Why the discrepancy? (long)

[Thoss]

I have found many different versions for figuring the perfect match for a tt and tv. ?But not everyone agrees.

For example Brent Peterson in his book "The Complete Idiot's guide to RVing" states (p223) "The GVWR is the towables absolute limit and the magic number for tow vehicle/towable matchmaking." ?

Yet, Bill Estes in "The RV Handbook" (p188/189) states, " When selecting a new trailer, refer to the UVW rating if the trailer was built after late 1996; otherwise , add the manufacturer's dry-weight listing to your personal estimated weight of water, propane, and all supplies for an estimated actual weight of the trailer, loaded for a trip."

I've even had people give me different formulas, such as:

80% of your GCWR

or

GVWR - GVW = hitch weight, GCVWR - GVW - ppl&cargo = trailer gross weight

or 10-20% of GVWR

Why is there such disparity among RV ppl?! ?I'm driving my wife nuts with all the figures.

So here's my rig and how each formula persuades:

2001 Chevy Silverado Extended cab, short box 2wd 4.8L v8 Axle 3.42 (6,300#) I don't believe I have the 3.73 axle ratio GVWR =6200 (even though book says 6300, 6200 is stamped on the door) GAWR Frt =3,600 GAWR RR = 3,686 ?GVW 4,760 GCWR 11,000

Ok, formula 1 GCWR * .80 ---- 11,000*.80 = 8,800 (wow!!)

formula 2 GVWR -GVW = hitch weight GCVWR - GVW - ppl&cargo
? ? ? ? ? ? ? 11,000-5480= 720 hitch weight, 11,000-4760-720=5520 max trailer weight

formula 3 10-20% of GVWR, 6200*.80=4960 max trailer weight

I've been using the 4,960 figure while shopping. ?I find it sort of seductive to go with the higher 5520 weight which is ~90% of my GVWR. ?But alas I'm in Northern Cal. many mountains.

So basically why isn't there a silver bullet, one figure? ? ??? It seems very perplexing for a newb, lol.

 

[Gary RV_Wizard]

I've even had people give me different formulas, such as:

80% of your GCWR

or

GVWR - GVW = hitch weight, GCVWR - GVW - ppl&cargo = trailer gross weight

or 10-20% of GVWR

Well, I think you can ignore those people, at least the ones that say a percentage of something.  But generally all thosse numbers are talking about difering aspects of towing and they aren't reallyin conflict with each other.

I don't have time for a detailed answer right now, but basically we assume that most trailers will be loaded to or close to its GVWR. That's what Brent Petersen is saying you should plan for.  The GCWR stuff has to do with how much your truck is able to tow and has to be compared against the trailer GVWR to determine safe and practical loads.

More later, unless someone else jumps in with further details.

 

[Thoss]

Thanks, all those numbers were driving me batty! 

 

[Carl L]

You are just comparing trailer weight to truck tow capacity.

I thoroughly agree with Bill Estes, that the trailer weight number that should be used is Gross Vehicle Weight Rating which consists of the trailer vehicle weight plus the maximun cargo it should carry.? ?Dry weight is just a estimated weight that may not include A/C units, awnings or certain appliances - in short all the optional stuff.? GVWR is a the weight you should not exceed on the trailer and can be found on the DOT plate of the trailer.? ?The only thing better is the actual weight loaded for travel as determined on a scale.? That is not usually available on new or even used trailers.? It is something you usually can? find out only after buying a unit.? ?The GVWR is always available is the conservative number you should go with.?

Truck tow ratings are found in the maker's owners manual, website, or in the Trailer Life Tow Ratings tables on their website.? The rating is based on engine, transmission, rear end ratio, suspension, vehicle weight, cooling systems, and brakes.? ? We like to discount that a bit, say 10% for aging of components, and just general conservative approach to a safety issue.

However, out in the mountain West and Pacific Coast there are miles and miles of road above 6000 feet and passes that actually top at 11,000 feet.? ?An unsupercharged engine will lose 3% of its HP for every 1000 feet of elevation.? You will be hauling that trailer with only 82% of your sea level power at 6000 feet on the Colorado Plateau.? Make? that 67% getting over that 11,000 foot Monarch Pass in CO.? Therefore we boost the tow rating safety factor to 20%.? ?Not only will altitude affect you, but there are long long 6%, 8% grades even on interstates in the west.? Remember brakes and cooling systems are a factor in tow ratings.

