own formula with a fudge factor depending on market?
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GVWR is easy; GVWR shall be specified by the manufacturer as not less than the sum of: curb weight, dealer installed options weight, occupant mass, luggage.
Another way to look at it each manufacturer determines the maximum acceptable weight limits for each vehicle by considering the combined weight of the strongest weight bearing components (the axles) and the weaker components (vehicle body, frame, suspension, and tires).
So you need to upgrade the body, frame, suspension and tires to safely increase GVWR. Or just move some load to the trailer to reduce GVWR; just keep it within GCWR.
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The problem isn't just modifying the vehicle to increase the GVWR, it is the certification of the increase for liability purposes. It is simply not within the economic capacity of an individual owner. Steve

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certification with who? when i registered my truck at the dmv i licensed it to 18000#.
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Nathan, If you are involved in an accident and the insurance company found you had exceeded the manufacturer's GVWR and in their opinion contributed to the accident, they are no longer liable. You just let them off the hook. Just imagine the hassle with the courts, the lawyers, the cost, your time and possible bankruptcy. Do you think for a single moment that you could defend your self modifications over the factory recommendations successfully? Are you sure you want to do this? Steve

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Steve hit the nail on the head here. If you exceed the manufacturer's GVWR (or GCWR) and are involved in an accident where it can be forensically determined that exceeding manufacturer's weight specifications contributed either to the cause or the severity you will be in some expensive trouble.
Just because you're not a commercial hauler does not absolve you of liability for exceeding vehicle ratings. You can be fined just as severly and shown to be criminally negligent.
When we were investigating the 5th wheel RV thing last month and looking into suitable trucks to haul it with, the Dodge 1-ton dually + CTD was only marginally legal and questionably safe with a 37-footer (Holiday Rambler Presidential Suite) as we would be operating right up against the wall of maximum ratings with virtually no margin for safety. True people do it all the time, even with less truck and get by, but that doesn't make it safe or wise. Idiots are born every day. In our opinion the FL50 was the more appropriate truck for that specific RV.

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On Wed, 8 Mar 2006 12:28:45 +0100, "Steve Lusardi"

Not really true. With most 3/4 and 1 ton trucks there is a lot of reserve axle capacity. The onlu difference between current 3/4 ton and 1 ton SRW P/U's is tires and maybe a extra leak in rear and a lable on door. Chassis is the same otherwise. You have to be a lot more carefull with 1/2 tons as they have a lot less reserve. GVW's like tow ratings are more a product of marketing demands than anything because if you look at a 98 Ford or GM 1/2 P/U you will find that the new models have less spring in the rear than older ones with the same or higher GVW rating. Same with GM 3/4 tons too. To improve ride for sales they reduced spring capacity resulting in a mushier truck at GVW with new models than with older ones.

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Nate:
Nothing can change your vehicles GVWR. It is set by Dodge and cannot be changed. It is certified to FMVSS standards at the time of manufacturer. You "can" do mods that will increase the weight carrying capacity, but this will do nothing to change the GVWR as certified.
The GVWR is determined by the manufacturer through testing and is determined in part by the load carrying capacities of various components. The component(s) that has the lowest weight rating is usually the primary factor is GVWR. Look at it like a barrel with staves of various heights. Even though some staves are quite high, the total water carrying capacity of the barrel is determined by the shortest stave.
Mike
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i guess its time to go look at an F550. :-( i want to add a toolbox utility bed to my truck so that i can have both the utility capability and the slide-in camper while pulling a trailer. i HATE to think that there isnt a cummis powered pickup capable of this in the dodge line....and id have to step up to an F650 to get the cummins in a ford.
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Found this quote:
According to Harry Thompson, chief of the NHSA's Vehicle Crash Avoidance Division, modifying GAWR is much easier than changing the GVWR of a vehicle. Upgrading the axel rating can be as simple as changing out the tires. Modifying the GVWR is a difficult thing to do, requiring modifications such as the addition of frame stiffeners or augmenting the vehicle's structure in other ways, he said.
Looks like the poster to that RV board must have got confused; tires increase GAWR. This link is also worth a read even though it is about adding mods for disabled people it looks like fines would be involved if the mods are not consistent with motor vehicle safety and the Vehicle Safety Act: http://www.nhtsa.dot.gov/cars/rules/interps/files/23087.rbm.html
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thanks. as much as i hate to say it, ill probably have a powerstroke F550 in my yard soon. the F series truck is awesome, but i dont like the powerstroke.
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Nate, there is an alternative. It seems you can have your cake and eat it too, you just have to pay for it. It seems enough folks have decided to plant a Cummins into their Ford to make a little industry of it. Go to www.fordcummins.com and look at that feasibility. Its only money.
FMB
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Or he could go with a Freightliner and choose his power as well as having a better truck than a Ford.
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Max

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now there's an idea. a friend of mine just bought a freight pickup. thing looks sweet (not to mention huge)
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-Chris
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