MFG Ratings what are the limiting factors

[Dog_Trainer]

I know this post will not change the MFG rating no matter what is stated that is not the point. The point is that there are many after market products out there and in the end they do not change what the MFG sticks on the door. But why ?
So what is the true weak link in any rating. Which component or components provide the drawback.?
I suspect that it may be possible to add a component or components and that if the numbers were crunched taking the new component into consideration, that the rating may change.
Most tow Vehicles fall short in the carrying capacity rating. You can pull a great deal of weight but the cargo carrying capacity is met or exceeded long before the GCVW is close. I will list a couple of items that I can think of.
1. The tires that are put on many smaller P/u are P metric tires they make these cushy looking grocery getters ride more car like. So one limiting factor could be the tires and don't forget those 20" rims that they all have to have now. So with a stronger Rim and E rated tire what changes. Well nothing really because the Mfg rating does not change. Right.
2. Shocks
3. Springs
4. Axles
5. Trans cooler
6. engine in some cases
7. Cooling capacity
The whole suspension thing has so many after market components that you would think you could tow or carry about anything.
In the end it is about a truck that is engineered as a complete unit and the MFG does not list the limiting factors. In the case of the F150 with a max tow pkg., the rating of Carrying capacity goes up to around 2,000 lbl from about 1500 lbs with just the HD tow pkg. So what are the other factors of weight and tow ratings. One could become convinced that they can exceed the sticker ratings if the change components.

[kaydeejay]

john&bet wrote:
I think it better to ask the engineers at the OEM manufactures.

Manufacturers are required to certify vehicle safety and emission performance to comply with many Federal requirements before they can be offered for sale.
Compliance tests are performed on a loaded vehicle. Marketing sets a target vehicle capability. Engineers design the vehicle to meet those criteria when possible, which establishes the GVWR and other ratings.
This is the weight at which they are tested.
Will the truck fall apart if you exceed ratings by 5#? No, but they have to draw a line somewhere.
If the user loads the vehicle beyond those certified ratings, then it will likely let the Manufacturer off the hook for certain warranty and liability situations.
(BTW, many years ago I was responsible for those certification labels that go on the door of US sold vehicles for one of the "Big 3" so I know a little about what is behind the numbers).

[rhagfo]

john&bet wrote:
Another thought or take on it. Would you knowing fly on an overloaded aircraft? I spent 20 years in aircraft maint. on four different airframes. Of those, 3 have been retired. The one still flying was designed in the '40's and last built in very early '60's.

Every time I fly!
Most airliners can't land as loaded for takeoff!

[rhagfo]

Old-Biscuit wrote:
Mfg. published MAX TOW Rating numbers are joke--magical numbers.
Long before that number is reached the tow vehicles ratings will be reached/exceeded.

First number usually reached is 'actual payload' capacity (GVWR minus Actual weight)
Second number usually reached is OEM Rear Tire Max Load Ratings
Third number usually reached is GVWR
Fourth number usually reached is RAWR


Unless 'recertified' GVWR is GVWR
RAWR......depends on which rating you choose to go with. Vehicle mfg. rating OR the AXLE mfg. rating. Axle mfg.s is typically much higher
Rear tires can be upgraded to higher load rated tires.

Personally I am over trucks GVWR, right at Rear Tire Load Rating and barely under trucks RAWR.
I could change out tires to higher ratings but I know my weights and am comfortable with being at max load.

BUT one more 'bag of stuff' in truck or 5vr and I could be a hazard on the road :B

Wow, Old-Biscuit you make me feel so much better!!

I am well over GVWR, but at least 600# under on both axles, and with factory over sized tires (265/75-16E) have 3,660# of spare tire capacity! I look to have 1,400# of tire capacity to spare on the rear axle.

[john_bet]

Another thought or take on it. Would you knowing fly on an overloaded aircraft? I spent 20 years in aircraft maint. on four different airframes. Of those, 3 have been retired. The one still flying was designed in the '40's and last built in very early '60's.

[spoon059]

Too many variables to say for certain. You upgrade the tires, but can your wheel studs handle the increased weight? You upgrade the suspension, but can the frame handle the weight?

I know that all trucks are tested to failure and the decision about ratings is made at that point. What that failure is... we don't know. All we know for certain is that truck manufacturers want to be able to give higher and higher numbers for payload and towing... but they also want to keep the numbers low enough that it keeps warranty costs down and reliability up.

Chances are that you are safe at 20% over payload ratings (300 lbs in my case)... but is it worth it? That extra weight, over time, will cause increased wear and tear and make the truck less reliable more quickly. If you constantly need an additional couple hundred lbs of payload then you need a heavier duty truck.

[Old-Biscuit]

Mfg. published MAX TOW Rating numbers are joke--magical numbers.
Long before that number is reached the tow vehicles ratings will be reached/exceeded.

First number usually reached is 'actual payload' capacity (GVWR minus Actual weight)
Second number usually reached is OEM Rear Tire Max Load Ratings
Third number usually reached is GVWR
Fourth number usually reached is RAWR


Unless 'recertified' GVWR is GVWR
RAWR......depends on which rating you choose to go with. Vehicle mfg. rating OR the AXLE mfg. rating. Axle mfg.s is typically much higher
Rear tires can be upgraded to higher load rated tires.

