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GBlack
Evansville, Indiana
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Joined: 08/10/2006
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Hi: First, thanks to those who've hung in with me on recent threads while I attempt to figure out this towing stuff. Please bear with me.
1) My 09 Highlander has GVWR of 5800 lbs, curb weight of 3979 lbs, stated payload of 5800-3979 = 1821 lbs, and max tongue weight of 500 lbs. The 1821 lb payload includes both passenger/cargo weight AND tongue weight. So if my passengers/cargo only add up to (for example) 1000 lbs, does this mean my "real" tongue weight limit = 1821 - 1000 = 821 lbs? In other words, does the tow vehicle know the difference between passenger/cargo weight and tongue weight? Or does the SUM of those two forces (weights) matter more than the two INDIVIDUAL weights?
2) I read the following on ToyotaNation Forum where somebody posted a reply from Toyota Customer Service saying a weight distribution hitch (WDH) isn't compatible with a Highlander since it will put too much strain on its unibody construction. Has anybody else heard of a situation where a 5000 lb tow rated vehicle is not compatible with a WDH? Here's the quote, supposedly from Toyota Customer Service:
"We would like to take this opportunity to mention that most hitch manufacturers only recommend weight distribution when towing over 5000 pounds; the 2009 Highlander has a maximum towing capacity of 5000 pounds. Weight distribution hitches put a great deal of strain on the frame of the vehicle to achieve the distribution of the weight. Unibody vehicles are not built for this type of strain; the Highlander is a unibody vehicle that does not have a full frame, it is not recommended for use with a weight distribution hitch."
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blt2ski
Kirkland, Wa
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What you have said is true, ie if you have 1821 lbs of total payload, put in 1000 lbs of people and other junque, then the remaining to a degree is what you have availible for hitch wt.
"ISSUES" with the fact you can not use a WD....ie wt from the hitch on the rear bumper (area) will take some weight off the FA< so reality is, you may only have or want about 600 lbs of hitch wt using your weight number example. The amount taken off the FA will then load up the RA.
Some rigs this may be a bunch of wt off the FA, real life example, my equipment trailer has a 1500 lb HW to it. I put it on my 2000 C2500 reg cab with a 135" WB, and some 1000+ lbs is taken off the FA! On my crew cabs, about 200-300 lbs is taken off with 170" WB's, then my dumptruck, with a 15K RA, and 188" WB, all of 60 lbs comes of the FA< ALL examples of what happens with the same trailer hooked up. "SO" until you know how much wt will come off the FA< I am not sure I would want to put 800 lbs on the RA hitch area. Hence why 500-600 lbs would be better!
It would be nice if you could use a WD, even if you limited the amount of wt transfer to half what one might do with a full frame rig, like my pickup.....it would help.......for handling and some other issues. BUT< it is NOT needed "IF" you have a properly balanced trailer etc. The latter is the main key to happy towing.
Hope this makes sense.
marty
05 Chev CC D/A LS Dooley
92 Navistar dump truck, 7.3L 7 sp, 4.33 gears with a Detroit no spin
00 Chev C2500, V5700, 4L80E, 4.10, base truck, no options!
92 Red-e-haul 12K equipment trailer
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Chuck&Gail
In the Colorado Mountains
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Joined: 06/16/2004
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IMO 500# maximum tongue weight is really very clear. Maximum tongue weight is 500#. Note you want about 13% of TOTAL LOADED trailer weight on tongue, so you should not tow a trailer over about 3800#. Why so light? Cause you have no frame, so tongue weight is supported by unibody.
Each spec is important. IMO NEITHER should be exceeded.
Some unibofdy will take twist of WD hitch, which pushes UP on rear of TV, and DOWN on front. Non-WD hitches do the opposite, they push DOWN on rear causing FRONT of TV to go UP.
Just my two cents, and worth that.
Chuck
Wonderful Wife
Lovely German Shepherd.
1999 Mercedes ML320 TV
2003 Wanderer 187TB Toybox (3620# UVW, 4800# loaded)
Not yet camped in Hawaii, 2 Canada Provinces, & 2 Territories.
