Are They Meaningless? Tow Limits, Payload and Axle Load

[ROBERT CROSS]

"Overloading" the sticker for ______mi a year is unlikely to fail anything before most folks get tired of their 'old' TV.

Safe loading is another matter.

Disclaimer....ours is 14 SFSG.

Bob
🇺🇸

[dznf0g]

Originally Posted by jaybauman

When I was looking at 5th wheels, pin weights on each of the (larger) units we were considering would have put me over axle limits on my 2015 2500HD Duramax.

I'm not challenging your stability/towability argument, I'm challenging the axle limit statement. How many times do you see a 3/4-ton truck pulling a gigantic toy hauler? I see it frequently (this is Texas, after all) and it does not take a leap of faith to imagine that some of these guys are over axle limits. In my experience, the RV sales guy (replete with 10-gallon hat and 5-pound belt buckle) said to me: "I don't know what axle limits you're talking about. You have a HD DEE-zull; your truck will drag this baby anywhere you want at 75mph...." It would appear that ignorance causes a lot of RVers to intentionally and unknowingly running a lot of these overloaded towing experiments.

On the Duramax forums, there are lots of examples of towing over the limits. The only thing that ever seems to break is the Bosch fuel systems and the complicated emissions reduction systems, and suspension failures are due to incorrect lift kits and the like. The stock axles and suspension components seem to handle these overload conditions quite adeptly.

I might even argue that data suggest the prescribed axle capacities can be routinely exceeded without negative consequences. But this is only an academic exercise for me. As a scientist, I do enough experiments at work. My dear family and expensive rig are too valuable to prove a null hypothesis with.

So here's the thing with those kinds of discussions. The limits are not set solely upon, "this components, which is part of a system, breaks a xx force, so we'll set the load limit at x minus y".

A lot of research goes into how and how frequently the 90th percentile loads and uses the product. From that research, during the design phase of the product there is (in this discussion case) a formula derived like this:

"50% of the consumers of this product tow only x percentage of the miles accrued during its lifetime. Of those who tow, y% tow at 50% of anticipated TWR and Z% tow at 75% of anticipated TWR....and so on with vertical loads, etc.

From all that an algorithm is derived which prescribes that the vehicle will be durability tested at 100% of GVWR (or axle loads or GCWR, etc) 10% of the lifetime cycle, 90% of GVWR 10% of the life cycle, 70% of GVWR 15% of the lifecycle....etc.

(note: these numbers are for illustrative purposes and don't reflect any actual vehicle, and all product lines have different formulas depending on the market they feed into)

So, yes, that 2500 Dmax discussion follows the fact that there is margin, but 2 identical trucks, with identical maintenance and identical environmental operating conditions, pretty much will experience the same component lives. but if one of those trucks operates at 100% GVW over 150,000 miles and one operates at 75% of GVWR over the same 150,000 miles, the first will see more component failures than the second.

Does that all give credence to the camp that says they over spec and don't worry...sure. If that's what they want and they find value in that peace that supersedes their wallet and the inconveniences which accompany a larger capacity truck, have at it. IT DOES NOT MEAN that a properly spec'ed lower capacity truck, ie. 1500, cant do it with most all Airstreams ever built.

[lsbrodsky]

We used to call this killing flies with atomic bombs.....Seems to me that the answer for users is a) follow the manufacturer's guidance on the door plate b) if the vehicle is not rated for towing either see a) or get a vehicle that allows you to follow a).
Larry

[dznf0g]

Originally Posted by lsbrodsky

We used to call this killing flies with atomic bombs.....Seems to me that the answer for users is a) follow the manufacturer's guidance on the door plate b) if the vehicle is not rated for towing either see a) or get a vehicle that allows you to follow a).
Larry

And...therein lies the truth. But, unfortunately, some need to see the sausage made and won't see the issues with overloaded, under spec'd "reinforced" TVs.

And..absolutely why one should buy their trailer, then spec out a TV.

[BayouBiker]

I'll cede to you Jay. I am not well versed on the large fifth wheels or how many of them are over 15,000 when loaded up. My tires are rated just 200 lbs over the axle limit so at the very least I'd think they would experience some tire issues when they overload their 3/4 tons.

[dznf0g]

Originally Posted by ROBERT CROSS

"Overloading" the sticker for ______mi a year is unlikely to fail anything before most folks get tired of their 'old' TV.

Safe loading is another matter.

