GVWR etc

[MollysMom]

I've truely tried to understand this but for some reason it's not getting into my head.  I may have it, but need to be sure.
I'm sort of looking at a 37' Allegro Bay - I'm trying to figure out how much of a load it will handle (not sure if that's the right term) Here is the info from the brochure 
GVWR 26,000
GAWR - front 10,000
GAWR - rear  17.000
GCWR 30,000
UVW 20,990  (I really don't know what this one is)
the dealer says I can tow 5,000 lbs - I don't see that anywhere on the brochure so not sure where he got that.
Is the weight I can load into the MH include the toad ?  I know I need to add in fluids but am not sure about the weight of the toad -  ??? ???I am SO confused !!
Thank you  ???

 

[baadpuppy]

Wow, one I can (hopefully) answer.

GVWR = Gross Vehicle Weight Rating and is the total amount of weight the vehicle by itself (not towing anything) can legally handle.

GAWR = Gross Axle Weight Rating and is the total amount of weight you can put on a particular axle.  Since you only list a front and rear axle, I assume there is no tag axle (3rd axle behind drive wheels).  If you exceed 10,000 pounds on the front axle or 17,000 pounds on the rear axle, you violate the specs and run the risk of damage.  Note that if you add them together you get 27,000 pounds.  Looks like the manufacturer has added a 1000 pound safety in there and also kept the GVWR below the 26,001 pounds that many places require a CDL for.  ;D

GCWR = Gross Combined Weight rating which basically is GVWR + tow capability.  Note that 30,000 - 26,000 is only 4,000, not 5,000.  Your dealer may be giving you the weight rating of the hitch (5000 tow, 500 tongue weight is common).  But to be a stickler for safety, you should limit yourself to 4,000 pounds towing.

UVW I believe is Unloaded Vehicle Weight, similar to dry or empty weight.  Basically, this is a ballpark number to help you determine approximately how much cargo capacity you have left.  You would subtract this from GVWR to get your cargo capacity.  26,000 - 20,990 = 5,010 pounds cargo capacity.  But, the problem is you don't know if they measured with full or empty tanks, etc.  In reality, you should fill all your tanks and go weigh the rig, subtract that from your GVWR, and use that as your cargo capacity.

Now, there are also some things you want to consider when towing.  That 4,000 pounds doesn't include any safety margin.  If it is a gasoline engine, you want a 20% safety margin out west, and 10% will do in the east.  For a diesel, I believe 10% is adequate on both coasts.  subtract 400 pounds for a diesel or a gasser in the east, 800 pounds for a gasser in the west.  That's either 3,600 pounds or 3,200 pounds, depending.

I believe I got everything correct.  Just 3 months ago I didn't know all this stuff.  I'm sure one of the experts here will correct any mistakes I made.

I believe there is room for "trading" some of your cargo capacity to your tow capacity, but honestly, I wouldn't play that juggling game.  It is too easy to forget you've done that and then exceed your GCWR without realizing it.

Sounds like you're making lots of progress with your search.

I really hope I was able to help.  Good luck!
jim

 

[Tom]

Our Glossary of RV terms explains what each of those means. This article in our library answers the question can I tow a dinghy?, and this article explains how to calculate the weight capacities and how much of a dinghy you can tow.  **

The short answer to your question is:

The coach has to be weighed to know the actual weight (or substittue the numbers in the example in the prior article). The towing capacity is simply:

GCWR - actual weight of the coach.

Alternatively, assuming you load the coach up to, but not above the GVWR of 26,000 lbs, your towing capacity is:

GCWR - GVWR = 30,000 - 26,000 = 4,000 lbs.

One caveat - you cannot exceed the hitch rating (e.g. if the hitch on the coach has a rating of 5,000 lbs, you can't tow more than 5,000 lbs no matter the other numbers say).

 

[MollysMom]

Jim, I may love you    Thank you for the info - it make sense.  I'm printing out your response and attatching it to the brochure for the Allegro.  Yippee !

 

[Gary RV_Wizard]

Technically it is incorrect to state that the GCWR is GVWR plus tow capacity. If the coach is not loaded to its full GVWR, then any leftover weight can be applied to the tow capacity.  Tow capacity is the GCWR minus the Actual Loaded Weight of the coach, subject of course to the rated limits of the hitch and the tow bar itself.

