Airstream 25RB with 1300 Pounds of Payload on TV?

[KK4YZ]

Originally Posted by smithcreek

You guys might be talking about different things? The weight on the hitch vs. the weight added to the TV. I've seen people think that since a WD hitch takes overall weight off the TV axles it also takes weight off the hitch receiver. But the hitch receiver still gets the full tongue weight. It's only how the weight is distributed between the TV and trailer axles that changes.

For example, I've seen people say "my hitch is rated to 800 lbs. max tongue weight, and my trailer's tongue weight is 1000 lbs., but that's ok because when I use the WD hitch only 700 lbs. is added to the TV. so that's below my max tongue weight", which is incorrect.

Actually what is in question is how much of the tongue weight contributes to the tv load. My point is that, because some of the tongue weight is transferred back to the trailer axles by the WD hitch, not all of the static tongue weight goes against the TV load limits.

[gypsydad]

Originally Posted by rmkrum

It’s not so much the missing rivets but where they are. However, improper loading is usually fatal in the airplane business. I have witnessed, in person, a very bad crash due to a load shift. Weight distribution can also bite you with a trailer. The incident caused 15 fatalities (all aboard) and loss of aircraft at sea. No fun. This is the stuff of nightmares

Heck, leaving a flashlight in the linkage area of the aileron can also cause an incident...seen a launch of one of our birds go immediately into a spin, before it broke free...pilot circled and landed safely...but I digress....

[gypsydad]

Originally Posted by jcl

The US and Canada have harmonized regulations, so that vehicles built for one jurisdiction can be sold in either. That said, the BMW I referenced (and the one listed above by Bono) were both built in the US.

SAE J2807 isn't a legal requirement. It is not legislated. It is a testing procedure designed by a professional association, not the government.

If you want to see the legal requirements for weights, check out the Federal Motor Vehicle Safety Standards, that is where they are defined, for the US. When you do that, check out what they say about tow ratings.

I never referenced all BMWs on a lot having the same number. I referenced all the ones of a specific model/platform built that year having the same number, regardless of their installed optional equipment (let's leave out dealer installed items for a while, as that just confuses the discussion) It didn't matter whether these vehicles were equipped with a larger engine, a smaller engine, or any combination of options. This breaks the paradigm that you described. It is an alternate approach that manufacturers can take. They can make the GVWR the variable number, instead of the payload, as long as they are prepared to sell the vehicle with a higher GVWR on one vehicle vs another. It makes listing payload easier for them. It also makes a mockery of the claim that the GVWR is somehow specifically tied to safety. It isn't. Your experience with these calculations on a specific pickup is not applicable to all registered vehicles. That was the point.

Of course these SUVs were designed to tow a heavy trailer, I pointed out why above. Tow ratings up to 3500 kg substantiate that. Note that all model variations had the same tow rating, they didn't derate some and uprate others based on optional equipment. That is a North American pickup approach, and is probably indicative of the pickup manufacturer pushing the published ratings much closer to the design spec, so that they effectively have to derate some variants because they don't have a large enough transmission cooler or radiator, or the appropriate axle ratio, etc. The SUVs I described come equipped to tow the maximum ratings, for all variants. Doesn't that tell you something about that manufacturer's approach vs the North American pickup truck manufacturer?

Currently, my understanding is that all the major manufacturers of trucks conform to the J2807 standard for max limits. Here is an overview of how it is applied: “Performance requirements for determining tow-vehicle gross combination weight rating and trailer weight rating,” : the standard, measures a vehicle’s ability to safely tow by measuring braking distances, acceleration times, passing ability, grade-climbing ability, and physical load-carrying capability.

Lets consider your not paying attention to the max payload sticker; or you just don't care to follow the Mfg max payload sticker of your vehicle, and your overweight/overloaded. What happens should you have an accident because your brakes fail or suspension gives out. Will the Mfg. cover if your still under warranty? Will your insurance adjuster check if your over weight? If you truly believe the max payload sticker is not accurate for said vehicle, what do you think the insurance adjuster would look at in an accident? As I said earlier, you can follow your beliefs, but that doesn't make it correct. Why would you not pay attention to the sticker anyway??

