Help me understand towing weight

[rostam]

FAWR + RAWR > GVWR

At least in all the vehicles I have seen so far


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[jcl]

Originally Posted by switz

When DOT does a stop, they do not care about the door sticker payload, they care about the axle ratings and do the tire ratings equal or exceed the axle ratings. If the scale weight on the axles is lower than their rating, then the vehicle is not overloaded.

The above is independent of the gross combined towing weight with is the total weight of tow vehicle and trailer when attached.

Depends on who stops you, ie which jurisdiction, but I would agree they don't care about payload. And they don't care about tow rating. They do care about tires, axles, as you note, and GVWR, which you don't mention.

[Rocinante]

I keep on reading...please do check my math, as it's been questionable before.

Ram trucks website says tongue weight is "The downward force exerted on the hitch ball by the trailer coupler. In most cases, it should fall between 10 to 25 percent of Gross Trailer Weight." It then further says, "Trailer tongue weight must be accounted for in total payload."

The confusion comes in part from a related statement about Gross Vehicle Weight where it says, "Gross Vehicle Weight (GVW) is the total weight of a fully loaded vehicle, including passengers and payload – but excluding all towing."

Citation: Ram Trucks - Towing Capacity Chart

I guess that exclusion applies to the axle weight of the trailer. So, the trailer's axle weight would be evaluated vs. the TV's remaining towing capacity, not its payload capacity. That's the weight I pull behind the TV vs the weight the TV actually carries on its own two axles.

However, any weight the trailer applies to the TV via the hitch counts against the TV's GVWR...which is considerably less than I had previously believed due to my misinterpretation (e.g. in my truck's case Front GAWR + Rear GAWR is 1K pounds greater than GVWR).

We're well below GAWR for each of the two axles. Unfortunately, I'm now realizing our TV is currently a bit over GVWR when it is hauling the TT.

So, I could move as much as possible out of the truck and into the trailer and move the heavier items into the back of the trailer while making sure we keep 10-12% of the trailer's GVW on the tongue. (I doubt it would be a challenge to keep 10-12% on the tongue.)

Of course, I'm now finding docs that confirm the tongue weight is indeed counted twice - once for the weight it adds to the truck as payload, and again for the weight it adds to the trailer for the trailer's GVW, which must then be compared to the trailer's GVWR. This means my trailer is closer to it's GVWR than I had previously believed. It's not over, but it's roughly 1K pounds closer.

Citation: Trailer Loading and Towing Guide (Weighing the Trailer)

I'm pretty disappointed to discover that despite my prior research I seem to have missed the mark, even though I tried hard to get it right.

If I finally understand everything correctly, the real fun begins with tossing every possible bit of extra weight from the TV and TT, and optimally re-arranging the remaining stuff fore and aft of the trailer axles. Maybe next time I'll just go hot-air ballooning instead of buying a trailer.

[jcl]

I'd say the first step is to evaluate what you really need to bring with you. Then, figure out what can go in the trailer instead of the tow vehicle.

I am pretty sure hot air ballooning will not be any easier....being overloaded there has some pretty serious consequences.

[Rocinante]

Spent the morning tossing out anything remotely redundant, moving everything heavy south of the trailer axles and clearing out the truck bed. We also removed everything we can from every cabinet north of the axles. Given we've an FB model, that includes under-bed storage and front compartment storage. Mostly, the only thing we'll store north of the axles is a few clothes for the trip.

We'll weigh again this week to see whether that's made a useful improvement.


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[Rich W]

[QUOTE=RhinoWW;1506889 Second car is an early model Lexus GX460, essentially a 4Runner V8, with similar stated capacity of 5000, and 6500 with WD.[/QUOTE]

The 2004 4Runner V8 has a (2WD) 7,300 and (4WD) 7,000 towing capacity, with a max trailer weight of (2WD) 5,450 and (4WD) 5,710

Maximum Trailer Tongue Weight
(2WD) 730 (4WD) 700

[TouringDan]

Originally Posted by Dchristrn

I'm also looking for some answers. I have a 1/2 ton 2013 tundra 4x2 crewmax 5.7L V8. The posted GVWR is 7000lbs and a 4.300 rear diff. It has the towing package with the trailer brake prewire. I need to know what size AS trailer I will be safe with. We were looking at a 27 ft. Would it be better to go smaller? Any help would be greatly appreciated as I am a general newbie.

