Are They Meaningless? Tow Limits, Payload and Axle Load

[CanyonMan]

Originally Posted by BayouBiker

The rational observer would note the hitch location is different and would correctly conclude the formulation is different. Single wheels add 30-50% capacity, dual wheels nearly 100%. The eight wheeled semi-tractors quite a bit more still. The game changer is hitch location. A full explanation would be quite complex and drawn out.

I only wish I were as smart as you.

Canyon.

[Ultraclassic]

Originally Posted by DAVSCH

We've all seen the clip, a bicyclist pulls an Airstream. Bravo. The real problem is the legalities. Get in a accident while towing anything and the police are going to take down data plate numbers. If you're exceeding limits on the plates, you're in a world of hurt. It doesn't matter if you've added everything under the sun to the tow vehicle to beef up it's capacities, the data plate remains the same unless you have the auto manufacturer evaluate your vehicle and issue a new data plate. Personally, I will NOT give the ambulance chasers that avenue to strip me of everything I own while I defend myself from them. Do as you see fit to loose.

But the "plates" would show this

Trailer GVW 7200lbs

1/2T truck Tow capacity 8600lbs

Check it's ok

Done

No tongue weight or payload in the discussion

[Profxd]

Consider this scenario. There are 2 towing combinations. Both are using the exactly the same TV, same driver and TV loading, hitch, FALR, both trailers weigh the same with the same TW. One rig tows great up to 75 mph, sway dampens quickly, trucks passing have little affect on it. The other rig becomes a handful above 60 mph, the least little excitation from a external force sends it weaving back and forth.

The question is as a driver and needing to b eresponsible do you have the knowledge to make rig 2 tow just like the first? All the weights are the same including FALR so what do you do? It’s my belief that nearly everyone on this forum including those that believe they are way smarter then everyone else would fail. The scenario above gets repeated constantly on RV forums, unrealistic generalizations about overall weight useless.

[ROBERT CROSS]

^
I've had no problems setting up my trailers and don't worry about the imaginary ones.


Let us know when you run across that very rare scenario and we'll try to help. 😂

Bob
🇺🇸

The AF Creed....
“If you’re happy with what you’re using…it’s adequate.
If other people are un-happy….it’s not”
RLC

[Shiny16]

Originally Posted by Profxd

Consider this scenario. There are 2 towing combinations. Both are using the exactly the same TV, same driver and TV loading, hitch, FALR, both trailers weigh the same with the same TW. One rig tows great up to 75 mph, sway dampens quickly, trucks passing have little affect on it. The other rig becomes a handful above 60 mph, the least little excitation from a external force sends it weaving back and forth.

The question is as a driver and needing to b eresponsible do you have the knowledge to make rig 2 tow just like the first? All the weights are the same including FALR so what do you do? It’s my belief that nearly everyone on this forum including those that believe they are way smarter then everyone else would fail. The scenario above gets repeated constantly on RV forums, unrealistic generalizations about overall weight useless.

No matter how careful you are when walking down the sidewalk a piano might fall on your head. I suspect that most would agree it still pays to be careful.

[Profxd]

Originally Posted by ROBERT CROSS

^
I've had no problems setting up my trailers and don't worry about the imaginary ones.


Let us know when you run across that very rare scenario and we'll try to help. 😂

Bob
🇺🇸

The AF Creed....
“If you’re happy with what you’re using…it’s adequate.
If other people are un-happy….it’s not”
RLC

Then maybe you should stop giving out advice then to those that do have problems.

[ROBERT CROSS]

Originally Posted by Profxd

Then maybe you should stop giving out advice then to those that do have problems.

Sorry if your ego got bruised....

Good luck in your search.

Again, let us know if we can help.

Bob
🇺🇸

[KK4YZ]

Originally Posted by Shiny16

No matter how careful you are when walking down the sidewalk a piano might fall on your head. I suspect that most would agree it still pays to be careful.

Watching old Laurel and Hardy clips on YouTube again, eh?😂

[BayouBiker]

Profxd, is this a real situation or a hypothetical? One way this might happen would take a confluence of specific configuration conditions along with very poor and akward Airstream trailer loading along with poor tire inflation to get the dramatic difference you describe. Perhaps the trailer was not a travel trailer at all....

[Collyn]

Originally Posted by Profxd

Consider this scenario. There are 2 towing combinations. Both are using the exactly the same TV, same driver and TV loading, hitch, FALR, both trailers weigh the same with the same TW. One rig tows great up to 75 mph, sway dampens quickly, trucks passing have little affect on it. The other rig becomes a handful above 60 mph, the least little excitation from a external force sends it weaving back and forth.

The question is as a driver and needing to b eresponsible do you have the knowledge to make rig 2 tow just like the first? All the weights are the same including FALR so what do you do? It’s my belief that nearly everyone on this forum including those that believe they are way smarter then everyone else would fail. The scenario above gets repeated constantly on RV forums, unrealistic generalizations about overall weight useless.

I do not for a moment believe I am smarter than others on this forum, but having spent much of my working life assisting and writing and publishing professionally in this area, feel I can at least comment.