From another site with same discussion:
Best Answer: Overheat your engine, transmission, transfer case or differential. Over stress same components, causing excessive wear and possibly premature failure. Brake fade/failure due to excess weight, possibly causing accident. You could also be ticketed for exceeding the GVWR of the towing vehicle.

[thewarden]

Originally Posted by KK4YZ

Actually this is not correct. With WD used, there’s a force-couple applied at the hitch. The end result is taking some load off the rear axle and transferring some of the load to the tv front axle and some to the trailer axles(s). Not all of your tongue weight contributes to the load on the tv.
Think of the “couple” as a rotational force (bending moment) in the direction of the tv front axle.

How much is transferred depends on the WD adjustment. It’s not 50% (or shouldn’t be). It’s possible to “overhitch” the setup (too much load taken off tv rear axle), resulting in an unstable setup.

I am very familiar with how the WD works, and you are correct, not all the tongue weight contributes to the load on the TV as some is moved back to the trailer. However, that is significantly less that what remains on the TV after moving some of the rear axle weight to the front axle. Back to my point, no mater how much WD is applied, you are not taking anything off of the TOW BALL.

[thewarden]

Originally Posted by Bill M.

The WD bars attach to the hitch head. The bars reduce the weight transferred to the TV via the hitch. So the attachment of the hitch to the TV sees less force from weight. Just the ball and the hitch head see the full tongue weight.

This is exactly correct.

[out of sight]

But you are putting quite an upward bending moment on the hitch receiver with a weight distribution hitch. When you lift up the wd bars with, say, 400 lbs each of force at 2.5 feet from the receiver, you will put 2000 ft-lbs on the receiver. Compare that to a 1000 pound load at 1/2 foot from the receiver when towing on the ball. That's only 500 ft-lbs. This is why some manufacturers, particularly those of unibody construction, do not allow weight distribution hitches. They could damage the unibody.

[gypsydad]

Here are a couple more articles on towing and payload...this site is pretty good read.

https://vehq.com/truck-payload/

https://vehq.com/towing-capacity-trailer-weight/

Also, 1/2T F150 and towing...

https://vehq.com/size-travel-trailer-f-150-pull/

[jcl]

Originally Posted by gypsydad

Currently, my understanding is that all the major manufacturers of trucks conform to the J2807 standard for max limits. Here is an overview of how it is applied: “Performance requirements for determining tow-vehicle gross combination weight rating and trailer weight rating,” : the standard, measures a vehicle’s ability to safely tow by measuring braking distances, acceleration times, passing ability, grade-climbing ability, and physical load-carrying capability.

Lets consider your not paying attention to the max payload sticker; or you just don't care to follow the Mfg max payload sticker of your vehicle, and your overweight/overloaded. …..

There is some crossover between payload and tow ratings going on here. But the following may help with the tow rating part, since J2807 has been quoted.

Again, SAE is an association of professionals. I was a member for years, and I know the SAE. The SAE is not a legal entity in that it writes laws. Their standards are not regulations, which was your claim. J2807 is a testing standard. It defines how to arrive at a nominal rating, it doesn't define what is safe. It is like the SAE horsepower standard. It says what one hp is, and how to test how many hp an engine has, but it doesn't say how much you should have.

Furthermore, the SAE standards aren't always aligned with safety regulations. One example would be that a manufacturer could claim compliance with the SAE J2807 towing standard, and people might then feel comfortable with their tow vehicle braking capability. But the SAE towing standard calls for brake tests from only 20 mph. That's it. If the SAE test standard was a safety standard, it would logically require brake tests at commonly travelled speeds. But it doesn't.

Furthermore, the actual safety regulators don't agree with SAE on this notion of weights and safety impact. In the US, the safety regulator is the FMCSA, the Federal motor carrier safety administration. They proposed a new rule to calculate GCWR a while back. They felt it was confusing that some manufacturers published a GCWR, and others didn't. And the GCWR wasn't necessarily on the door jamb label. So, they proposed to simplify the definition of GCWR. They proposed that the GCWR can be either the number the tow vehicle manufacturer states, or it can be the sum of the GVWRs of the tow vehicle and the trailer. The official GCWR is also stated to be the higher of the two values. In other words, if I drive a 6000 lb GVWR vehicle, and tow a 7600 GVWR trailer, my legal GVWR is 13,600 lbs, regardless of whether the manufacturer of my tow vehicle publishes a lower GCWR.

