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Old 11-29-2012, 10:03 PM   #1
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Curb weight and GCVW, what is the difference?

Thanks to all of you who have so kindly answered all my previous questions. I have another one that has come up during my search for a tow vehicle: What is the difference between curb weight, gross vehicle weight and Gross combined vehicle weight for a toad? As I wrote in an earlier post I'm looking for a tow vehicle that can be towed behind a Tiffin Phaeton 36 QSH but also has the towing capacity to tow my 3500 lb boat when I need to. I'm considering a GMC Acadia. It has a 5,000 lb towing capacity, which I believe will satisfy towing the boat. The manual says the Acadia has a cub weight of 4676 lbs and a GCVR of 6679 lbs. I believe the towing capability of the Tiffin Phaeton 36 QSH is 10,000 lbs. So I'm assuming the Acadia will work for me as a toad?
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Old 11-30-2012, 04:02 AM   #2
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This will be a long post, but bear with me....

Curb weight (or base curb weight) is defined as the weight of the base vehicle as determined by the vehicle manufacturer. It usually also includes the weight of a full tank of gas, as well as engine oil and coolant. Base curb weight does NOT include the weight of any cargo, accesories, passengers or any options installed by the manufacturer during production. As you can see, base curb weight is almost never the weight of the vehicle as produced, due mainly to option content. And it certainly is not the weight of the loaded vehicle going down the road.

Gross vehicle weight is simply the weight of a vehicle as determined by a scale or as it is rolling down the road. It is variable based upon cargo and people on board, options installed, etc. It can vary from day to day, even hour to hour. The point is that GVW should not exceed GVWR....gross vehicle weight rating. GVWR is the maximum amount that the manufacturer has certified the vehicle can safely weigh, including itself, its cargo, its passengers and its options and accesories. GVWR not only addresses weight....it also addresses a vehicle's ability to operate safely at that weight level and to STOP safely as well. Multiple things are considered by the manufacturer in certifying a vehicle's GVWR.

I think the other term you are wrestling with here is Gross Combined Weight versus Gross Combined Weight Rating. Think towing capability and towing safety here. These terms are meaningful when comparing how much TOTAL weight is being moved down the road by a tow vehicle versus that tow vehicle's certified ability to move, to safely operate AND to stop that weight. We're talking about a tow vehicle AND a towed vehicle loaded and ready for the road, with all hands and stuff on board. GCW is usually the overlooked number when an RV'er concludes that his heavily-loaded rig is a nightmare when pulling AND stopping his also heavily-loaded toad/trailer....especially in the mountains! It is not uncommon for a tow vehicle to be within its GVWR and yet be well over its GCWR towing ability due to the additional weight of a heavily-loaded toad or trailer behind it. Happens all the time, especially out here in the West with our mountains. GCWR is about moving/stopping weight reliably and safely....not carrying weight as is GVWR. Both tow vehicle AND towed vehicle can be within their respective GVWR's....but the tow vehicle could easily be above/beyond its GCWR, due to the heavy load behind it. Make sense? Also, elevation must be considered when evaluating a vehicle's GCWR versus actual GCW. Elevation diminishes tow vehicle perfomance and increases vehicle braking requirments.

That 5,000 lb. Acadia towing capacity disappears rapidly if you have the vehicle stuffed to the gills with DW, 3 kids, camping gear, beer kegs and other heavy items. All of that weight must be moved and stopped, and it falls into the GCW versus GCWR as discussed above. That 6679 number you mention just can't be the Acadia's GCWR. If you are pulling a 3500 lb. boat, then the Acadia and everything in the Acadia should not weigh more than 3,179 lbs. Just no way that can be, methinks. You stated the Acadia's curb weight as 4676 lbs. The numbers don't work....

Sorry for the long post....but these are important things to consider IMO. Hope it helps. Suggest you look carefully at all of the numbers for your specific vehicles, especially GCWR. If I have mis-stated anything, folks, please let me know. Always willing to learn....
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Old 11-30-2012, 10:42 AM   #3
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GCWR is the max combined weight of the Acadia plus any trailer, including the gear in both and the hitch in between. GVWR is the max allowed weight ot the Acadia (and the trailer has its own GVWR as well - separate and independent of the tow vehicle).