I can't be lost because I don't care where this lovely road is going
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smkettner
Southern California
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Joined: 03/21/2005
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If the tongue weight max is 500 pounds there is no further math needed. Yes the vehicle can tell the difference between 821 pounds focused on the hitch vs spread around and distributed through the vehicle.
You can probably lift 80 pounds using both arms right? Now do that with two fingers and you will understand the difference of how the stress is distributed.
Same type of focused stress when you add the WDH and your vehicle is not engineered to take that stress.
2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
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Road Ruler
Canada
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Many import manufacturers don't seem to have a clue about WDH's.
The Honda Ridgeline for example is one of the best built, heavy duty, unibodied vehicles built today yet the manual says they too do not recommend the use of a WDH.
LOL, Hummmmmmm....... Honda Ridgeline towing forum
Airstreams.... the best towing trailers on the planet!
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BenK
SF BayArea
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Joined: 04/18/2002
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Hope you are beginning to see that things are not absolute nor one
size fits all. Meaning if the MTWR is listed at 5,000 lbs, does it mean
in all conditions/cases/situations/etc is the rating 5,000 lbs. It depends
on other attributes or variables. Ditto one size fits all, as that is
a form of absolutism.
Every thing has a food chain and has a weak link in regards to strength
and ratings. Not understanding that will have this type of discussion
useless and go nowhere.
In the food chain of towing there is a receiver, which is the component
bolted to the TV to hook up the trailer.
There are 5 classes (Class I, II, III, IV, V). Look them up either here
or on the Internet.
Here are two pictures of one from a GMC 9,200 lb GVWR (light 1 ton,
or heavy 3/4 ton) and my GMC 8,600 lb GVWR.
Notice that there are two ratings for each. First is for weight carrying,
which is without WD (weight distribution...transfering weight from
the rear of the TV to the front of the TV). Other is with a WD setup.
There are thousands of pounds of forces on the WD system, which includes
the TV itself.
Then an understanding of and the differences between static and dynamic
loading or forces is a must.
On that, the understanding of the differences and construction between
a Monocoque (Unibody) and ladder frame is a minimum. Without that understanding
(both strengths and weaknesses), this discussion wont' go far.
Most all ladder frame vehicles has a monocoque body sitting on it via
isolation dough-nuts.
Monocoque is generally best for 'cars', not for heavy loads. Not to say
they can't...the current designs are just not designed for heavy loads.
Anyone ever ride in a high mileage taxi? Rattles and squeaks, right?
The wonderfulness of a solid (no movement between sheetmetal panels,
therefore no rattles/squeaks/etc of older designs...ladder frame)
monocoque is lost once a 'single' spot weld fails. Failure is not completely
coming apart, but when stress fractures appear around it to allow
movement, ever so slight movement....which will propagate into larger
movement, which will propagate into another spot weld failing...
One can design a monocoque that will be great for towing heavy, but
the gauge of sheetmetal will become both cost and weight prohibitive.
Also increase the pitch of the spot welds...meaning more spot welds
per foot of seam. Again cost becomes an issue. Best yet would be a
continuous seam weld, but that would be the most costly for this type
of architecture.
VW/Porsche has gone thicker and higher pitch monocoque on their SUV.
Jeep has a monocoque with a mini frame welded all along the underbelly
or pan. Ditto the Ridgeline, it has a mini frame welded on the
monocoque. Has the rigidity of a monocoque and the stoutness of a
ladder frame, which is limited to the gauge and box section of that
ladder frame. Just look at it's actual weight vs size and the cost of
those things....and their MPG vs comparable sized TVs.
This is just a very short dissertation on 'some' of the stuff involved
with the design, manufacturing and use of a monocoque vs ladder frame
architecture.
So back to your question. It depends on the receiver and the body
panels of your monocoque TV. The OEM has better knowledge of the system
and component limits.
On that, I'll also argue that they screw up royally all to often, but
generally, on these things, I go by the OEM's numbers.