This can be mind-blowing for those who believe that the GCWR figures are maximums determined by the two vehicle manufacturer. It demolishes the concept that the GCWR is strictly defined as a function of tow vehicle capability. It also demolishes the idea that a judge will use a tow vehicle manufacturer's recommendations as proof of overloading, when the Federal regulator specifically publishes contrary advice.

When the ruling was made five years ago, there was a period of hearings and consultation. And, expectedly, the SAE trailer committee wrote in to say they did not agree.

“SAE and the SAE Tow Vehicle Trailer Rating Committee (SAE TVTRC) do not believe [the proposed definition] is an appropriate methodology for determining GCWR. . . . GCWR covers performance requirements for systems including (but not limited to) power unit engine, transmission, drive axle, powertrain cooling, steering, suspension, brake and structural systems, and as such, can only properly be determined by the power unit manufacturer. Summing the GVW or GVWR values of power unit and towed unit(s) may result in an actual Gross Combination Weight condition but it will not necessarily produce a Gross Combination Weight RATING, as the resultant may not even be close to the value tested and validated by the power unit manufacturer. . '

Their comments were considered, and then discounted.

"FMCSA does not share SAE's apparent belief that vehicle operators would load their combinations to a GCWR allowed by this rule that might exceed the GCWR established by the manufacturer of the towing vehicle. The Truck & Engine Manufacturers Association also expressed no concern over that possibility...."

So, SAE developed a standard for standardizing tow ratings. The actual regulator, the one in charge of road safety, and who has the word Safety in their name, said that is fine, but we don't consider it to have impacts on safety, and it doesn't have legal standing.

Read all about it here: https://www.federalregister.gov/docu...ing-definition

When ever someone posts FUD (Fear and Doubt) it should be examined to see if it is valid. And while web blog posts about "what is a tow rating and what is a GCWR" can be interesting, they should not be taken as true just because they are on the internet. That should be self-evident. Actual regulations are more trusted sources IMO.

As to the last part of your post, I make sure I do not exceed axle weight ratings (and my tire ratings are well above my axle ratings, so I don't check them regularly) That is what describes being overloaded. Legally. Unless I am a commercial carrier, and subject to additional regulations based on GCWR and often related to classes of driver's licenses, driver's log books, etc. I also understand the impact on my vehicle of towing heavier loads, and understand the difference between my responsibilities as an operator, and the tow vehicle manufacturer's obligations to warrant defects related to parts and materials. They don't warrant suitability for purpose, or operation. Your state level laws may differ.

[smithcreek]

Originally Posted by Bill M.

The WD bars attach to the hitch head. The bars reduce the weight transferred to the TV via the hitch. So the attachment of the hitch to the TV sees less force from weight. Just the ball and the hitch head see the full tongue weight.

I understand the basic discussion is about weight distribution among the axles, but I've seen people confusing distribution and thinking a WD system actually made tongue weight lighter. Not saying you, but seen it many times. Literally seen people thinking they could use weight distribution to tow a trailer with 1000 lbs. tongue weight on a hitch with 750 lbs. max because WD would make it light enough.

The ball itself will see a lot more than full tongue weight with WD. Drop the coupler on the ball and the ball supports the full tongue weight. Crank the WD bars and you increase the weight measure at the ball. But if you measure the weight at the shank/receiver before and after the WD chains were tightened it would be the same. The receiver/hitch is what sees the full tongue weight, then it's responsible for distributing that load between the axles.

[jcl]

Originally Posted by out of sight

But you are putting quite an upward bending moment on the hitch receiver with a weight distribution hitch. When you lift up the wd bars with, say, 400 lbs each of force at 2.5 feet from the receiver, you will put 2000 ft-lbs on the receiver. Compare that to a 1000 pound load at 1/2 foot from the receiver when towing on the ball. That's only 500 ft-lbs. This is why some manufacturers, particularly those of unibody construction, do not allow weight distribution hitches. They could damage the unibody.