Disclaimer....ours is 14 SFSG.

Bob
[emoji631]

True, but for that statement to be valid one would have to determine:
1) how much overloaded and which spec is overloaded
2) how many miles a year

[Prettygood]

Originally Posted by dznf0g

1) I doubt you will find this issue of derating on many dealers lots for retail consumption. Typically this is a fleet used option where their needs don't require max GVWR and dozens or hundreds of trucks purchased represent a lot of money relative to any fees and regulations they want to reduce. Kind of wish we didn't muddy the waters with all that.



2) Yes, I do believe that there are hardware differences in the derated trucks. What all is involved with that, I don't know, but whenever there is a configuration restriction, you can bet some component is driving it.



3) Since this derating is the opposite of our true question, relative to GVWR and payload, it's really moot to our discussion, right? We discuss, "can you go over payload and/or gvwr, staying under axle limits....and is there margin on all the specs which we can encroach upon". Correct?



4) I am in the camp, based upon career long periodic discussions as well as observations of product durability performance over time and miles in fleet usage, that the numbers should be respected. I never throw out the safety card, as that subject is way too subjective. I believe the hard and fast number adherence falls in this order of importance:



a) axle load limits & GCWR (equal importance)

b) gvwr load limits & receiver load limits (equal importance)

c) payload limits



Now, that said, I am squeamish that many will take these statements too far. If I am over payload by 100# and at 90ish% of axle capacities, I don't worry. I am comfortable that there is plenty enough of margin to account for that. But 4 or 500#....not so much.

This is exactly what I tried to convey earlier. Being at/close to limits is still in a safe zone of operation for the vehicle. Being well over is dangerous.

I’m still early in my experience (2 years and ~6k miles towing), but not new in my car knowledge. Being at payload, but under on total weight, while using some anti-sway device and driving at 60mph is inherently safe (Airstream use case).

The very in depth conversation on this thread is helpful, and generally civil (if not somewhat meandering). Research and learning help accelerate practical experience.

[DewTheDew]

I would note that I find "payload" on the door jam to be somewhat squishy because 1) it is not always clear what they have already factored into this (full tank? Two occupants?) and 2) because it is pretty difficult to actually measure. I have generally treated that as a derivative number; max GVWR minus what they consider the weight of the truck (using whatever factors they use). I believe that GVWR is the number to follow, while not exceeding any axle values as well. And while I might go over that occasionally with load of gravel, for example, I would be concerned with any organization who told me that number was arbitrary and set up my TV with a trailer that took it deliberately over GVWR.

[dznf0g]

Originally Posted by DewTheDew

I would note that I find "payload" on the door jam to be somewhat squishy because 1) it is not always clear what they have already factored into this (full tank? Two occupants?) and 2) because it is pretty difficult to actually measure. I have generally treated that as a derivative number; max GVWR minus what they consider the weight of the truck (using whatever factors they use). I believe that GVWR is the number to follow, while not exceeding any axle values as well. And while I might go over that occasionally with load of gravel, for example, I would be concerned with any organization who told me that number was arbitrary and set up my TV with a trailer that took it deliberately over GVWR.

Agreed. So, you can easily measure your particular AVAILABLE payload. Since gvwr minus curb weight = payload.
So, what is your curb weight from which to derive available payload.
Put in your truck everything which always stays with truck after the moment it rolled off the assembly line
For me that is;
Stainless running boards
Mudflaps
Tonneau
Spray in bedliner
Momma and me
Emergency road kit
Battery jump pack
Items in center console
Under hood air compressor
Full tank of fuel

Then weigh truck. The weight is now your personal baseline "curb weight" . Subtract that number from gvwr and you have your true personal payload number from which you know how much camping stuff can be loaded, including receiver weight.

[Bobbo]

Originally Posted by DewTheDew

I would note that I find "payload" on the door jam to be somewhat squishy because 1) it is not always clear what they have already factored into this (full tank? Two occupants?)

I may be mistaken, but I think the Federal Government standardized that at full fuel tank, no occupants, no driver.

[dznf0g]

Originally Posted by Bobbo

I may be mistaken, but I think the Federal Government standardized that at full fuel tank, no occupants, no driver.

Right, But IIRC it was SAE who standardized it.

[switz]

I believe RAM includes the imaginary 150 pound driver....