In hunting for truck and trailer make sure that your trailer GVWR is no more that 90% of you truck's tow rating for towing east of the Rockies.? ?Make that 80% if you want to tour the Rockies, US SW, or Pacific Coast

Eastern US:? ?Trailer GVWR should be 0.90 x Tow rating .
Western US:? Trailer GVWR should be 0.80 x Tow rating.

Tongue weight is a concern.? But differently.? ?It is already included in tow ratings so do not add it to trailer weight in calculations -- it is all ready in there.

In travel trailers, it should be no less than 10% of trailer weight, that is critical for trailer stability.? ?It can be as much as 15-16% but that not critical.?? Axle loading is not usually a factor in TTs -- the weight distributing hitch distributes the tongue weight to all truck axles.

In 5th wheel the pin weight, which is analogous to the TTs tongue weight,? is of concern.? It should not exceed the gross axle rating of the rear axle(s).? ?5ers usually have a pin weight in the 15-20% of trailer weight range.? That makes a consideration of pin weight a matter of concern -- especially for trucks in the 1/2 ton range.? ?It is also the reason that many people who haul big 5ers use 1 ton trucks or even medium duty trucks with dual rear axles.



?

 

[Gary RV_Wizard]

I see Carl has answered in more detail, so I won't muddy the waters further with more generalities.  You probably have further questions, though, so feel free to ask.

 

[edubb]

In travel trailers, it should be no less than 10% of trailer weight, that is critical for trailer stability.  It can be as much as 15-16% but that not critical.  Axle loading is not usually a factor in TTs -- the weight distributing hitch distributes the tongue weight to all truck axles.

I notice that the 2004 Trail Lite brochure gives a hitch wt of 271lbs for a 3987lb total dry weight (model # 8263s).  This would be only 6%.  About that same percentage for several 2004 models, naturally one I was considering...

Should I avoid the 8263s because of this?  Thanks.
-Eric

 

[Carl L]

I notice that the 2004 Trail Lite brochure gives a hitch wt of 271lbs for a 3987lb total dry weight (model # 8263s). This would be only 6%. About that same percentage for several 2004 models, naturally one I was considering...

Should I avoid the 8263s because of this? Thanks.
-Eric

Looking at the 2007 brochures on line, the same seems to be true of all in the line bar two.  Myself I would be suspicious of the unit's stability under stress.  If I were to buy one, I would want a lot of headroom on tow ratings.  I would try to load it nose heavy and if the freshwater tank is ahead of the axles, I would never travel without a full tank.  I might also consider a Hensley Arrow hitch.  The unit is probably too light for a Reese Dual Cam system.

But then I am a cautious soul as you may gather from my postings here.

 

[Gary RV_Wizard]

I wouldn't pay much attention to dry weights and related hitch weights. The only weight that matters is the weight when you go down the road and most trailers gain substantial weight up front when loaded.

 

[edubb]

Thanks for the help.  Where is the fresh water tank normally, in an ultralite?  Under a dinette seat?  I've looked underneath a few trailers and saw only the grey and blackwater tanks.
-Eric

 

[Carl L]

Hopefully your fresh water tank will be ahead of the axles.  Look for where the fill inlet or drain plug is located.

 

[Lou Schneider]

Another point - most of the pickup tow ratings assume 60 sq. feet of combined truck and trailer frontal area.  That's about the size of a horse or utility trailer.  A 8 ft wide x 12 ft. high RV trailer has 96 sq. feet frontal area - over 50% more than what the tow ratings assume.

More frontal area = more wind resistance, which means you need more horsepower to move it down the road.  A truck that's towing at it's maximum rating doesn't have much power left to pull that big sail down the road.

 

[edubb]

Another point - most of the pickup tow ratings assume 60 sq. feet of combined truck and trailer frontal area.  That's about the size of a horse or utility trailer.  A 8 ft wide x 12 ft. high RV trailer has 96 sq. feet frontal area - over 50% more than what the tow ratings assume.