If a manufacturer specifically advises against using WD equipment with their standard hitch, it is worth having a towing professional check the hitch and modify it if necessary, or buying an aftermarket hitch that is rated for the expected loads and use.

If a manufacturer is silent on the subject of WD hitches, especially with unibody vehicles, it probably means that they have no concerns.

If a manufacturer is silent on the subject of WD hitches, it may mean that they are a European manufacturer, with engineering teams that have simply not looked at WD hitch use cases, because such hitches are not commonly used where they design the vehicle and live.

[jcl]

Originally Posted by smithcreek

I understand the basic discussion is about weight distribution among the axles, but I've seen people confusing distribution and thinking a WD system actually made tongue weight lighter. Not saying you, but seen it many times. Literally seen people thinking they could use weight distribution to tow a trailer with 1000 lbs. tongue weight on a hitch with 750 lbs. max because WD would make it light enough.

The ball itself will see a lot more than full tongue weight with WD. Drop the coupler on the ball and the ball supports the full tongue weight. Crank the WD bars and you increase the weight measure at the ball. But if you measure the weight at the shank/receiver before and after the WD chains were tightened it would be the same. The receiver/hitch is what sees the full tongue weight, then it's responsible for distributing that load between the axles.

Agree with your comments, but would add two more.

Tongue weight is confused with effective tongue weight, as a shorthand form. For example, if I have 1000 lbs of tongue weight and use WD, the effective tongue weight in terms of tow vehicle payload is likely to be less than 1000 lbs.

Also, tongue weight is confused with rear axle weight. If I have 1000 lbs of tongue weight (leave out WD for a moment) many posters consider that they have 1000 lbs on the rear axle of their tow vehicle when calculating loads. That is only true if the hitch connection is positioned over the rear axle. They are more likely to have something like 1200 lbs on their rear axle, and 200 lbs less on their front axle (just as examples).

[gypsydad]

Originally Posted by jcl

There is some crossover between payload and tow ratings going on here. But the following may help with the tow rating part, since J2807 has been quoted.

Again, SAE is an association of professionals. I was a member for years, and I know the SAE. The SAE is not a legal entity in that it writes laws. Their standards are not regulations, which was your claim. J2807 is a testing standard. It defines how to arrive at a nominal rating, it doesn't define what is safe. It is like the SAE horsepower standard. It says what one hp is, and how to test how many hp an engine has, but it doesn't say how much you should have.

Furthermore, the SAE standards aren't always aligned with safety regulations. One example would be that a manufacturer could claim compliance with the SAE J2807 towing standard, and people might then feel comfortable with their tow vehicle braking capability. But the SAE towing standard calls for brake tests from only 20 mph. That's it. If the SAE test standard was a safety standard, it would logically require brake tests at commonly travelled speeds. But it doesn't.

Furthermore, the actual safety regulators don't agree with SAE on this notion of weights and safety impact. In the US, the safety regulator is the FMCSA, the Federal motor carrier safety administration. They proposed a new rule to calculate GCWR a while back. They felt it was confusing that some manufacturers published a GCWR, and others didn't. And the GCWR wasn't necessarily on the door jamb label. So, they proposed to simplify the definition of GCWR. They proposed that the GCWR can be either the number the tow vehicle manufacturer states, or it can be the sum of the GVWRs of the tow vehicle and the trailer. The official GCWR is also stated to be the higher of the two values. In other words, if I drive a 6000 lb GVWR vehicle, and tow a 7600 GVWR trailer, my legal GVWR is 13,600 lbs, regardless of whether the manufacturer of my tow vehicle publishes a lower GCWR.

This can be mind-blowing for those who believe that the GCWR figures are maximums determined by the two vehicle manufacturer. It demolishes the concept that the GCWR is strictly defined as a function of tow vehicle capability. It also demolishes the idea that a judge will use a tow vehicle manufacturer's recommendations as proof of overloading, when the Federal regulator specifically publishes contrary advice.

