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Bryan
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Polite but inconsistent!
Here are some Toyota e-mail responses in regard to 45 mph speed limit.
I apologize for your concern regarding the towing speed specification for your 2008 RAV4 and 2006 Sienna.
You can go by the text in the Owner's Manual, which shows the correct maximum speed for towing, which is Toyota's recommendation for your vehicles, for safety.
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we appreciate your inquiry on the recommended towing speed in the Owner's Manual for your 2007 Sienna.
Our caution in the Owner's Manual is only a recommendation as we want our customers to be safe when they are towing.
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Ford's owner's manual towing limit
1998 Ford F150.
"Do not drive faster than 88 km/h (55 mph) when towing a trailer."
2009 F150 manual.
"To ensure proper “break-in” of powertrain components during the first 500 miles (800 km) of trailer towing, drive no faster than 70 mph (113 km/h) with no full throttle starts."
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BenK
SF BayArea
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Joined: 04/18/2002
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If truly trying to reconcile this, then get an 'expert' (ME...mechanical engineer)
and if still doubters, a PE (professional engineer, certified and licensed by
the state) to review and comment.
They won't do it without being paid.
I'm not an ME, nor PE, just someone interested in anything automotive and mechanical.
Have designed & managed the design of many things and have my opinions/comments
posted on your other threads.
The above letter from Toyota restates all that I've been posting in
your other associated threads here.
If you are truly trying to reconcile this, then educate yourself on what a ladder
frame and mononcoque (unibody) is. Look up 'unibody' and you'll find that it
references monocoque. Then note that in automotive bodies, the unibody does NOT
carry the load, but the chassis does.
These are the 'classic' definitions and in reality, it is really a kinda sorta
all and not in one.
The chassis or platform is the pan that the body is spot welded to on a unibody.
That is like a 'L' laid on it back and the upright leg is the firewall, as
the 'chassis', or 'platform'.
The 'box' section of this chassis/platform is small and that is where the body
comes in. It is spot welded to that chassis/platform to increase the box section
The various component/systems then hang on this 'known' platform
or building block. Why they can turn a Camry into a CUV, or a Carola
into a RAV4, or a Civic into a CRV, etc. They are NOT SUVs because
they are derived from 'cars', while true SUVs are derived from ladder
framed trucks.
That chassis with a different body spot welded onto it...
Touch on how a WD Hitch system works in a very simplistic manner.
Think of hooking up your TV and trailer with a WD Hitch system, but instead
of the WD bars, stuff a length of 2x2x36 inch steel bar stock into the TV receiver.
Stand on the trailer tongue and then lift up on the end of that bar. That is
what a WD Hitch system basically does.
Some of the weight will be transfered back onto the trailer tongue, as you
are standing on it.
The TV rear end will lift to remove some of the weight. How much depends on how
hard you lift up, or are capable of.
The TV front end will then have some weight moved from it's rear to it (weight
distribution...aka...WD).
Then think of how that weight is distributed. The food chain is through the
TV body or frame.
If ladder frame, the body does NOT see any of that.
If unibody, the chassis and body does see it. Mainly the chassis, but today's
unibody designs use the body as part of the box section and food chain.
The various sheetmetal panels are all held together to each other by overlaping
seams that are spot welded together.
Now jump up and down all the while holding up that bar.
That is what, simplistically, the WD Hitch systems sees while you are driving.
Then imagine each sheetmetal panel being compressed and then tensioned (stretched).
That the seams and spot welds see compression and then tension.
Since spot welds do not move, something has to give and it its the sheetmetal
around those spot welds.
Over time one of those spot welds will fail from the micro fractures that will
develop around it.
Now, back on your reconciliation. Am amazed you got that letter from Toyota
and congratulations for that.
Then consider the fact that you are asking a technical question and a technical
person should answer it....but....you will usually never get an engineer to
do that. It will come from someone in marketing, customer service, or legal.
None of them will be an engineer, and if so, they left that to become a marketing/sale/legal
person.