The only numbers that will protect one if in an accident are generated by loading the tow vehicle with all the usual folks and stuff (including the necessary typical drinks and food) and then crossing certified truck scales. That first pass provided the owner with three useful bits of information before talking about towing: actual front axle weight, actual rear axle weight and the actual curb weight of the tow vehicle. Use these numbers to drive the rest of the purchase process.

Checking the tires will reveal their load rating which one compares to the axle ratings to be sure the tires can carry more than the axles.

Take the axle numbers from the scales and subtract them from the respective axle rating. Take the curb weight from the GVW on the vehicle door jams including the decrease in payload yellow stickers from factory add ons. Now look at ball hitch type trailers. Is the tongue weight less than the net payload remaining with a hitch system included in the numbers? What happens with the axle loads as different settings of the weight distribution are tweaked. Lots of scale measurements to determine the correct settings.

The reality of Big Truck scales is that many are not accurate to the individual pound or perhaps 50 pounds. But that is within a reasonable margin of error when the truck weighs over 5,000 pounds or the trailer is a weight that requires brakes.

I made sure the truck never exceeded the axle ratings. It might exceed GVW by a few hundred pounds out of 9,600 pounds. I purchase a higher weight limit plate for 11,000 pounds so I know I will never be "under plated". Over time, the amount of stuff in the truck bed has decreased from a machine shop to those tools really necessary. One generator instead of two and the propane can be supplied by the front port on either Airstream also reduced payload. Factory receiver was replaced with a better built CURT receiver.

The older 33' tri-axle airstreams had a GVW over 11,000 pounds. Now all the longer Classics have the same 10,000 GVW. The sleeper is the close to 1,400 pound tongue weights that could exceed some truck receiver ratings. Always look for the weak link in the tow package.

[F83]

Not enough people bring up liability. If you get in an accident and you are above your stated numbers - you could be in a world of hurt. Denied insurance and lawsuits. Honestly that to me is one of the biggest things to think about.

[Jerrylax]

This seems to be largely an American problem. We rarely see big clunky truvksvin Europe... elsewhere we see old Toyota’s loaded to the hilt as if it were a societal right.

[ITSNO60]

Originally Posted by Jerrylax

This seems to be largely an American problem. We rarely see big clunky truvksvin Europe... elsewhere we see old Toyota’s loaded to the hilt as if it were a societal right.

Is a different ball game in Europe, the ratings are even higher on the exact same vehicles sold here. Tongue weights are lower and speed limits for vehicles towing trailers are lower. Additionally a special license that comes with some education is required to tow most trailers. I am pretty sure the lower limitations placed on vehicles sold in the US have a lot to do with the speeds at which many will travel here.

[BayouBiker]

Lower speeds and trailer designs that don't push the vehicle's back end around so much. They allow for much lower tongue weights without risk of sway.

[jcl]

Originally Posted by ITSNO60

Is a different ball game in Europe, the ratings are even higher on the exact same vehicles sold here. Tongue weights are lower and speed limits for vehicles towing trailers are lower. Additionally a special license that comes with some education is required to tow most trailers. I am pretty sure the lower limitations placed on vehicles sold in the US have a lot to do with the speeds at which many will travel here.

Source?

Speed limits in Europe were generally similar when I lived and worked there. I just looked up the UK and towing speed limits are 60 mph or 70 mph depending on highway classification. Germany has a higher speed limit if your combination is TUV inspected. I recall California is 55 mph. I don’t know which other states have towing-specific speed limits.

No additional drivers licence required in the UK, until you get into commercial vehicles and weights, the same 3500 kg that most light duty vehicles use for an upper tow weight rating.

I think most reduced tow ratings in the US have to do with fear of litigation, since there are differences between the US and Canada as well in terms of tow ratings, and the vehicles and driving conditions are very similar. That can be an issue, but it points to the US tow rating not always being a technically derived rating.

[jcl]

Originally Posted by F83

Not enough people bring up liability. If you get in an accident and you are above your stated numbers - you could be in a world of hurt. Denied insurance and lawsuits. Honestly that to me is one of the biggest things to think about.

What would be the point of mandatory liability insurance if it can be voided at the whim of the insurer? Does this happen commonly for crashes that involve vehicles speeding against posted signs, that insurance is voided?

I think that more commonly, after paying a claim, an insurer could raise your premiums or decline to reinsure you, but they can do that irrespective of your tow rating, it could simply be that they decided you aren’t as safe a driver as they had previously assumed.