When the ruling was made five years ago, there was a period of hearings and consultation. And, expectedly, the SAE trailer committee wrote in to say they did not agree.



Their comments were considered, and then discounted.



So, SAE developed a standard for standardizing tow ratings. The actual regulator, the one in charge of road safety, and who has the word Safety in their name, said that is fine, but we don't consider it to have impacts on safety, and it doesn't have legal standing.

Read all about it here: https://www.federalregister.gov/docu...ing-definition

When ever someone posts FUD (Fear and Doubt) it should be examined to see if it is valid. And while web blog posts about "what is a tow rating and what is a GCWR" can be interesting, they should not be taken as true just because they are on the internet. That should be self-evident. Actual regulations are more trusted sources IMO.

As to the last part of your post, I make sure I do not exceed axle weight ratings (and my tire ratings are well above my axle ratings, so I don't check them regularly) That is what describes being overloaded. Legally. Unless I am a commercial carrier, and subject to additional regulations based on GCWR and often related to classes of driver's licenses, driver's log books, etc. I also understand the impact on my vehicle of towing heavier loads, and understand the difference between my responsibilities as an operator, and the tow vehicle manufacturer's obligations to warrant defects related to parts and materials. They don't warrant suitability for purpose, or operation. Your state level laws may differ.

Very interesting read from 2014, I believe? (I also was a membership chairman for ASME for few years, early on in my career where I also worked with Ford and GM engineers on new development technologies; that's one reason I moved into technical sales; too many specs to understand!)…

Couple points I pulled from this:

FMCSA amends the Federal Motor Carrier Safety Regulations (FMCSRs) by revising the definition of “gross combination weight rating” (or GCWR) to clarify the applicability of the Agency's safety regulations for single-unit trucks (vehicles other than truck tractors) when they are towing trailers, and the GCWR information is not included on the vehicle manufacturer's certification label.

and...
When these combined GVWRs exceed the weight thresholds for the safety regulations (10,001 pounds) or the CDL regulations (26,001 pounds), the operators will be held accountable. The new definition also allows enforcement officers to combine actual weights with GVWRs and to treat the heaviest combined value as the GCWR.

As you pointed out, you don't overload; I don't overload either. I try to stay within the Mfg. posted specs...
think that about covers it; for us anyway...

[jcl]

Originally Posted by gypsydad

Very interesting read from 2014, I believe? (I also was a membership chairman for ASME for few years, early on in my career where I also worked with Ford and GM engineers on new development technologies; that's one reason I moved into technical sales; too many specs to understand!)…

Couple points I pulled from this:

FMCSA amends the Federal Motor Carrier Safety Regulations (FMCSRs) by revising the definition of “gross combination weight rating” (or GCWR) to clarify the applicability of the Agency's safety regulations for single-unit trucks (vehicles other than truck tractors) when they are towing trailers, and the GCWR information is not included on the vehicle manufacturer's certification label.

and...
When these combined GVWRs exceed the weight thresholds for the safety regulations (10,001 pounds) or the CDL regulations (26,001 pounds), the operators will be held accountable. The new definition also allows enforcement officers to combine actual weights with GVWRs and to treat the heaviest combined value as the GCWR.

Yes, commercial operators can be held liable. But not non commercial carriers, as most are here. The GCVWR is designed to be applicable to commercial carriers, not to individuals. The term GCVWR is misused for non commercial carriers applications, and often quoted in posts about towing travel trailers, but it simply doesn't have a legal basis. Not many seem to realize that. I am not saying it is worthless, but it certainly isn't the basis of any legal responsibility.

[thewarden]

It may very well be that it doesn't apply to non commercial but I recall a number of years back the B.C. highway guys were pulling over almost every RV coming into the Province at the scales on the Trans Canada just inside the B.C. border. They were checking door stickers and sending us all over the scale. A number of rigs were turned around right there and sent back to Alberta. All overloaded. I don't believe anyone got fined but I understand they were told to lighten up before returning. They were just trying to keep the mountain roads safe for all travellers from the possible dangerous side effects of overloaded RVs.

