Why doesn't the math work?

[Abby_Normal]

I have received a lot of education from this forum, but I am back with another question. I have learned that my TV payload is 10,000 lbs. and that the GCWR is 23,500 lbs. The TV with passengers and EXTREMELY LITTLE cargo is 8280 lbs. This leaves 15,220 lbs. for trailer, hitch, and cargo. If I allow 300 lbs. for the hitch and 1200 lbs. for cargo, I have 13,720 lbs. for trailer, right? Not so fast. If the TV only carries 10,000 lbs. and we weigh 8280, we only have 1720 lbs. left for pin weight. What about the weight of the hitch? If the hitch weighs 300 lbs. we now only have 1420 lbs. left for pin weight. Why do manufacturers sell units as 1/2 ton towable when I can't get the math to work for our F-250 diesel?

[fj12ryder]

Powerdude wrote:
GVWR is a totally made up number, and it only serves a regulatory need, depending on whatever market niche the manufacturer wants to fill, and what paperwork has been filed with regulatory agencies, nothing more.

Case in point, my 2016 F250.

Front axle WR: 5200 lbs
Rear axle WR: 6100 lbs
Tire ratings: 3450 per tire (2 tires per axle adding up to 7900)

GVWR is 10,000 lbs. What combination of the above numbers adds up to 10,000 lbs ? (Hint: using regular math, no imaginary numbers, or multiple dimensions)...

I can't register it for 10,000 lbs in my state, I can only do either 8000 lbs, or 12000 lbs, no other options. I asked the lady at the DMV what would happen if I registered it for 8k, but I was found overweight. She said I'd get a ticket.

Guess which one I registered it for? 🙂

Don't forget that in Missouri you register for your GCVWR, not just your GVWR. So if your total weight of truck and trailer exceeds your license weight you can be ticketed. If you're pulling a 8,000 lb. trailer and you get stopped and checked, you could be cited for exceeding your licensed weight. Prolly never happen, but you never know.

[Slownsy]

Ther is also accelerating from a standing op hill to consider and stopping pover, not only what axle can handle.
Frank.

[Rich1961]

CWSWine wrote:
When people start exceeding numbers I just don't stand the reasoning. Take a F350 with 11,500 GVWR Class 3 truck. A SRW Class 3 truck can have GVWR up to 14,000 pounds. Ram SRW are up over 12,000 lbs. If axle ratings are the real limits why won't Ford be "Best In Class Payload" and use the axle ratings instead of the lower GVWR? Why doesn't Ford follow RAMS lead and raise the GVWR? There must be a reason! Could it be safety or is something else the limits that truck for carrying that weight. Just food for thought.

I can't speak for other states, but in California once you have 11,501 lbs GVWR and higher, and the truck weighs 8001 lbs or more unladen, it is no longer considered a pickup. Even though all pickups are registered commercial here, things change on the registration side of things once you exceed those limits.

Rich

[rhagfo]

CWSWine wrote:
When people start exceeding numbers I just don't stand the reasoning. Take a F350 with 11,500 GVWR Class 3 truck. A SRW Class 3 truck can have GVWR up to 14,000 pounds. Ram SRW are up over 12,000 lbs. If axle ratings are the real limits why won't Ford be "Best In Class Payload" and use the axle ratings instead of the lower GVWR? Why doesn't Ford follow RAMS lead and raise the GVWR? There must be a reason! Could it be safety or is something else the limits that truck for carrying that weight. Just food for thought.

Axles are not the limiting factor in most cases, it is tires and wheels.

The Dana 80 rear axle in my 2001 2500 has a rating from Dana of 11,000#, but the stock tires limit to 6,084# on my VIN plate. This is the same axle they use in the 3500 DRW with a higher rating to go along with the greater tire capacity.

In addition the max on aRam SRW is about 12,000#, 14,000# is the limit on the DRW.

[CWSWine]

When people start exceeding numbers I just don't stand the reasoning. Take a F350 with 11,500 GVWR Class 3 truck. A SRW Class 3 truck can have GVWR up to 14,000 pounds. Ram SRW are up over 12,000 lbs. If axle ratings are the real limits why won't Ford be "Best In Class Payload" and use the axle ratings instead of the lower GVWR? Why doesn't Ford follow RAMS lead and raise the GVWR? There must be a reason! Could it be safety or is something else the limits that truck for carrying that weight. Just food for thought.