I have a 2008 Tundra 5.7L double cab. It is a great TV. The towing specs are pretty close to your Tundra. My GVWR is 6,900 lbs. The payload is 1,475 lbs and the RAWR (rear axle weight rating) is 4,100 lbs. You may be ok with a 27 ft trailer, but smaller is always better (in terms of safety for towing- hey you asked). Buy the one you want is my advice.

Pharm Geek, post #10, has a pretty good way of defining some terms that can be hard to understand.

Here is how I look at it. Payload is important, but you can't measure it. You can only calculate it. What really is important is the TV GVWR and the RAWR. You can easily measure both. The TV GVW, gross vehicle weight, is the weight measured with both sets of TV tires on the scale with the trailer attached ready for camping. This needs to be less than the GVWR. The TV RAW, rear axles weight, is the weight measured with only the TV rear tires on the scale, with the trailer attached ready for camping. This needs to be less than the RAWR. If both the GVW and RAW are fine, you are in good shape.

Dan

[Rocinante]

So, will a 1/2 ton pickup with a GVWR of 7,000 pounds and a towing capacity of 9,000+ pounds tow a 27-28 foot trailer? Maybe. I'm not saying you need to buy a huge whomping truck, but I am definitely suggesting you learn from my experience before vs. after writing that big check.

Let's stipulate for the moment that ratings such as GVWR, GAWR, etc. actually matter (e.g. exceeding them for long is a pretty bad idea). If you don't accept that stipulation there's no point reading this post, as I'd just be wasting your time.

Given that stipulation, I'm learning the hard way that the stated load capacity for my 1/2 ton truck seems to have been largely fiction. My truck seems to weigh considerably more than stated, resulting in a substantially lower capacity than I had expected. To make matters worse, my AS tongue weight seems closer to 15% of the gross weight of the trailer than the 10% that AS suggests.

So, here's something I will be doing the next time I go through a TV/TT purchase:

• Before I buy my next TV, I will weigh it or a similarly equipped model on a CAT scale, preferably with a full tank of gas. Then I'll compute the actual load capacity by subtracting that weight from the GVWR for the TV.
• I'll subtract the claimed load capacity from the claimed towing capacity to ensure the TV I've selected can tow the gross weight of the trailer while it is also carrying the maximum possible load. This number may be incorrect but it should be wrong in the right direction, if you take my meaning.
• Next, I'll review the GVWR for my trailer and estimate the tongue weight at 15% of that value. AS says it's going to be about 10% (e.g. if the trailer has a GVWR of 7600 pounds, the tongue weight will be stated as roughly 760 pounds at that weight). Given my limited experience, the actual tongue weight will be 50% greater. At last check mine was at 15%. So, I'll use that as a ballpark figure and be closer to the truth when towing in the real world instead of on the pages of a glossy brochure.
• Then I'll put all the numbers together and ensure that a camp-ready rig fits comfortably within the TV's load capacity / GVWR as well as it's towing capacity. Again, I thought I had done my homework, but to my regret I did these computations based on bad information. Now I'm scrambling to find a solution that lets me avoid trading in my brand new truck for another TV, because that would be a really significant expense. (Trading in my TT for a smaller one isn't really an option, as I've spent the last 10 months working all the warranty-related kinks out of this one and I'm not anxious to through that again any time soon.)

Those of you who've been doing this towing thing for a while, have mercy. Numbers don't lie, but plenty of people I depended on when making a major purchase were apparently happy to do so to varying degrees...even though I repeatedly asked whether I was buying the right TV for the job. Remember, I never heard of this forum until after we bought our rig...

I got bad tongue weight numbers from AS (10% vs. 15% for tongue weight) and bad TV recommendations from my AS dealer (certainly a 1/2 ton truck is more than sufficient for that trailer). Then I used those numbers and ideas in combination with bad numbers from my truck dealer (claiming nearly 1,300 pounds of load capacity) to choose a very nice TV in the 1/2 ton range.

Ironically, I would have happily bought a beefier TV or a smaller trailer to make it all come out right...if I had been given realistic numbers and realistic recommendations, I could have made smart choices. Garbage in, garbage out.

