The front axle rating (GAWR) of the new 2008 F250 is 5250 lbs; the rear axle rating (GAWR) is 6200 lbs. If I add those together I get 11,450 lbs; but the max GVWR is 10,000. It's similar with my 1996 F250; front GAWR=3690 lbs, rear GAWR=6084 lbs, but total GVWR=8600 lbs. Why is that so?

 

my guess would be that that is the absolute max weight rating for the axles, and they want a bit of a safety buffer there. also, it provides enough room for different ratings. remember some places register by gvwr. so the different ratings let people choose the right rating for the applications they will use the truck for.

 

It tells you that something other than the axles is the limit for the GVWR.

 

OK, GAWR is how much you can load the axle. Truck weight on the rear axle plus your load should not exceed the GAWR for the axle. Simple enough concept.

GVWR is total weight of the truck and contents. But....there is a hitch. If you load 6200 pounds on the rear axle, you can't load the 5250 on the front axle or you will exceed the GVWR. So, you can load up one of the axles to max GAWR, but not both axles.

 

What might that other "something" be, Mark?

 

Well, Redford, if GAWR really is the amount of weight you can put on an axle, and if the GAWR for the front axle is 5250 lbs, why then can I not put 5250 lbs on the front axle if I have 6200 lbs on the rear axle? I think Mark is on to something, but he hasn't said what exactly. Please help me understand this simple concept, instead of just musing on how simple it is.

 

I don't know for certain. It could be a frame thing, it could be brakes (that's my guess), but I don't really know what it is. It just seems to me that if the GVWR is less than the sum of the GAWRs that something else is the limit.

 

GAWR is static weight on the front or rear axle. GVWR is static weight on the entire truck. You can load the rear axle of the example truck to 6200 pounds, but if you did this and loaded the front axle to 5250 pounds you'd exceed the GVWR. Why?

The axle rating is just weight pressing down. The GVWR rating takes into account the ability of the truck to support AND move the load safely. The two ratings have nothing to do with each other.

You also need to consider the GCWR when factoring it all together. I've seen trucks that the GCWR isn't exceeded (truck + cargo + trailer weight), the GVWR is OK (truck plus cargo plus trailer tongue weight on entire truck) but the GAWR is exceeded (truck + cargo + trailer tongue weight on rear axle).

 

My money is on wheels, based on materials and ratings; tires, based on air pressure and ratings; axle ratios.

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If I remember right, I think the 10,000lb GVWR is a no cost option to allow a person to buy whatever spring setup they want, and still register the vehicle as 10,000lbs in order to get cheaper insurance/registration in some states.

 

I have a friend that uses the front of his truck to move trailers and some of his equipment. He is a receiver in the front he works in limited space. So he has found that pushing it from the front in some areas is easier than backing it in. And some of this stuff. He has is pretty heavy.

 

+1, Redford. Weight shift under braking, brake system capacity, etc. are figured in.

Later...
Brewster...

 

Does it have anything to do with the trucks being derated to avoid certain classifications or something?

I know its an extreme example, but the CXT gvwr was marked as lower than it could be in order to make is legal to drive with a class C license. Just a thought...

 

Like Redfrd said, static weight vs. dynamic loading. Load your axles to the max and then go over a speed bump at 5mph. Something's gonna give under a dynamic load. Momentary loads during driving can be huge compared to static loads.

 

Not only do all the other components (frame, springs, tires, brakes, performance, etc)figure into the equation, but if the GVWR was equal to the GAWR, then in order to load to max weight, you would have to get the load perfectly balanced between the front and rear axles - and that just ain't gonna happen.