This *IS* rocket science like stuff, as that is what rocket scientists
do, design according to the laws of physics, just like any automotive
designer...just one has much more power and complexity.
Why at the beginning, suggested you filter this through a ME/PE.
-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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Well, I officially give up trying to get an accurate, clear and honest answer from Toyota USA on the WDH. Despite their initial reply that it's OK to use a WDH, the guy has changed his recommendation after I forwarded him an email from Toyota Canada (forwarded to me by guy on ToyotaNation.com who also owns a Highlander) saying a WDH is NOT recommended for the 2009 Highlander. Although my contact at Toyota USA claims he just made an “error”, I feel he may have arbitrarily tossed out a recommendation hoping he wouldn’t be called on it. After being questioned, I feel he changed his recommendation to NOT USE WDH due to that other email and/or the lack of test data since Toyota never tested their hitch using a WDH (because they claim a WDH isn’t necessary under 500 lb of tongue weight).
Although I like my Highlander, this nightmare of trying to get accurate, clear and honest technical info from Toyota has caused me to never want to buy another Toyota again.
The most recent succession of emails is too long to post here. But if you are interested in seeing them, PM me your email address and I’ll forward them to you. They consist of another three back-and-forth emails between each of us, ending in my statement that I’ll never buy another Toyota again.
Although I have a sore head from banging it against the wall 20 times, I’m still considering a WDH! At least that’s what the hitch shops and my internet friends here tell me I’ll need for tongue weights over 300-400 lbs. Obviously Toyota and their dealership service depts. don’t have a clue.
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Caddywhompus
Southeast WI
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Joined: 06/27/2001
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As I mentioned earlier, a WD hitch is the right equipment for your application, but I wouldn't use it with the OEM Toyota hitch. Reading through Toyota's responses and statements, it is becoming more clear to me that the OEM hitch itself is not designed for WD, and therefore Toyota is trying to turn people off to the idea of using one. They would never advocate you replace the hitch with one rated for your needs, so what else can they do?
He's another example of a similar situation. Several years ago I bought a '95 Astro van, and shortly thereafter a small 20' travel trailer. I had no idea what my specific van was rated to tow, even though I knew Astros on the whole had decent towing ability. So I emailed GM customer service and asked. After providing my VIN, they promptly informed me my van had a tow rating of 1500 pounds. I WAS SHOCKED, and it took me some time and a LOT of emails to understand this. Basically, my van was ordered from the factory without Chevy's OEM towing package. GM's policy on this is that any vehicle not equipped with their towing package is limited to class I towing forever. Even though they admitted that I could install all the towing equipment the van was missing (typically aftermarket stuff is better anyway), they won't stand behind stuff they didn't provide with the vehicle and therefore won't agree to an increased to rating.
So had I called Chevy, took their advice as unbreakable law from above, I would have had to sell my van and buy another at great expense. I chose the other route, where I installed the wiring, hitch and transmission cooler that was missing and towed happily until we sold the van 80k miles later.
So you can listen to Toyota's well-intentioned-but-pooorly-executed tripe about using the right towing equipment, or you can think for yourself and get the job done right. What you CAN'T DO, no matter how much Toyota and you might want it, it properly tow a 5000 pound travel trailer WITHOUT a WDH. You can't even tow a 3500 pound travel trailer properly while following Toyota's ruling, because the tongue weight is going to sag the Highlander so badly your headlights will be in everyone's eyes. There is only ONE WAY to do it right...
'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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DIYGuy
TX, NY and all points in between.
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Joined: 08/06/2005
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"Although I have a sore head from banging it against the wall 20 times, I’m still considering a WDH! At least that’s what the hitch shops and my internet friends here tell me I’ll need for tongue weights over 300-400 lbs. Obviously Toyota and their dealership service depts. don’t have a clue."
Help me understand why when looking for justification, the internet is more accurate than the manufacturer?