As HeapBig says, the 6679 cannot be the Acadia GCWR. It is more likely to be the GVWR. I have a 2007 Acadia myself and that's pretty close to what mine shows for GVWR (which is 6400 lbs). If I add the front and rear axle ratings together, I get 6724 lbs, which is also close to your number. I've never been able to find a GCWR spec for mine - they usually don't specify that for cars and car-like vehicles - but an unofficial source shows it as 9500 lbs. That seems about right based on my 4900 curb weight and a 4500 lb tow rating.
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Old 11-30-2012, 05:06 PM   #4
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Gary....very helpful info, particularly re the weight numbers. A few more thoughts to the original poster....and I am NOT trying to argue any point at all! IMO, these are important things that anyone towing anything should consider.

Base curb weight, again, does not include the weight of passengers, cargo, vehicle options, accessories, hitch, etc. It is just base vehicle weight. Using your vehicle as an example for the OP, if you loaded your Acadia (including hitch weight) up to its GVWR of 6400 lbs. and you started pulling a 3500 lb. boat/trailer, your GCW would be 9900 lbs, 500 lbs over your vehicle's 9500 lb. GCWR. You're there! OP....make sense? And at 5,000 ft. elevation where we live, forget about it! GCWR should be reduced by 10% or so for every 1,000 feet of elevation due to diminished tow vehicle capability and increased braking requirements. At our place, your GCWR is now down by 475 lbs. to about 9025 lbs....a loss of 95 lbs. for every 1,000 feet. Leaving our neighborhood on your camping trip, you are getting close to being 900 lbs. over the vehicle's GCWR. Oh, and since you are going up over the summit which is 9,000 feet, you are now overloaded by 1255 lbs. And we see that all the time out here, believe me.

Re published GCWR's for vehicles, Ford (as an example) used to publish outstanding towing guide brochures that applied to all of their cars and light trucks. Don't know if they still do. If any car or truck was not recommended for towing, towing capacity and GCWR were not indicated. However, on any car or light truck where towing capacity was indicated, GCWR was always listed. Towing capacity can be very misleading if GCWR is not indicated. Seems to me that any manufacturer marketing towing capacity and not indicating GCWR would be in the middle of a legal minefield. I just gotta' believe there is a GCWR for an Acadia somewhere. But I may be wrong....and it wouldn't be the first time, that's for sure!
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Old 11-30-2012, 09:59 PM   #5
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According to this write-up on the 2013 Acadia (scroll down near the bottom of the page under "Capacities"), its GCWR is 10,450 Lbs. (for the AWD model) and its GVWR is 6,398 Lbs.

So 10,450 minus 6,398 = 4,052 Lbs.

Doesn't that mean that even if the Acadia is loaded to its maximum weight (GVWR), that it can still tow the 3,500 Lb. boat and trailer?

We're thinking that you should be okay on all accounts. You should be able to easily tow:

1. the Acadia behind the Phaeton,

2. the boat and its trailer behind the Phaeton,

3. the boat and its trailer (assuming 3,500 Lbs.) behind the Acadia

You just won't (or shouldn't ) tow both the Acadia and the boat behind the Phaeton at the same time --double tow both at once behind the Phaeton.

Are we thinking correctly assuming that the specs in that article are accurate?





(Article is attached to this post in a PDF in case the link doesn't work ..."Capacities" is at the bottom of page 3)
Attached Files
File Type: pdf 2013 GMC Acadia.pdf (518.6 KB, 33 views)
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Old 12-01-2012, 12:30 AM   #6
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The figures from our above post see to be confirmed. See the PDF attached downloaded directly from the GMC website to confirm (last two pages under "Capacities").

Maximum Towing Capacity is listed as 5,200 Lbs. That seems to suggest that even though the GCWR is 10,450 Lbs., if the Acadia is loaded to its maximum weight (its GVWR of 6,398 Lbs.), that you can tow a maximum of weight of 4,052 Lbs. but if the Acadia is loaded to somewhere under its GVWR, then the weight you tow should NOT exceed 5,200 Lbs.

It still sounds as if you are okay to tow your boat behind your Acadia as even if your boat and trailer should by some chance approach the 4,052 Lb. weight, you may be able to lighten the load in your Acadia so that the "combined weight" doesn't exceed the 10,450 Lb. limit. Leave behind those two kegs of beer, the three kids, and the DW and that should do it.

But again, it sounds as if even if you did load the Acadia to its maximum, you should still be okay to tow the boat if it does in fact weigh under 4,052 Lbs.
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File Type: pdf 2013-GMC-Acadia-Technical-Specifications.pdf (80.7 KB, 24 views)
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Old 12-01-2012, 02:32 AM   #7
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amanda h....very interesting info on your part! Good stuff....