In the scenario you describe there will be some causal explanation. It is most likely that the tow vehicle has too low rear tyre pressure, but there may be a combination of multiple minor issues. Random-like behaviour can set in but usually at speeds above 60 mph.

My own experience in assisting Australians with such issues is that owners often guess weights (yet present that as data) but mainly have unrealistic expectations about what can be safely towed by their tow vehicle. Further, do not understand the huge forces involved when some five to eight tonnes travel at above about 60 mph. Fortunately, most of Australia has a tow speed limit of about that.

Collyn

[Profxd]

Originally Posted by BayouBiker

Profxd, is this a real situation or a hypothetical? One way this might happen would take a confluence of specific configuration conditions along with very poor and akward Airstream trailer loading along with poor tire inflation to get the dramatic difference you describe. Perhaps the trailer was not a travel trailer at all....

This near exact scenario is reported regularly on RV forums across the web. When someone reports a bad handling combination there’s always someone with the same truck same trailer and hitch combination that tows perfectly fine. It’s a trailer loading issue in most cases which seems to always go ignored. You can have 2 trailers loaded to the same overall weight with the same tongue weight % yet one trailer can still have a 30% + higher yaw inertia. That much increase in yaw inertia would result in a 13-15 mph decrease in critical speed and most likely a pitching (porpoising) problem as well which just makes things worse. The given advice is usually to replace the WDH to brand X, upgrade the TV suspension (shocks, air bags), add more tension to the WDH, or replace the TV to the next higher class.

[JayOhBee]

Can I tow _this_ travel trailer with _that_ tow vehicle? Probably the most asked question on this forum. Certainly the most answered question on this forum. I am adding my voice to the ongoing discussion. I would like to start by recognizing that this is complicated. There are lots of numbers and lots of variables. Weather, driver ability, road conditions and many more. Once all the number crunching is done, you have chosen a setup, and you are on the road the theories don't matter so much any more. When the wind picks up and blows your trailer around or something breaks as you are heading down a steep grade, it is no longer theory it's reality. It matters. That said, I suggest that you start with the numbers. IMHO, they provide a good framework for determining risk.

Let's say that you exceed one of these limits. Is it still safe to tow? Will your rear axle buckle under the load? Will your TT push your TV off the road when a semi passes you? It's hard to say in any specific case. The limits are determined based on a set of assumptions, statistics, engineering, and live tests. However, they are not protection against failures. They provide guidance that tell us that if you stay within these limits, most problems will occur at an acceptably low rate. As the limits are exceeded, the rate of incident increases. Being 250 pounds over weight on any axle does not mean you will definitely have a problem. It just increases the probability. Exceeding multiple limits generally increases the rate of incidents as the product of the failure rates, so 5 times 4 rather than 5 plus 4. If you are overweight by 500 pounds on your drive axle and the tires on the drive axle are under pressure by 15 psi, the combination is far more likely to cause a problem than either one of those individually. Also note that a problem does not need to be an accident. It could be excessive wear or premature failure of one or more components. Of course, if undetected this could lead to something more serious.

Generally the objective is to set up a TV/TT combination that meets your needs/desires and provides an acceptable margin of safety. Everyone has their own opinion on how wide that margin of safety needs to be. Some argue that the vehicle ratings are meaningless, others that they are absolute. I feel that reality is somewhere in the middle. From what I have seen it is pretty easy to find someone who has successfully towed with almost any combination. I have also seen that it is pretty easy to find someone who started out towing with a specific combination but eventually upgraded and would never go back or recommend the original to anyone else. People who have _not_ successfully towed, ie. had critical failures and/or serious accidents on the road are much harder to come by, I assume because people tend not to post negatives about themselves.

So do the limits matter? It is generally up to the individual. Personal vehicles are not weighed like commercial vehicles are, and although there has been much discussion about being weighed after an accident, I'm not sure how that would work. I guess it could happen. I do know that when I had a blowout on my Airstream that AAA wanted to know how much the trailer weighed and what the GVWR was. They got the GVWR from the plate of the AS and I showed them a CAT scale ticket for the actual weight. I didn't have to, but I knew I was good. I'm conservative so I stick to the numbers. I purchased a TV that I knew would exceed the requirements for towing my TT. Not everyone can or will do that. I'm OK with that. It is their personal choice. Yes, it could endanger others but this is the world we live in.

[Collyn]

Originally Posted by JayOhBee

Can I tow _this_ travel trailer with _that_ tow vehicle? Probably the most asked question on this forum. Certainly the most answered question on this forum. I am adding my voice to the ongoing discussion. I would like to start by recognizing that this is complicated. There are lots of numbers and lots of variables. Weather, driver ability, road conditions and many more. Once all the number crunching is done, you have chosen a setup, and you are on the road the theories don't matter so much any more. When the wind picks up and blows your trailer around or something breaks as you are heading down a steep grade, it is no longer theory it's reality. It matters. That said, I suggest that you start with the numbers. IMHO, they provide a good framework for determining risk.