The manufacturer waffled, flip-flopped and eventually said not tested, don't know.
The internet and the guy trying to sell you a hitch says OK, and because you want to do it, then they must be right.
This dynamic is played out here almost daily on any number of threads where in the absence of black and white approval from a reliable source, the first one to agree with what we want to do is elevated to a position of authority, and those that don't agree are deprecated to enemy status.
For the most part, the internet is a collection of anectdotal tribal musings on life where we all want to be right and loved.
I'm sure there's a few thesis' in here on social acceptance vs. cultural polarization.
Bottom line is that in the absence of sound engineering analysis (read big $$$) it's at best an educated guess if you can make something work outside of it's design parameters.
A WDH on a Highlander falls into that category...
Full-Timers, Class of 2011
2002 Volvo VNL770 Toter - Optimus Prime
2007 SpaceCraft - Just Weight
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GBlack
Evansville, Indiana
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Joined: 08/10/2006
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Caddywhompus wrote:
So you can listen to Toyota's well-intentioned-but-pooorly-executed tripe about using the right towing equipment, or you can think for yourself and get the job done right. What you CAN'T DO, no matter how much Toyota and you might want it, it properly tow a 5000 pound travel trailer WITHOUT a WDH. You can't even tow a 3500 pound travel trailer properly while following Toyota's ruling, because the tongue weight is going to sag the Highlander so badly your headlights will be in everyone's eyes. There is only ONE WAY to do it right...
Thanks caddywampus. Having no TT or hitch experience, that's the type of practical advice I need.
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David_in_TX
Grand Prairie, Texas
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Joined: 11/27/2007
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The ratings are not to be brushed off as "guidelines", they are calculated by engineers, and you must never exceed them. I have posted about this in the past, and do not have the time to repost all of the facts again, so here are two threads to read:
http://www.trailerlife.com/cforum/index.........d/23158808/gotomsg/23165333.cfm#23165333
http://www.trailerlife.com/cforum/index.........d/23350433/gotomsg/23355216.cfm#23355216
BenK wrote:This isn't a perfect world, nor does one size fit all....
Ratings are not absolute, nor makes sense to us on the outside of the Product
Team which designed and certified the product.
Ratings is just a number decided on by the product team. It is the 'specification'
and again, not absolute. Meaning the wheels won't instantly fall off if you exceed
that number.
All of these ratings are based on the 'weakest link' and they all don't necessarily
add up.
For discussion purposes, I'll use my Suburban's numbers, as I know it best.
1996 GMC 3/4 ton Suburban, 4x4, automatic, highest/all options (including F60,
the snow plow prep package), big block, etc.
It weighs around 7,400 lbs with me (180), toolbox (+200), full fluids, and misc
stuff (about 50). Most others over at the Suburban forum with the
same setup weigh in at around 6,800-7,000 lbs (they don't have the
toolbox and misc I do). A far cry from the published curb.
Curb is listed 5,400 up to 6,000 lbs
GVWR is 8,600 lbs
GAWR, front is 4,250
GAWR, rear is 6,000
MTWR is 10,000
GCWR is 16,000
My rear axle is the exact same as the 1 ton dually of the same year. With the
brake cylinders the only difference I can find (mine are not as large in dia).
The supplier to GM is AAM and they rate this axle at 10,000 lb GAWR.
If I take the 7,400 + 10,000 MTWR = 17,400. Which is way more than the 16,000
GCWR. Then if I do load up to the 8,600 GVWR + 10,000 = 18,600...even more than
the 16,000 GCWR.
I'll not tow at my listed MTWR of 10,000 lbs. The real one is my actual TV weight
subtracted from 16,000 lbs. I then must watch the GVWR & rear GAWR, which
includes the trailer tongue weight.
Most folks think the numbers have to resolve exactly. They some times do, but
don't necessarily have to.
Bottom line is your own position on risk management...aka gambling. Gambling on
how your setup will perform on that bad day out there when you need to either
brake to avoid, swerve to avoid, etc. The heavier it is, the less performance
it will have.