Re your first post, my opinion is "Yes" to all 3 statements based upon the weight data you presented. After all is said, that is really what the OP is trying to figure out. If he is operating at higher elevations like we have, his "cushion" can be reduced significantly as I mentioned previously.

Re towing both vehicles behind the Phaeton, believe it or not, it is legal in some Western states, I believe, to pull 2 vehicles in tandem. I sure wouldn't do it....but some folks do. I ain't going there in this discussion....

Re your second post, the Acadia's towing capacity of 5200 lbs. sounds quite adequate for his needs. But as I said earlier, rated towing capacity can be misleading. If he pulls his cousin's new boat and trailer that weighs 5,200 lbs, then the Acadia's fully loaded weight going down the road (GVW) should not exceed 5,250 lbs. (10,450 lbs. GCWR minus 5,200 lbs. for boat and trailer = 5,250 lbs max GVW going down the road). That max. 5,250 GVW is a long way (1,148 lbs.) from the Acadia's GVWR of 6,398 lbs. That's why a vehicle's rated towing capacity can sometimes be misleading. And that's also why high elevations can become one's worst nightmare if not considered.

Again, we are talking about moving and stopping TOTAL weight here, not just the weight of the towed vehicle. In the 5,200 lbs. example above, I would opt for leaving behind the cousin, the DW, the kids and just about everything else but the toothbrush. But certainly NOT the 2 kegs. We need that for safety sake too....right??

Good stuff. Sure hope all of this "junk" I/we're tossing around is helping the OP.
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Old 12-01-2012, 11:10 AM   #8
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Right, Amanda. You must not exceed the GCWR, so loading the car to or near the GVWR reduces the tow capacity in most vehicles. The Max tow rating is calculated based on a vehicle that has only full fuel and a federal standard 154 lb driver, so additional weight in the tow vehicle usually results in a reduction of available tow capacity in order to stay within the GCWR.

The Phaeton probably has enough GCWR to tow both the Acadia and the boat trailer, but a "double tow" is not legal in all states. Check the state laws before attempting it. Furthermore, a tow bar with a 10,000 lb rating would be required to connect the Acadia to the motorhme.
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Old 12-01-2012, 11:28 AM   #9
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Originally Posted by HeapBigEngin View Post
... And at 5,000 ft. elevation where we live, forget about it! GCWR should be reduced by 10% or so for every 1,000 feet of elevation due to diminished tow vehicle capability and increased braking requirements.
HeapBigEngin, I'm curious, how does braking reduce at elevation? I certainly understand engine changes, but brakes? Are you talking about air brakes at elevation become less effective? Auto brakes are hydraulic with vacuum assist, are you saying they become less effective? Brakes work by friction and I don't see friction changing at elevation.
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Old 12-01-2012, 03:35 PM   #10
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Quote:
Originally Posted by BFlinn181 View Post
HeapBigEngin, I'm curious, how does braking reduce at elevation? I certainly understand engine changes, but brakes? Are you talking about air brakes at elevation become less effective? Auto brakes are hydraulic with vacuum assist, are you saying they become less effective? Brakes work by friction and I don't see friction changing at elevation.
Simple answer, really. Gravity....and its impact on vehicle speed and momentum when coming down from high elevations. Braking doesn't reduce at elevation....braking requirements increase at elevation.

You are right. It's not the elevation per se that affects the internals of a braking system in any meaningful way. No question there. Rather, it's the increased vehicle speed and momentum caused by gravity as a vehicle descends from elevation that increases the work the brakes need to do to slow and stop the vehicle. That increasing downhill speed can be viewed as increased vehicle energy. And that increasing speed - energy - must be adressed by the engineers via an adequate braking system up to the task of controlling that speed....or energy. Obviously, the higher the weight load, the higher the vehicle energy being generated coming down from elevation. Thus, an overloaded situation not only strains the vehicle's powertrain capacity, but it severly strains its braking capacity....especially at elevation. Make sense?

None of the above might matter to those folks who never operate in hills or mountains. But many of us love to get up into the foothills and/or the mountains. And most of us gotta' back down eventually. And where I live in the West, we have many, many hills and mountains to navigate on a typical journey. And those brakes need to be up to the task.

I think I'll go now and open one of the kegs and pour me and DW a couple of tall, cool ones.

BTW...I love your "tag" of being pushed by a '00 Beetle. That's great! Take care...
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Old 12-01-2012, 06:02 PM   #11
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DH is really getting into this whole discussion but also thinks that maybe you guys are over-thinking the OPs question. I'm not really into towing issues as it's more of a "guy thing" but I enjoy helping DH analyze all RV issues no matter what they are.