[Abby_Normal]

ol Bombero-JC wrote:

Abby Normal wrote:


I have received a lot of education from this forum, but I am back with another question.

WOW!! - TEN pages of "education" for *this* question (so far)!!..:B

Hope you made it past the first page (I didn't) - but.....
hope your question/s have been adequately covered - in depth, LOL.

BTW - *If* you have done that, you will be considered an Associate (or Honorary) Member of the Weight Police...:C

~

Done what?

[ol_Bombero-JC]

Abby Normal wrote:


I have received a lot of education from this forum, but I am back with another question.

WOW!! - TEN pages of "education" for *this* question (so far)!!..:B

Hope you made it past the first page (I didn't) - but.....
hope your question/s have been adequately covered - in depth, LOL.

BTW - *If* you have done that, you will be considered an Associate (or Honorary) Member of the Weight Police...:C

~

[rhagfo]

sdetweil wrote:

wilber1 wrote:
...

I don't pretend to know why manufacturers chose a particular GVWR for a vehicle and I'm not about to make assumptions about how they do. Just because some states may legislate a maximum GVWR for 3/4 tons, doesn't mean all states do and all GVWR's are determined that way. 1T GVWRs are increasing with every new truck that comes out. You can say it is all about bragging rights but the engineering still has to be there to back them up.

because there are laws in each STATE which defines specific vehicle classes.. 10,000 lbs, 11,600 or 11,700, and 13,000

if you want to sell a truck at a low end of the price range and have it used by commercial buyers (biggest volume) its gotta fit in the laws, AND the fees charged match..

duallys in Massachusetts are commercial.., obviously!.. who knew?!..

so, to stay within the law, they out the appropriate sticker on it.

250/2500's have 10,000 lbs limit, 350/3500 srw's go to 11,700. duallys above that, 13,000... cause thats what the state regs say.
have next to nothing to do with the technical content of the vehicle in most cases..

but.. its a nasty 'law' thing.. so, there MUST be consequences somewhere...

The classes are Federal, it is what some States do with those classes is the killer!
You can only assume that most state law makers, don't own an RV!!!

[sdetweil]

wilber1 wrote:
...

I don't pretend to know why manufacturers chose a particular GVWR for a vehicle and I'm not about to make assumptions about how they do. Just because some states may legislate a maximum GVWR for 3/4 tons, doesn't mean all states do and all GVWR's are determined that way. 1T GVWRs are increasing with every new truck that comes out. You can say it is all about bragging rights but the engineering still has to be there to back them up.

because there are laws in each STATE which defines specific vehicle classes.. 10,000 lbs, 11,600 or 11,700, and 13,000

if you want to sell a truck at a low end of the price range and have it used by commercial buyers (biggest volume) its gotta fit in the laws, AND the fees charged match..

duallys in Massachusetts are commercial.., obviously!.. who knew?!..

so, to stay within the law, they out the appropriate sticker on it.

250/2500's have 10,000 lbs limit, 350/3500 srw's go to 11,700. duallys above that, 13,000... cause thats what the state regs say.
have next to nothing to do with the technical content of the vehicle in most cases..

but.. its a nasty 'law' thing.. so, there MUST be consequences somewhere...

[Slownsy]

in Australi GVWR is a legal rating set by manufacturer by what ever means, do not go over or you vill get fined if put on the scales.
Frank.

[wilber1]

rhagfo wrote:

wilber1 wrote:
The weakest component will always determine the limit for the complete structure. Only the manufacturer knows what that is. Eg: you can physically put a 5K brake on a 7K axle. You may be able to carry 7K but you can't stop it, therefore your design limit is 5K, not 7K.

To be rated at 7K an axle needs to have 7K of braking power. The rear axle in my 2001, from Dana has a rating of 11,000#, in my truck, it is rated at 6,084# which is the capacity of the stock 245/75-16E tires (The weakest component). This axle has the same brakes as the 2001 3500 axle rated at a bit over 7,000# so brakes not the limit. My 2001 has a camper package and Optional 265/75-16E tires rated at 6,830# for the pair.
So based on the facts stated above I could consider my axle rated at 6,830# as the Camper Package also includes 3500 springs.
I don't need to as I am still 500# under the stock 6,084# rating.

