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Old 09-09-2014, 07:07 AM   #29
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Originally Posted by switz View Post
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?
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Old 09-09-2014, 07:28 AM   #30
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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
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Old 09-09-2014, 09:06 AM   #31
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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.
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Old 09-09-2014, 07:35 PM   #32
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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.
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Old 09-09-2014, 10:07 PM   #33
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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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Old 09-10-2014, 02:10 AM   #34
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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

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Old 09-10-2014, 04:40 PM   #35
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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.

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Old 09-10-2014, 05:05 PM   #36
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Old 09-10-2014, 05:28 PM   #37
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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:

Quote:
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.
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Old 09-10-2014, 06:17 PM   #38
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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.
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Old 09-10-2014, 06:27 PM   #39
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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.
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Old 09-10-2014, 06:45 PM   #40
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Nicely put. I was just thinking that we obsess too much about weight and ratings when we shouldn't.
Agree.
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Old 09-10-2014, 11:44 PM   #41
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Thanks for that input, much appreciated. We are under both GAWRs, we are way under the official GCWR, and we are well under GVWR for the trailer. So, maybe we should just stop worrying so much, because our towing experience has been stellar.

It does sound suspiciously like a subtitle to Dr. Strangelove, though: "How I learned to stop worrying and love my tow vehicle."

In any case, it's probably a good idea to regularly go through the trailer and toss out any redundant stuff, put heavy things where they will generate the best balance, keep the fresh water tank mostly empty unless we know for sure we're going to need it at our next stop, and keep looking for ways to improve the towing experience. I'm glad we made that effort, even if we decide to stop worrying so much about the TV's GVWR.
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Old 09-11-2014, 12:43 AM   #42
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in any case, it's probably a good idea to regularly go through the trailer and toss out any redundant stuff, put heavy things where they will generate the best balance, keep the fresh water tank mostly empty unless we know for sure we're going to need it at our next stop, and keep looking for ways to improve the towing experience. I'm glad we made that effort, even if we decide to stop worrying so much about the tv's gvwr.
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