More frontal area = more wind resistance, which means you need more horsepower to move it down the road.  A truck that's towing at it's maximum rating doesn't have much power left to pull that big sail down the road.

That's interesting.  I wonder what they assume for drag coefficient, which can vary a lot depending on shape, roughness, and whether you remembered to roll in the awning.... 

I do know that a salesman told me he sold a 6500lb fifth wheel to a guy with a Dodge Dakota, and it was "no problem--he put airbags on his truck."  By the time he and his family pack their coolers with beer and weinerschnitzel, then pile into that Dakota, he'll be 2000lbs over the GVWR and GCWR. 

My Dakota might be rated for 6000lb towing, but a 4000lb trailer is more realistic when you consider people and gear.  Even then, it wouldn't be too hard to reach the GVWR and GCWR....truck 4400lb, trailer 4100lb, water/beer/people/beer/gear 2000lb, your right at the maximum recommended for the Dakota 4.7L 2WD Quad Cab with 3.92 rear end...

 

[bdcolvin]

...I don't have time for a detailed answer right now, but basically we assume that most trailers will be loaded to or close to its GVWR....

This raises an interesting question.  I am a "pre-newbie" i.e., I am just starting to look and will almost certainly rent before I buy.  I know some will discount the importance of the numbers, but I am extremely conservative and if the numbers don't look good I will shy away.  I have been researching lightweight (up to 7000# GVWR) TTs and have complied manufacturer specs for about 100 models of interest in a spreadsheet.  I have seen some models (e.g. Cruiser Fun Finder X-210) with a CCC actually higher than the UVW (3505# vs 3495#).  I can't imagine loading 3500# fluids/options/gear in a 3500# UVW / 7000# GVWR trailer.  So does this mean the frame, suspension, and tires are unnecessarily stiff?  Does this make for a harsh and bouncy ride that will pound on the structure and contents?  In my 100 TT sample the average and median CCC to GVWR ratio is only 35%.  Should I be concerned about this?

 

[Carl L]

This raises an interesting question.  I am a "pre-newbie" i.e., I am just starting to look and will almost certainly rent before I buy.  I know some will discount the importance of the numbers, but I am extremely conservative and if the numbers don't look good I will shy away.  I have been researching lightweight (up to 7000# GVWR) TTs and have complied manufacturer specs for about 100 models of interest in a spreadsheet.  I have seen some models (e.g. Cruiser Fun Finder X-210) with a CCC actually higher than the UVW (3505# vs 3495#).  I can't imagine loading 3500# fluids/options/gear in a 3500# UVW / 7000# GVWR trailer.  So does this mean the frame, suspension, and tires are unnecessarily stiff?  Does this make for a harsh and bouncy ride that will pound on the structure and contents?  In my 100 TT sample the average and median CCC to GVWR ratio is only 35%.  Should I be concerned about this?

Not really.  Trailer ride is not too sigificant.  First of all, most trailers never leave the paverment outside of a campground.  Secondly, trailers by their nature do not rack up the miles like a motor vehicle.  They are hauled to a location and unhitched.  Thirdly, the tongue weight transfers some of the energy to the tow vehicle's  suspension. 

All that said, we all learn to bolt stuff down before we hitch up and hit the road and not many of us transport glassware and fine china -- more like melmac, stainless steel and Corningware.

 

[bdcolvin]

Thanks for the insight.  I guess this leads to another question...if 2500# is a more practical maximum payload for this specific example and I swore on my grandmother's grave not to load more than that, would it be dangerous to treat it like a 6000# GVWR trailer for selecting a tow vehicle and hitch?  Or should I stick with the manufacturer's (grossly overstated IMO) GVWR?

 

[Carl L]

Shoot you can do anything you want.  However, most old timers around here will tell you that junque tends to grow so as to fill the space available to stuff it into.  Bill Estes, the guy who wrote the book says use GVWR.  I say use GVWR.  For one thing it is a real number, one that is engraved on the trailers DOT plate and is available in one form or the other in mfr. specs.  The only better number is the actually scaled weight of the unit with all fluids and junque on board and ready to travel.  That number is a bit hard to get on a trailer that you don't own yet tho.  Your guess or my guess on what you will add to a somewhat dubious dry weight listed by a manufacturer?  That ain't worth nada.