The OEM has dialed in the vehicle to the min acceptable performance that is
mandated by DOT. Factored by the OEMs warranty requirements (longevity). This
is where there are large differences between domestic OEMs and even more so
with foreign OEMs.
Agree, your 4,600 lbs seems light to me. Go somewhere else and have it weighed
with the same loading.
Your math methodology is correct up to the point you questioned the result against
what you 'think' or 'want' it to be.
http://www.linkedin.com/in/davidnicholstx
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GBlack
Evansville, Indiana
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Joined: 08/10/2006
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DIYGuy wrote: Help me understand why when looking for justification, the internet is more accurate than the manufacturer?
Because speaking to folks on the internet with practical towing experience and (usually) no agenda is better than some young schmuck in the Toyota "Customer Service" who obviously has little knowledge of towing and is taking a strict CYA approach on behalf of Toyota. On the other hand, if I was able to speak directly to engineering design folks at Toyota, I would place much greater emphasis on what they told me.
I'm not looking for justification, approval, acceptance, etc. etc. I'm merely doing thorough research beforehand by asking folks who know because specific info from Toyota is not available (only CYA info). If I took everybody's stated CYA positions, I'd end up living my life in a cave.
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BenK
SF BayArea
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Joined: 04/18/2002
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I've been a designer/lead/manager/program manager/etc from industrial
controls, factory automation, process control, to computers and research
laboratories.
Been sued for wrongful death because my name was on everything
drawings, manuals, etc (designed by, drawn by, checked by, approved
by). Plus partner in some of these small controls companies.
Won every one and even counter sued. Insurance lawyers said my stuff
is what they dream of for a defense basis. My documentation from
design notes, to certification testing were all in line and was NOT
disclosed to the other side. Just portions and under NDA and closed the files.
I know what all of the ratings, signage, brochure, fine print, etc
all boils down to. When my equipment has signs saying 'dangerous
voltage', 'only trained and approved personal', they still went past the
locked gates, went past the locked and CB interlocked panel door,
etc are ignored. The court says my company did all they could and
not liable.
There were some wacky court cases where the judge/jury said that the
'old' stuff should be upgraded to 'current' standards. Why we got
out of the ski lift controls that year.
'Ratings' are what the OEM will stand behind and if you go over or past
whatever, you just bought the responsibility and took them off the hook
Repeat that they are guidelines to be followed. To not, then it is
a risk management decision (aka...gambling). Can't force folks to
follow the ratings.
Not to say the wheels will instantly fall off if you don't follow
the ratings...it just sooner and the biggies...performance will be
degraded and warranty will most likely be denied...if they find out
you don't follow their ratings.
Too many come to forums like this looking for the "sure you can" and/or
the "I've been doing it for decades/thousands of miles with no problems",
"you are good for it", etc. Bottom line, again, is that there is
only one person responsible for the setup and it is the driver.
Not the folks providing advice, nor will anyone providing advice
be liable, unless it is an official document from the OEM (and that
person has to be 'empowered' to do so, not the clerk who answers the
phone or email).
PS....living in a cave might be hazardous...dirt floors are not the
best living situation... 
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carringb
Corvallis, OR
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Joined: 07/28/2003
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Before deciding to ignore Toyota's printed recommendation, you may want to consider the warranty implications.
It's pretty clear that Toyota has not tested a WD hitch, and likely did not even account for it's loading when doing FEA on the monocoque (or any other chassis component). So... they don't know that it won't fail.
If there is a failure, they would be well within reason to deny warranty repair. And by fail I don't mean the car will split in half. More likely failures include floorpan deformation, squeaks and rattles, doors not closing securely etc.
Bryan
2000 Ford E350 DRW Wagon (14-pass all captains chairs)
V10 w/ Banks PowerPack, Diablo Predator, 4.56 LS, 250,000+ miles
Had: Weekend Warrior 41' FSW
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