[BayouBiker]

You're right icl, insurance generally covers everything but deliberate acts with intended malice, but the degree of protection from liability lawsuits depends on your coverage limits so the risk is still very real. Also risk of being canceled oh having outrageous future premiums is very real as you say.

[jcl]

Originally Posted by dznf0g

1) I doubt you will find this issue of derating on many dealers lots for retail consumption. Typically this is a fleet used option where their needs don't require max GVWR and dozens or hundreds of trucks purchased represent a lot of money relative to any fees and regulations they want to reduce. Kind of wish we didn't muddy the waters with all that.

2) Yes, I do believe that there are hardware differences in the derated trucks. What all is involved with that, I don't know, but whenever there is a configuration restriction, you can bet some component is driving it.

3) Since this derating is the opposite of our true question, relative to GVWR and payload, it's really moot to our discussion, right? We discuss, "can you go over payload and/or gvwr, staying under axle limits....and is there margin on all the specs which we can encroach upon". Correct?

4) I am in the camp, based upon career long periodic discussions as well as observations of product durability performance over time and miles in fleet usage, that the numbers should be respected. I never throw out the safety card, as that subject is way too subjective. I believe the hard and fast number adherence falls in this order of importance:

a) axle load limits & GCWR (equal importance)
b) gvwr load limits & receiver load limits (equal importance)
c) payload limits

Now, that said, I am squeamish that many will take these statements too far. If I am over payload by 100# and at 90ish% of axle capacities, I don't worry. I am comfortable that there is plenty enough of margin to account for that. But 4 or 500#....not so much.

1) I think you will find lots of derated 250/350 class trucks. It wasn’t such an issue IMO until the last few years when ratings climbed past 10,000 commonly. I recall it from F350 ordering years ago, built that didn’t impact F250 models. If you look at your link for the 2500 in 2018 it only applied to the diesel long wheelbase, likely since the other 2500 models were under 10,000. Looking at 2020 heavy duty pickup models, it appears far more common. There are differences by marketing company, for a single manufacturer, even though the vehicles are harmonized across the border. For one manufacturer, in the US the standard GVWR for one model is approaching 11,000, and the 9900/10,000 derate is a no cost option. Look at the same manufacturer in Canada, and the 9900/10,000 GVWR is standard, and the 11,000 gvwr is a no cost option. So most of the trucks on dealer lots have the lower rating. Whether fleets care about the derate can depend on whether they run a mixed fleet, under and over that 10,000 GVWR, or not.

2) I think there may be, but it isn’t necessarily true.

3) My point was that published weight ratings don’t necessarily reflect vehicle maximum capability. They certainly may do so in some applications, and in some categories they absolutely do.

4). My approach is to understand the context for the ratings, and apply them based on that understanding. For example, I always respect tire and axle ratings, at least when towing at public road speeds. I have exceeded them at very low speeds when moving things off highway or on closed roads, on occasion. A large and heavy parade float behind my X5 comes to mind. I always respect GVWR limits when solely hauling, especially if it is a commercial trip, but not necessarily when towing recreationally, if using WD. I consider many tow ratings to have little technical basis. Not all. I wouldn’t want to exceed the tow rating of a recent North American pickup, or even necessarily tow at the capacity rating, as I think the manufacturers are already pushing it. I don’t consider some receiver ratings to be very accurate, but wouldn’t exceed one without investigation and some judgement. That doesn’t have to include FEA or fatigue considerations to me, it could simply be an evaluation of the design and comparison to other offerings, more a state of the art evaluation, best practices.

For all of the ratings, I don’t set out to arbitrarily reclaim some of the built in safety factor, because it isn’t mine to use, the designer put it in for a reason. I think it is risky to just say that there is a safety factor so “she’ll be right“, as my Australian friends like to say.

I think there can be too much focus on the numbers. I don’t think ratings by themselves make a combination safe, and there is a tendency for some to assume their safety based on being under ratings. What the article at the beginning of this thread said, when discussing 1/2 and 3/4 ton pickup alternatives, was that in many cases the 1/2 ton could be part of a safer combination, due to better handling, better match, TV suspension design, etc, considering the ability of the vehicle to handle axle loads, and despite the GVWR. That the GVWR could be arbitrary when considering towing with WD. Not that it always was. But IMO all the discussion has been more about the words arbitrary and meaningless, not so much about the meat of the proposition, which was to not just focus on the rating, especially for when other items traded off in the pursuit of a higher rating compromise the result instead of improving it.