 

[otrider]

Hi all,  I've been missing being able read all the ? and answers but I've been a busy girl!  House is empty, and renters moving in!  I'm now living in my 5er!  Will take off on the 20th for Holiday, Florida for a brief visit with aunt and cousin then on to Fort Pierce for 13 weeks.  I'm psyched!    Now for my ? 

Tow vehicle  Ford F250 V10 4wd 
Tow Rating 12,500

Trailer 30' fifth wheel
GVWR 12,000

Had the whole thing weighed last Sat and I think everything is good but with the pin weight and axle weight etc.  I'm confused  ??? all over again. I went with a truck driving instructor who  said they won't let you unhook from the trailer and weigh them seperately so I'm relying on my panel of experts for the final approval or I start pitching stuff out the door of the trailer!  Here are the results:

Steer axle 4,360
Drive axle  5,580
trailer axle 9,580  (no propane and no water)
Gross Weight 19,520  Help!

Thanks

 

[Carl L]

Hi all,  I've been missing being able read all the ? and answers but I've been a busy girl!  House is empty, and renters moving in!  I'm now living in my 5er!  Will take off on the 20th for Holiday, Florida for a brief visit with aunt and cousin then on to Fort Pierce for 13 weeks.  I'm psyched!     Now for my ? 

Tow vehicle  Ford F250 V10 4wd   
Tow Rating 12,500

Trailer 30' fifth wheel
GVWR 12,000

Had the whole thing weighed last Sat and I think everything is good but with the pin weight and axle weight etc.  I'm confused  ??? all over again. I went with a truck driving instructor who  said they won't let you unhook from the trailer and weigh them seperately so I'm relying on my panel of experts for the final approval or I start pitching stuff out the door of the trailer!   Here are the results:

Steer axle 4,360
Drive axle  5,580
trailer axle 9,580  (no propane and no water)
Gross Weight 19,520   Help!

Thanks

I assume that you weighed fully loaded ready to travel except for propane and water.  I am further assuming that you weighed the trailer unhitched from the truck as we state in the weighing procedure in the library.

Taking a 10% safety factor on your truck's rating, you should be ok towing 11250 lbs.    Out west with its high altitudes and long grades you should take 20% and would be ok towing 10,000 lbs.  Cutting to the chase, you are good to go.  Propane and a full water tank should not exceed your limts any where in North America. 

Enjoy.

 

[Gary RV_Wizard]

Apparently, Carl, he did not unhitch the trailer. The weight given would appear to be trailer axle weight with the king pin still resting on the truck. Since we don't know what either the truck or the trailer weighs by itself, we can't calculate all the weights or know if he is within the 12,500 lb tow rating (whether with ort without a safety margin).

However, we could evaluate the rear axle GAWR vs load and the GCWR vs total gross weight, if we knew what those were.  Using the 2005 Ford Towing guide as a reference, it looks to me like a V10 4WD should have at least a 14,200 lb tow rating for fifth wheel towing (not 12,500, which is the rating for a travel trailer) and a minimum GCWR of 21,000 lbs. Otrider is in pretty good shape on gross weight if that's what her truck is.

Otrider: check your rear (drive) axle GAWR, which should be on a plate attached to the driver's door post or on a sticker in the glove box.  It needs to be less MORE than the actual 5580 lbs you weighed, preferably with some extra margin since the weight will surely go up when you add some water and the inevitable extra goodies.

[edit]Corrected GAWR advice - "less" should be "more"[/edit]

 

[Alaskansnowbirds]

Otrider: check your rear (drive) axle GAWR, which should be on a plate attached to the driver's door post or on a sticker in the glove box.  It needs to be less than the actual 5580 lbs you weighed, preferably with some extra margin since the weight will surely go up when you add some water and the inevitable extra goodies.

Gary,

I think you meant the GAWR needs to be MORE than the 5580 weight.

[edit]Right you are - thanks!  [Gary][/edit]