I suspect the dealer assumed you would load the coach much less than GVWR and gave you the hitch rating as the tow limit.  A risky assumption on his part, but par for the course for dealers/salesmen.

So your tow capacity should be at least 4000 lbs and might be as much as 5000 lbs, depending on how much gear, water, etc, you load into the coach.

 

[baadpuppy]

The thing I was most uncertain about was the 10%/20% factor for motorhomes.  I've seen it discussed for towing trailers, but I haven't read a thread where it was applied to motorhomes.  So my question is, do those rules of thumb still apply when talking about a motorhome?

thanks,
jim

 

[BernieD]

The dealer may have said that you can tow 5,000#s because he thought that there was a 5,000# capacity hitch on the coach. As others have said, there are many things that go into how much weight you can tow. I wouldn't even accept that the coach has a 5k tow hitch without verification. My first coach had a 3,500# hitch even tho the published specs called for 5k, the manufacturer did change it to a 5k hitch.

 

[Clay L]

Jim, I may love you    Thank you for the info - it make sense.  I'm printing out your response and attatching it to the brochure for the Allegro.  Yippee !

One number to pay close attention to is the CCC.
That's what you can put on board and carry in the motor home.

For weekend and short term use the CCC you will want is probably less than it would be if you full time.
We full time and have a CCC of 2800 pounds. We use all of it and wish we had another 700 pounds or so.

 

[Gary RV_Wizard]

The thing I was most uncertain about was the 10%/20% factor for motorhomes.

Jim, the theory still applies but in practice it is less significant when the towed weight is such a small proportion of the total combined weight. And motorhomes generally have big block gas engines or turbo diesels and the 10/20% margin is of less significance with them as well. The exception would be smaller B & C motorhomes with mid-size gas engines, e.g. the 6.0L Vortec.

Personally I do not use any margin if I can calculate ALL the actual weights involved and compare them to the GCWR. However I would still recommend staying well under the GCWR for performance reasons if the engine and drive train are relatively wimpy.  As a rule of thumb, we like to see about 1 HP for every 100 lbs of weight and a higher ratio is better.  For example, my coach has a GCWR of 42,600 lbs but the diesel engine produces a max of 370 HP, so my useful GCW is more like 37,000 lbs (100 lbs/hp) if I want decent performance. I'm currently running at about 37,500 and I wish it were 1000 lbs less, even with the potent 8.9L Cummins turbo diesel and 1200 ft lbs of torque.

 

[Carl L]

The thing I was most uncertain about was the 10%/20% factor for motorhomes.  I've seen it discussed for towing trailers, but I haven't read a thread where it was applied to motorhomes.  So my question is, do those rules of thumb still apply when talking about a motorhome?

thanks,
jim

The 10% number is a general precaution to account for loading, state of tune, state of maintenance, etc..   Nothing says you have to take it, it is a belt and suspenders thing.  The 20% is based on a more concrete factor:   Normally aspirated internal combustion engines lose 3% of rated horsepower per 1000 feet of altitude above sea level.   Most gasoline engines are normally aspirated.  Thus, for example, on the Colorado Plateau at Grand Canyon, at 6000 feet, your engine is running 18% below its rated HP.  In some of the Colorado passes you are over 8000 feet which robs you of 24% of your HP.  Combine that with miles long 6-8, even 9% grades both up and down and that 20% safety factor begins to look pretty lean.

Diesel engines, on the other hand, are mostly turbocharged and take a much lower hit at altitude, more like 1% per 1000 feet which can be ignored.  That said, out west with a diesel,  you would really like an engine brake on those long, long 6-8% downgrades.

 

[Ron]

Diesel engines, on the other hand, are mostly turbocharged and take a much lower hit at altitude, more like 1% per 1000 feet which can be ignored.  That said, out west with a diesel,  you would really like an engine brake on those long, long 6-8% downgrades.

I sure wouldn't want to be going down some of those grades without an Exhaust ot jake brake.  Things could go real bad in a hurry.