Personally I am over trucks GVWR, right at Rear Tire Load Rating and barely under trucks RAWR.
I could change out tires to higher ratings but I know my weights and am comfortable with being at max load.

BUT one more 'bag of stuff' in truck or 5vr and I could be a hazard on the road :B

[goducks10]

Without limitations guys would overload their trucks and things could wear out prematurely causing warranty issues for manufacturers. Put a limit on what the truck can handle without wearing out before the warranty is up and the manufacture comes out ahead.

[BenK]

X3

Add that it may not be that bolt, bracket, frame section (they are
now made up of several sections on most OEMs) etc

It can be the stopping distance, the ability to get the GCWR going
from a dead stop...several times...at the worst ambients (incline,
altitude, humidity, temp, etc, etc)

It can be the MTBF for 'that' model line

It could be the tolerance variation & stack up on the worst case
scenario for in house components/sub-systems/etc to out sourced
products

and a big ETC...

Dog Trainer wrote:

fla-gypsy wrote:

john&bet wrote:
I think it better to ask the engineers at the OEM manufactures.

This is really the issue. Only the engineering design team know for sure and they aren't divulging that information. It could be as simple as the shear rating of the bolts used to hold it together but you cannot with 100% certainty know that. Many choose (unwisely IMO) to ignore the ratings and just do what they want. I'm not one of them since I don't know what exactly is the limiting factor and I value the continued good service my truck provides me and seek to keep it that way.

I too think this is the real answer. We do not know where the weak component is and the Mfg ain't saying.

[Dog_Trainer]

fla-gypsy wrote:

john&bet wrote:
I think it better to ask the engineers at the OEM manufactures.

This is really the issue. Only the engineering design team know for sure and they aren't divulging that information. It could be as simple as the shear rating of the bolts used to hold it together but you cannot with 100% certainty know that. Many choose (unwisely IMO) to ignore the ratings and just do what they want. I'm not one of them since I don't know what exactly is the limiting factor and I value the continued good service my truck provides me and seek to keep it that way.

I too think this is the real answer. We do not know where the weak component is and the Mfg ain't saying.

[fla-gypsy]

john&bet wrote:
I think it better to ask the engineers at the OEM manufactures.

This is really the issue. Only the engineering design team know for sure and they aren't divulging that information. It could be as simple as the shear rating of the bolts used to hold it together but you cannot with 100% certainty know that. Many choose (unwisely IMO) to ignore the ratings and just do what they want. I'm not one of them since I don't know what exactly is the limiting factor and I value the continued good service my truck provides me and seek to keep it that way.

[Bedlam]

The same components are used in multiple configurations to reach certain market segments. My previous truck could have a GVWR between 9600-11,500 using the same components because you could get to the same combination through different options. I believe marketing is number one driver of these ratings followed by warranty. Actual component specifications are derated to fit the needs of the above.

[john_bet]

I think it better to ask the engineers at the OEM manufactures.

[kcmoedoe]

I have loaded my GMC way over the capacity and I have towed way over the capacity and never has the thing fallen into a million pieces. I believe another poster got it right, it is a liability thing. BTW, what do you want the manufacturer to do, have a computerized system that automatically detects and recalculates the capacities and displays them based on what 100 million or so modifications, adjustments and just plain stupid things people do to their rigs?

[Dakota98]

Dog Trainer :

I think you make a very valid point. Doesn't really make sense, does it?

For the most part, I believe it has more to do with a manufacturers "limits of Liability"

All components "installed by the manufacturer" at the time of build enter into that arena.

Anything added as "aftermarket" are at the owners option & liability.

A simple example, my truck is rated at 5320# GVWR "as built". The front & rear axles, combined are at 6166# & those figures are based upon the weakest ling of the entire suspension system. I have added helper springs and changed to 108 rated tires only. When loaded with my ATV in the back & hooked to the TT (550# tongue weight), a full tank of gas, & with me in the drivers seat I'm at 5650# (Cat Scales). It handles like a dream.

Another thing & I hesitate to mention this because the "weight police" will send the Sheriff to my door.
My truck "as built" has two ratings for GCWR.
The first is 9,200# with 3.55 gears (which is what I have)
The second is 10,500# with 3.92 gears

I have a WDH & anti-sway. My rig never flinches when a semi passes me & I never go over 60mph.

I'm at 10,620#, TT loaded - NO water. I put water on board when I'm a few miles from destination.
I have had absolutely no issues with handling. NONE
I realize this is putting a strain on the transmission, yes, I have a cooler. When pulling I disengage the OD.

[rhagfo]

I would think it varies from TV to TV!
I have a rear axles rated at 10,000# by Dana, but Ram gave it a rating of 6,084#, which is the capacity of the stock LT245/75-16E tires. This truck was ordered with a Camper Package that included bigger springs and larger tires the LT 265/75-16E's that cam on it have a per tire rating of 3,415# so the VIN sticker should have been updated to reflect the LT 265/75-16E's as stock tires, and a rear axle of 6,830#, but Ram chose not to do this.
The next thing would be springs, here again, larger springs, no change.

This is all on my 2001 RAM 2500.

Now days most trucks have many GVWR depending on options, and it is reflected in the VIN and Payload sticker.