Take my experience for what it's worth. I welcome your feedback and ideas, but would appreciate a minimum of "I told you so's" and fact-free opinions.

BTW, thus far our towing experiences have been really great, including an emergency stop and driving up/down over plenty of steep mountain passes and sharply winding roads without incident. We've seen zero symptoms of being at or above the GVWR for our TV. However, now that I realize how borderline we are wrt our TV's GVWR, I am trying to fit us reliably inside that envelope.

Those of you who are experts at towing 27-28 foot AS trailers with 1/2 ton trucks as TV's, I would love to hear your best weight management tricks. What's your GVWR and your real-world load capacity, and what cool things have you done to help keep your TV at or below GVWR while towing?

[dkottum]

Originally Posted by switz

When DOT does a stop, they do not care about the door sticker payload, they care about the axle ratings and do the tire ratings equal or exceed the axle ratings. If the scale weight on the axles is lower than their rating, then the vehicle is not overloaded.

The above is independent of the gross combined towing weight with is the total weight of tow vehicle and trailer when attached.

What DOT weigh station or patrol is stopping recreational Airstreamers? And what law applies to recreational Airstreamers? And when has a stop ever happened?

Are you applying commercial hauling/towing laws to us?

[xrvr]

Of course we could all buy one ton long bed crew cab diesel powered duallies and all of the payload and gross weight discussions are mute. But then this leads to a real can of worms on other issues. Jim

[crisen]

What seems to be almost missing from this is GCWR which is the real limiting factor for towing, there was one comment about a combined weight rating in one of the earlier posts. True axle weight rating is also important but since axles are normally sized to allow for some margin of safety IF you are within the other load limits.

Anyway back to my point about GCWR. This is the total limit of vehicle, payload and whatever you are towing. If you keep within the GCWR you will usually (always?) find that if you figure a tow vehicle at GVWR and subtract this figure from GCWR the remaining amount for the trailer is less than advertised towing capacity. If you want to utilize maximum tow rating and stay with GCWR you will find that the tow vehicle needs to be empty except for driver and fuel.

To help understand it you might look at the Ram tow calculator with the link in post 23. Take the first vehicle on the list as an example, a Ram 1500 SLT. It is advertised as having 1632 payload and max tow of 9250. Now open the calculator slide bar and play with the slider tab. This shows the GCWR of 14150. You will find that only a vehicle at curb (empty) weight gets 9250 tow, at gross weight with the full 1632 payload in the vehicle the tow rating is down to 7618. 9250 - 7618 is of course the 1632 you loaded into the truck. So just think about it as every pound of stuff you carry in the vehicle reduces the advertised tow rating by a equal pound.

[jcl]

Originally Posted by crisen

What seems to be almost missing from this is GCWR which is the real limiting factor for towing, there was one comment about a combined weight rating in one of the earlier posts.

Fully agree, but a qualifier is that not every vehicle has a published GCWR. For those that don't, the GCWR is the tow vehicle GVWR plus the trailer GVWR. Said another way, publishing a lower GCWR than that total is a way for a manufacturer to ensure that owners don't double dip, and tow at recommended limits while also loading the tow vehicle up, if that practice isn't supported by the manufacturer.

[Rocinante]

Hmm....if a TV has no published GCWR, then I think it doesn't have one. While adding these two values might be interesting, I suspect it doesn't represent a GCWR for a vehicle that doesn't have a published value.

I'd love to see a citation for that, as I'm happy to be shown wrong again. At this point it's quite obvious I've made big errors in this area, so one more or less doesn't further dent my pride.


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[jcl]

It is somewhat theoretical. It also comes from the commercial side. Personally, I think of a GCWR as I described it (sum of the GVWRs of the units in the combination) as the combination's GCWR, not the tow vehicle's.

The US Federal Motor Carrier Safety Regulations read:

Gross combination weight rating (GCWR) means the value specified by the manufacturer as the loaded weight of a combination (articulated) motor vehicle. In the absence of a value specified by the manufacturer, GCWR will be determined by adding the GVWR of the power unit and the total weight of the towed unit and any load thereon. (FMCSR 390.5)

That is slightly different than my definition, as it suggests trailer GVW, not trailer GVWR.