Isn't that what I was saying? I follow your logic but you can consider whatever you want, your axles are still rated at 6084#. Could that possibly be an issue for you? My guess is no but that's just my guess. It's odd that the higher axle rating wasn't included in a factory package that included the higher rated tires. I also believe your GVWR remains at 8800#.


I was thinking along the lines of 5-6 and 7k trailer axles where the brake assemblies are interchangeable. Replacing a 7k brake with a 5k brake would reduce the axle's capacity to 5k, even though it still has the larger structure and bearings that make it able to support 7k.

I don't pretend to know why manufacturers chose a particular GVWR for a vehicle and I'm not about to make assumptions about how they do. Just because some states may legislate a maximum GVWR for 3/4 tons, doesn't mean all states do and all GVWR's are determined that way. 1T GVWRs are increasing with every new truck that comes out. You can say it is all about bragging rights but the engineering still has to be there to back them up.

[rhagfo]

wilber1 wrote:
The weakest component will always determine the limit for the complete structure. Only the manufacturer knows what that is. Eg: you can physically put a 5K brake on a 7K axle. You may be able to carry 7K but you can't stop it, therefore your design limit is 5K, not 7K.

To be rated at 7K an axle needs to have 7K of braking power. The rear axle in my 2001, from Dana has a rating of 11,000#, in my truck, it is rated at 6,084# which is the capacity of the stock 245/75-16E tires (The weakest component). This axle has the same brakes as the 2001 3500 axle rated at a bit over 7,000# so brakes not the limit. My 2001 has a camper package and Optional 265/75-16E tires rated at 6,830# for the pair.
So based on the facts stated above I could consider my axle rated at 6,830# as the Camper Package also includes 3500 springs.
I don't need to as I am still 500# under the stock 6,084# rating.

[wilber1]

The weakest component will always determine the limit for the complete structure. Only the manufacturer knows what that is. Eg: you can physically put a 5K brake on a 7K axle. You may be able to carry 7K but you can't stop it, therefore your design limit is 5K, not 7K.

[rhagfo]

Me Again wrote:
Most front 4x4 axles are a size or three smaller than the rear axles, and could never carry the same weight as the much larger rear axles. Most now also have coil springs in the front with softer ratings to provide a quality ride.

So lets look at my 2015 3500 SRW SB 4x4.

GVWR 11,700
Front GAWR 6000
Rear GAWR 7000

Not much in truck and front axle is 4900.

With Fifth wheel almost ready to Arizona trip
Front 5120
Rear 6620
Truck 11,740
Trailer 12,780
Combined 24520

So I can not by the book use the full rear GAWR without going over the GVWR or getting to the 5th wheel tow rating of 17,050 pounds. Our trailer has a 16K GVWR and is weighing around 15780.

So the same RAM truck with long bed has a 12,300 GVWR. Tires, axles, brakes, springs, etc are all the same, except it weighs more with the longer frame and bed. So did they just set the GVWR higher to account for the heavier truck???

I don't thing I will worry about it. Washington State licensed it at 12K and I could pay a little more and license it at 14K. If I licensed it at 14K and carefully loaded the front axle to 6K and rear to 7K totaling 13K, I would be legal based on the licensed weight.

And we have not even talked about the Federal bridge weight laws.

There are NO standards on how manufactures come up with GVWR. If GVWR was a binding number then there would be standards set on how it is determined. Ford will sell you a 3500 with a 10K GVWR for areas that restrict vehicles over 10K.

Chris

Well at least you need to work at it to exceed GVWR! :B The fact that your GVWR is 90 percent of your axle ratings, makes it a bit harder. Remember back to your 2001.5 where the GVWR was only 78 percent of the axle ratings!!! :S

Remember these numbers;
Front GAWR 5,200#
Rear GAWR 6,084#
GVWR 8,800# :R

So the TV with or without the 5er is right at 4,500# on the front axle so that in reality that leaves me 4,300# that I can carry on my rear axle before exceeding GVWR. Take about 3,000# basic weight on the rear axle and I am left with 1,300# of payload to carry my 5er.
Well I will let you guess the rest , I am 500# under the rear axle capacity. I have added nothing to the rear suspension other than a a full set of Bilstein 5100's. The TV is equipped with the Factory Camper package, but in 2001, that didn't change the GVWR.