[jcl]

Originally Posted by thewarden

It may very well be that it doesn't apply to non commercial but I recall a number of years back the B.C. highway guys were pulling over almost every RV coming into the Province at the scales on the Trans Canada just inside the B.C. border. They were checking door stickers and sending us all over the scale. A number of rigs were turned around right there and sent back to Alberta. All overloaded. I don't believe anyone got fined but I understand they were told to lighten up before returning. They were just trying to keep the mountain roads safe for all travellers from the possible dangerous side effects of overloaded RVs.

The post above yours is about the GCWR, not the GVWR. The definition of GVWR did not change with the ruling described above.

GVWR enforcement is generally applied to commercial carriers, but not uniformly, and BC is one of the exceptions. It has its roots in our very steep terrain, and a long history of tougher regulations for over the road vehicles. It isn't because we don't like Albertans, current disputes notwithstanding.

BC has a long history of logging, has coastal forests with very large trees, and we also had several logging truck manufacturers that designed and built for BC conditions, and exported globally. (Pacific, Hayes) That resulted in BC writing truck braking laws that exceeded national standards. Manufacturers typically brought their trucks to BC for testing, on the basis that BC had the toughest standards.

The current manifestation of this is that the Commercial Vehicle Safety and Enforcement (CVSE) team watch for overloading (weight carried, not weight towed). There was a change to the regulations for vehicles under 5500 kg GVWR, focused on RVs.

They use visual cues to decide who to pull over, like headlights pointed up and obvious cases of overloading/unsafe loads. They then weigh the vehicle, and can issue tickets, also to private operators, and can also order the vehicle off the road. If they are set up on the BC/Alberta border it is easiest just to turn them around. Note that they do not focus on GCWR or towing limits; that is not part of their safety enforcement program.

I was at a CVSE scale at the foot of the Coquihalla in Hope in December and the truck I was driving was slightly over on the front axle, about 100 kg, and under the total GVWR. I was towing, without WD (small trailer) and there were no concerns there, it was the truck GVWR that required me to stop and get weighed. They didn't get a good reading, asked me to come around again and reweigh, and then weren't worried at all, and advised me to just be aware of it next time I loaded the truck. They were very professional.

The BC CVSE guidance is here: https://www.cvse.ca/references_publi...82003)GVWR.pdf

[jcl]

Originally Posted by gypsydad

FMCSA amends the Federal Motor Carrier Safety Regulations (FMCSRs) by revising the definition of “gross combination weight rating” (or GCWR) to clarify the applicability of the Agency's safety regulations for single-unit trucks (vehicles other than truck tractors) when they are towing trailers, and the GCWR information is not included on the vehicle manufacturer's certification label.

A clarification on this. Even when the GCWR is included on the tow vehicle manufacturer's label, it is not the governing figure for the safety regulations. The regulation uses the larger of the numbers obtained by the two methods.

"The Agency agrees that even if the manufacturer's GCWR were displayed on the NHTSA label, the proposed definition would use the sum of the GVWRs as the GCWR if that sum exceeded the value specified by the manufacturer."

[thewarden]

Originally Posted by jcl

The post above yours is about the GCWR, not the GVWR. The definition of GVWR did not change with the ruling described above.

GVWR enforcement is generally applied to commercial carriers, but not uniformly, and BC is one of the exceptions. It has its roots in our very steep terrain, and a long history of tougher regulations for over the road vehicles. It isn't because we don't like Albertans, current disputes notwithstanding.

BC has a long history of logging, has coastal forests with very large trees, and we also had several logging truck manufacturers that designed and built for BC conditions, and exported globally. (Pacific, Hayes) That resulted in BC writing truck braking laws that exceeded national standards. Manufacturers typically brought their trucks to BC for testing, on the basis that BC had the toughest standards.

The current manifestation of this is that the Commercial Vehicle Safety and Enforcement (CVSE) team watch for overloading (weight carried, not weight towed). There was a change to the regulations for vehicles under 5500 kg GVWR, focused on RVs.