Let's say that you exceed one of these limits. Is it still safe to tow? Will your rear axle buckle under the load? Will your TT push your TV off the road when a semi passes you? It's hard to say in any specific case. The limits are determined based on a set of assumptions, statistics, engineering, and live tests. However, they are not protection against failures. They provide guidance that tell us that if you stay within these limits, most problems will occur at an acceptably low rate. As the limits are exceeded, the rate of incident increases. Being 250 pounds over weight on any axle does not mean you will definitely have a problem. It just increases the probability. Exceeding multiple limits generally increases the rate of incidents as the product of the failure rates, so 5 times 4 rather than 5 plus 4. If you are overweight by 500 pounds on your drive axle and the tires on the drive axle are under pressure by 15 psi, the combination is far more likely to cause a problem than either one of those individually. Also note that a problem does not need to be an accident. It could be excessive wear or premature failure of one or more components. Of course, if undetected this could lead to something more serious.

Generally the objective is to set up a TV/TT combination that meets your needs/desires and provides an acceptable margin of safety. Everyone has their own opinion on how wide that margin of safety needs to be. Some argue that the vehicle ratings are meaningless, others that they are absolute. I feel that reality is somewhere in the middle. From what I have seen it is pretty easy to find someone who has successfully towed with almost any combination. I have also seen that it is pretty easy to find someone who started out towing with a specific combination but eventually upgraded and would never go back or recommend the original to anyone else. People who have _not_ successfully towed, ie. had critical failures and/or serious accidents on the road are much harder to come by, I assume because people tend not to post negatives about themselves.

So do the limits matter? It is generally up to the individual. Personal vehicles are not weighed like commercial vehicles are, and although there has been much discussion about being weighed after an accident, I'm not sure how that would work. I guess it could happen. I do know that when I had a blowout on my Airstream that AAA wanted to know how much the trailer weighed and what the GVWR was. They got the GVWR from the plate of the AS and I showed them a CAT scale ticket for the actual weight. I didn't have to, but I knew I was good. I'm conservative so I stick to the numbers. I purchased a TV that I knew would exceed the requirements for towing my TT. Not everyone can or will do that. I'm OK with that. It is their personal choice. Yes, it could endanger others but this is the world we live in.

I agree with the above except only that a typical owner has no safe way of assessing his or her rig's margin of safety. I have (elsewhere) set out a free downloadable multiple question format that enables an owner to realistically assess this - but I fear that forum rules preclude my indicating where.

Collyn

[Shiny16]

Originally Posted by Collyn

I do not for a moment believe I am smarter than others on this forum, but having spent much of my working life assisting and writing and publishing professionally in this area, feel I can at least comment.

In the scenario you describe there will be some causal explanation. It is most likely that the tow vehicle has too low rear tyre pressure, but there may be a combination of multiple minor issues. Random-like behaviour can set in but usually at speeds above 60 mph.

My own experience in assisting Australians with such issues is that owners often guess weights (yet present that as data) but mainly have unrealistic expectations about what can be safely towed by their tow vehicle. Further, do not understand the huge forces involved when some five to eight tonnes travel at above about 60 mph. Fortunately, most of Australia has a tow speed limit of about that.

Collyn

Just curious? Does the fact that your towing everything upside have an effect on stability?

[mkcurtiss]

Well you know there is a skunk in the woodpile, when Ford states that an F-150 can safely tow 13,500 lbs.....Its just an example.

I often use one of my own vehicles to illustrate the foolishness associated with "tow ratings"......

I have one of those Jeep Cherokee's from back in the day.....its a 1992...terrific vehicle and great fun to own.....most useful vehicle I have ever had.....however....the tow rating on that Jeep is 5000lbs.....Now it has the venerable 4.0 high output straight 6, a wicked strong transmission, and 3:55 rear end....but the thing weighs about 3100 lbs.....
My Airstream weighs about 5000 lbs.....Now I use the Jeep to move the Airstream around my property, albeit in low range 4wd, but it would take an absolutely idiotic buffoon to think it would be safe to tow that Airstream with that Jeep, even though you would be within the "tow capacity"......
The moral of the story is, common sense is the most important element in establishing the suitability of a proper tow vehicle for any trailer or load.

[jaybauman]

Originally Posted by mkcurtiss

The moral of the story is, common sense is the most important element in establishing the suitability of a proper tow vehicle for any trailer or load.

The only problem with this statement is that common sense ain't so common.

[ROBERT CROSS]

Originally Posted by Shiny16

Just curious? Does the fact that your towing everything upside(down) have an effect on stability?

Fixed it, you're welcome.

Bob
🇺🇸

[mpsgolf]

Originally Posted by Shiny16

Just curious? Does the fact that your towing everything upside have an effect on stability?

I’ve heard the tires spin the opposite direction down under.

[Shiny16]

Originally Posted by ROBERT CROSS

Fixed it, you're welcome.

Bob
🇺🇸

Opps! Thanks

[Shiny16]

Originally Posted by mpsgolf

I’ve heard the tires spin the opposite direction down under.

..don’t get me started about the toilets.