This is a summary of his thoughts:

What we now know:

Phaeton 36 QSH GVWR: 36,000 Lbs.

Phaeton 36 QSH GCWR: 46,000 Lbs.

Therefore the towing capacity of the Phaeton is: 46,000 minus 36,000 or 10,000 Lbs. (this is assuming that the Phaeton is loaded to its maximum capacity or its GVWR and if so, the coach can tow up to 10,000 Lbs.)

GMC Acadia curb weight: 4,850 Lbs. for AWD model

GMC Acadia GVWR: 6,398 Lbs.

GMC Acadia GCWR: 10,450 Lbs.

Therefore the towing capacity of the Acadia is: 10,450 minus 6,398 or 4,052 Lbs. but not to exceed 5,200 Lbs. (this is assuming that the Acadia is loaded to its maximum capacity or its GVWR and if so, it can tow up to 4,052 Lbs. However, if it is not loaded to its GVWR, then the amount it is towing should not exceed 5,200 Lbs.)

OP's boat and trailer: 3,500 Lbs.

Conclusion:

1. The Acadia can easily be towed behind the Phaeton as it should weigh no more than its GVWR which is 6,398 Lbs. Again, the Phaeton's towing capacity is 10,000 Lbs. therefore the Acadia weighing less than 10,000 Lbs. can easily be towed behind the Phaeton with 3,602 Lbs. to spare.

2. The boat and trailer can easily be towed behind the Phaeton as we are assuming that the boat and trailer weigh 3,500 Lbs. Again, the Phaeton's towing capacity is 10,000 Lbs. so the boat and its trailer can easily be towed behind the Phaeton with 6,500 Lbs. to spare.

3. The boat and it's trailer can easily be towed behind the Acadia as the Acadia's towing capacity when it is loaded to its maximum weight (or its GVWR) is 4,052 Lbs. So the boat and its trailer should be able to be towed behind the Acadia even when the Acadia is loaded to its maximum weight as the boat and its trailer weighs 3,500 Lbs. which is under the 4,052 Lbs. towing capacity of the Acadia by 552 Lbs.

4. The Phaeton towing both the Acadia and the boat and its trailer at the same time could be done in states which allow double towing but the cargo contained by the Acadia would have to be limited to under 1,650 Lbs. (10,000 Lbs. minus 3,500 minus 4,850 = 1,650 Lbs.) However, the tow bar going from the Phaeton to the Acadia would have support such a towing configuration. Personally, we'd be rather nervous about using a traditional tow bar and baseplates on such a towing configuration. We'll leave that advice to the real experts. However, I'm not so sure that the OP was even considering towing both the Acadia and the boat at the same time behind his Phaeton. Did anybody else interpret that he wanted to do that?

We're thinking that all other factors will not really play into the equation for as long as you keep the weights under the manufacturer's ratings, factors such as braking capacity or altitude, etc. shouldn't be too much of a worry. Or should it?
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Old 12-02-2012, 02:25 PM   #12
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Thanks to everyone who took the time to respond to my original post. You have given me some excellent information and advice. I really appreciate it!
Just to clear up some of the questions brought up in some of your responses: No we do not plan to double tow our boat and the Acadia behind the Phaeton. That would be way to scary!
Also, I doubt that we will ever be driving the Acadia with at it's 6,398 lb GVWR when towing the boat since it is just my husband and I and we're both average weight people and we travel pretty lightly.
It sounds like the Acadia is the toad that will meet all our needs: It can be towed 4 down behind the Phaeton and it can tow our boat when we want to go fishing without taking the RV or just taking the boat in for service without having to hook it up to the RV.
Thank you everyone for helping us make this decision!
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Old 12-02-2012, 02:38 PM   #13
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amanda h, your explanation is excellent and spot on.
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Old 12-02-2012, 06:11 PM   #14
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GCWR should be reduced by 10% or so for every 1,000 feet of elevation due to diminished tow vehicle capability
Most any modern vehicle with computer-managed air/fuel ratio will not suffer any degradation in power up to around 5000 ft or so. It constantly monitors air mass so it can compensate for the thinner air at higher altitudes, and will successfully do so as long as it can suck in enough total air volume to get the required amount (mass) of air. Most vehicles can do that to at least 5000 ft and probably more in most cases. 8000 or 10,000 ft is probably a different matter, though.
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