They use visual cues to decide who to pull over, like headlights pointed up and obvious cases of overloading/unsafe loads. They then weigh the vehicle, and can issue tickets, also to private operators, and can also order the vehicle off the road. If they are set up on the BC/Alberta border it is easiest just to turn them around. Note that they do not focus on GCWR or towing limits; that is not part of their safety enforcement program.

I was at a CVSE scale at the foot of the Coquihalla in Hope in December and the truck I was driving was slightly over on the front axle, about 100 kg, and under the total GVWR. I was towing, without WD (small trailer) and there were no concerns there, it was the truck GVWR that required me to stop and get weighed. They didn't get a good reading, asked me to come around again and reweigh, and then weren't worried at all, and advised me to just be aware of it next time I loaded the truck. They were very professional.

The BC CVSE guidance is here: https://www.cvse.ca/references_publi...82003)GVWR.pdf

Yes, I understand the difference between GVWR and GCWR. The point is, if you exceed your GCWR enough you will also exceed your GVWR.

Please don't misunderstand. I wholeheartedly support what they are doing in B.C. with RVs. Driving B.C. highways are like nowhere else because of the mountainous terrain, which can make driving even a properly loaded RV a challenge.

I have RVd throughout B.C. frequently over the past 30 years and I can't count the number of times some obviously overloaded RV has thundered by me 2/3 the way down a decent grade, every brake on the TV and trailer literally smoking well before the bottom of the hill and then have me pass him up the next grade.

It has been said several times on this and other threads, you can tow with darn near anything. But how safely. When you insist that vehicle capacity stickers are only suggestions or guidelines and you know know better than the engineers who calculated these capacities, you are just foolish at best and dangerous at worst.

[jcl]

Originally Posted by thewarden

It has been said several times on this and other threads, you can tow with darn near anything. But how safely. When you insist that vehicle capacity stickers are only suggestions or guidelines and you know know better than the engineers who calculated these capacities, you are just foolish at best and dangerous at worst.

I have great respect for vehicle capacity ratings (tires, axles, GVWR, all defined by regulatory agencies). I just don't consider most tow ratings to be engineering capacity limits. They may be in some cases, certainly, and I am thinking here of light duty pickup trucks where over the past few years manufacturers raced to out do each other in their advertising claims for high tow ratings. But other times the tow ratings are simply arbitrary, particularly with the SUVs that I like to tow with.

The posts above describe the legal basis for the GCWR. If I choose to tow a heavier trailer than the recommended tow rating of my vehicle manufacturer, the US Federal Safety agency that defines GCWR says that my new GCWR is the sum of my tow vehicle GVWR plus my trailer GVWR. So there is the legal liability issue addressed, at least in terms of exceeding the manufacturer's tow rating. Legally, the GCWR isn't exceeded.

Now, if I want to tow a heavier trailer I need to address the limitations of my hitch receiver, respect my tow vehicle tire/axle/GVW ratings, and drive appropriately.

My first BMW SUV had a 7700 lb tow rating by the designers, but was sold with only a 6000 lb rated hitch in North America, unless one wanted to install an aftermarket hitch. There was no tow rating listed in the owner's manual, or on the door jamb sticker. The only recommendation came in the installation instructions for the hitch receiver. My next BMW SUV weighed the same, was very close to the same size, had more HP, better brakes, approximately the same GVWR, and was supplied with a 3500 lb rated hitch if I wanted to purchase one from the dealer. That left only the aftermarket. Many claim that my second SUV has a 3500 lb tow rating as a vehicle design limitation. That doesn't make any sense. It has a manufacturer's 3500 lb tow rating when equipped with the standard hitch receiver. The real world tow rating (based on engineering design principles) goes beyond the spec of the hitch receiver. I don't know the real upper limit, and don't intend to experiment to find out, but don't feel bound by the 3500 lb tow rating.

The above approach doesn't make me foolish or dangerous in and of itself, IMO. (Speaking as an engineer)

[thewarden]

To clarify, my foolish comment relates to those who choose to exceed cargo capacities and GVW ratings. It was in no way directed at you.

[jcl]

Originally Posted by thewarden

To clarify, my foolish comment relates to those who choose to exceed cargo capacities and GVW ratings. It was in no way directed at you.

Thank you.