Google simply says:

The Gross Combination Weight Rating (GCWR) is the sum of all GVWRs for each unit in a combination-unit motor vehicle. Thus, for single-unit trucks there is no difference between the GVWR and the GCWR

Jeff

[Ron Gratz]

The FMCSR 390.5 definition of GVWR does not apply to recreational vehicles.
The Google definition also does not apply to recreational vehicles.

Ford defines "Gross Combination Weight Rating (GCWR): The maximum allowable weight of the towing vehicle, the trailer and all associated passengers, cargo and equipment."

Simply stated, the loaded weight of tow vehicle plus loaded weight of trailer should not exceed the GCWR. Or -- TVGVW + TTGVW < GCWR

The TV's GVWR and the TT's GVWR are not used to determine whether a TV/TT combination are within the TV's GCWR.

To simplify the determination of how much trailer weight can be handled by a tow vehicle, most TV manufacturers have created a term such as "Maximum Loaded Trailer Weight" (MLTW).
They then specify a value for MLTW for a particular TV configuration stating, for example, "Maximum Loaded Trailer Weight assumes a towing vehicle with any mandatory options, no cargo, tongue load of 10-15% (conventional trailer) or king pin weight of 15-25% (5th-wheel trailer) and driver only (150 pounds). Weight of additional options, passengers, cargo and hitch must be deducted from this weight."

That means the maximum allowable trailer weight is not equal to the MLTW value.
It means: TTGVW < MLTW - weight of additional options, passengers, cargo and hitch.
Or: TTGVW < MLTW - "extras".

For most TV manufacturers, the MLTW is approximately equal to a TV's GCWR minus the TV's "curb weight".
Unfortunately, to use the published MLTW value, you need to know the weight of "additional options, passengers, cargo and hitch".

The relationship is: MLTW = (GCWR - curb weight).
Or, TTGVW < GCWR - (curb weight + extras).
And, that's just another way of stating: TVGVW + TTGVW < GCWR.

GCWR specifies the maximum value for the amount of weight which the TV is moving down the highway.
TV GVWR specifies the maximum value for the amount of load the TV can carry on its tires -- but that's another thread.

Ron

[PharmGeek]

I'm lost and confused now


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[jcl]

Originally Posted by Ron Gratz

The FMCSR 390.5 definition of GVWR does not apply to recreational vehicles.

The Google definition also does not apply to recreational vehicles.

Ford defines "Gross Combination Weight Rating (GCWR): The maximum allowable weight of the towing vehicle, the trailer and all associated passengers, cargo and equipment."

....<snip>

I don't disagree. As I noted, GCWR is a commercial vehicle term wrt the regulations. It is also used by truck manufacturers to specify tow limits, considering tow vehicle loading and the impact that loading has on the published tow limit.

But the point was that not all manufacturers define the term for non-commercial vehicles. Perhaps they only define it when there is a good chance that the vehicle in question will be used for commercial purposes, I don't know.

And when they don't define it, we fall back on what the term actually means when the tow vehicle manufacturer is silent on the subject.

The poster I was responding to is from Washington state. A quick check of Washington State laws finds the following:

The GVWR of a combination or articulated vehicle, commonly referred to as the "gross combined weight rating" or GCWR, is the GVWR of the power unit plus the GVWR of the towed unit or units.

So his home state uses a definition similar to the federal one. And if he isn't a commercial vehicle, it doesn't much matter.

My home province doesn't define GCWR for non-commercial vehicles. The BC Motor Vehicle Act is generally considered one of the stricter ones, historically because of our mountainous terrain. They state that they don't regulate tow limits, but if they are exceeded that operators should check with their tow vehicle manufacturer in case there is a warranty aspect to exceeding them. In other words, they don't much care. They do care about GVWR of each vehicle, and about axle ratings.

Jeff

[kscherzi]

I once did all the math and worried and worried. Then I took the loaded rig to a CAT scale. Found I was under both front and rear axle ratings. After that I quit worrying and enjoyed camping.

[MrUKToad]

Originally Posted by kscherzi

I once did all the math and worried and worried. Then I took the loaded rig to a CAT scale. Found I was under both front and rear axle ratings. After that I quit worrying and enjoyed camping.

Nicely put. I was just thinking that we obsess too much about weight and ratings when we shouldn't.

[dkottum]

Originally Posted by MrUKToad

Nicely put. I was just thinking that we obsess too much about weight and ratings when we shouldn't.

Agree.