One limiting factor is the receiver rating and there should be a label
like the ones I've posted. An example would be a mythical 2,000 lb
trailer with a 1,000 lb tongue. On my receiver, it would be over the
500 lb dead weight rating and must use a WD hitch system.
Another is the fact that you say the OEM does not recommend a WD
system. Sure many have and will use a WD system and no 'apparent'
problems, yet...
Again, bottom line is a risk management decision and I always say to
ask yourself who will pay if a warranty position is needed. Will the
folks who recommend 'sure you can'? If the dealer/OEM, then you are
on their turf and their ratings/specifications.
-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...
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GBlack
Evansville, Indiana
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Joined: 08/10/2006
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Thanks all, for the info! That makes sense, smkettner, about the focused weight on the tongue versus the entire payload weight being spread out.
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BenK
SF BayArea
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Joined: 04/18/2002
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GBlack wrote:Thanks all, for the info! That makes sense, smkettner, about the focused weight on the tongue versus the entire payload weight being spread out.
A ladder frame will have the load/forces spread out over it's whole
length and is designed for it. The body (monocoque/unibody) does not
see this load/force.
A monocoque (unibody) will have the load/forces on the panels the
receiver is bolted to. It then needs to spread that (distribute, as
in WD) to the rest of the body panels via the spot welds.
Think of a step ladder with a monocoque on it, say a humongo egg. The receiver
is bolted to the ladders two rails and the WD forces are imparted on
those rails to lift the rear end and transfer (distribute) the force/load
to the front via the ladder's rails. The egg sees none of that.
No a humongo egg made from pieces spot glued together and with a receiver
bolted to one of the rear pieces. The WD forces will be imparted on
that rear piece, which will then transfer (distribute) that load/forces
to the next piece via the spots of glue. Then to the next piece via
it's spots of glue and so on till it reaches the front where the
front axle ties into it.
If one spot of glue weakens, then it will allow a bit of movement.
Over time it will further weaken and then enough movement will weaken
the next spot glue...and so on and so on.
You can make a monocoque (unibody and OBTW, an egg is the perfect
representation) work by increasing the egg's shell thickness and/or
strength of material. Then you need to put the spots of glue closer
together and/or over lap more. Best yet would be to lay down a
contiguous seam of glue.
But then this humongous egg would become really heavy and expensive
to make.
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Road Ruler
Canada
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Joined: 09/11/2003
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BenK wrote:
Another is the fact that you say the OEM does not recommend a WD
system. Sure many have and will use a WD system and no 'apparent'
problems, yet...
Again, bottom line is a risk management decision and I always say to
ask yourself who will pay if a warranty position is needed. Will the
folks who recommend 'sure you can'? If the dealer/OEM, then you are
on their turf and their ratings/specifications.
Of all the multitude of Honda Ridgelines that are using WDH's we have never heard of an issue.
Compare that to the multitude of issues caused by the weak and problematic GM receivers. Good thing the GM receiver is covered under warranty!!!
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Caddywhompus
Southeast WI
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Joined: 06/27/2001
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The posts stating unibody vehicles can't use WD hitches are grossly out of date with the times.
I've been using WD hitches on the last 3 unibody vehicles, and that's a span of about 10 years and maybe 50k miles towing. Properly setup, they work EXACTLY the same as ladder frame vehicles, often better. Without my WD hitch, our minivan would be limited to 350 pounds of tongue weight, which would sag the rear of the van significantly. With the WD hitch, I can run with up to 550 pounds of tongue weight, evenly distributed front to back. The van stays dead-level and handling is as good as without the trailer. You could expect the same results from the Highlander.
Better? Yes Better. Ladder frames flex, which is why pickup trucks have separate cab and bed parts. When the WD bars are tensioned up, sometimes the frame flex absorbs some of the twist BEFORE weight starts to transfer. Unibody vehicles are often built so rigidly that they DO NOT FLEX as much as ladder framed equivalents. Less flex means the WD hitch works BETTER.
'04 Ford Freestar (Primary tow vehicle)
'05 Subaru Forester (Backup tow vehicle)
'65 Bethany popup (best popups ever made!)
Looking for a tow vehicle
Minivan towing
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