Oops, forgot to ask another thing. Is there a general rule as to WHEN weight distrib. hitches (WDH) are needed (e.g., if tongue weight exceeds a certain amount)? Or does one simply look at the rear end of the tow vehicle to see if it is sagging, and judge based on that? Also, are air bags an alternative to using a WDH, or do they serve a different purpose?
Thanks again for helping me make an informed decision,
Gary
WDH's should be used if too much weight gets taken off the front axel from a steerage point of view. Some rigs taking 100 lbs off the FA will cause enough of an issue that you will want some kind of WD setup. Others like 8lug 25 and 35 series trucks, you will not notice it until you hit about 300 lbs. This will usually be in the 1000+ lb HW or there abouts. A rig like you Toyota, it may be 300-400 lbs. of HW will take off enough to have issues.
On my old truck, my TT with 650-700 lbs of actual HW took off 60-100 lbs off the FA. Not noticable. I did use a WD system, more because it did not get side to side movement in crosswinds vs no WD at all. A dual cam I put on later made it that much easier to tow yet. "IF" you can put on some kind of WD or equal, you will notice the difference in towing, even if it truly is not needed!
My equipment trailer with 1500 lbs of HW took off 300 lbs on the FA. This was noticable on wet roads. Meanwhile, the ET takes off 60 lbs off my Navistar dump truck. I do not notice this either. My dually has about 200 lbs off the FA, for the most part, not noticable.
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
3 Single axle utility trailers
Marty's advice is very good, but pertains more to RWD vehicles than FWD ones like a Highlander.
With FWD, you want to keep the front tires properly weighted for all the reasons Marty mentioned, but also because you'll need the traction on slippery surfaces. Without the WD on my minivan, the front tires will spin easily on damp pavement, grass and gravel. With the WD, none of this happens.
Now I realize the Highlander is technically AWD, but a better definition would be "Front Wheel Drive with the ability to engage the rear axle on a limited basis when the front tires slip". So the application is best handled by treating is like a FWD vehicle.
And to answer your question about how much tongue weight you can carry without WD? Well that's fuzzy. First of all, to put 500 pounds on your hitch without WD is going to be a wake up call. I don't care what Toyota says, 500 pounds on the ball is GOING to sag the rear of the Toyota and create handling and traction problems. Going lighter from there, you could probably get away from the WD hitch with less than 300 pounds of tongue weight, but you may find you can't carry anything in the back of the vehicle without sagging even at this weight. And then, how often will you be doing this? If you plan to tow once or twice a year, you can probably deal with a little rear sag. If it's every weekend, then probably not.
I'll share my personal experience for you. Even though my tow vehicle is a minivan, the results would be surprisingly similar. I can carry 300 pounds of tongue weight without the WD, but the rear of the van sags almost 1-1/2". For short term trips, this isn't even a concern. But for long term driving, it sure is nice to correct it. With the WD installed, I can carry up to 500 pounds of tongue weight, plus have gear in the back of the van, and everything stays dead level. I started out with a light-duty WD hitch (mini-350), which helped a great deal at 300 pounds and under, but I found over 300 pounds it became ineffective. So I upgraded to a standard WD hitch with 550 pound bars and solved the problem. And YES, I had to install an aftermarket hitch to get the capability to use WD at all, since the factory hitch wasn't rated for it.
* This post was
edited 11/10/09 08:19am by Caddywhompus *
'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
Caddywhompus wrote: I know the recommendation from Toyota re Weight Distribution is based on the same baseless premise as the one Honda attaches to the Pilot.---
You disagree with the Toyota recommendation so you label it as "baseless". This is opinion and not fact.
Quote: ---I know that Reese sells a class III hitch with WC and WD ratings specific for this vehicle. And I know that if it wasn't safe to install and use said hitch, Reese wouldn't sell it. Further, I know that when a hitch manufacturer designs a vehicle-specific hitch, it's mounting to the vehicle and structural integrity are both included in the ratings assigned.---
The fact that Reese sells a WD-rated receiver for the Highlander does not prove it is prudent to use one. Reese also sells a 3500# Class III/IV receiver for the V4 KIA Sportage which has a rated towing capacity of 1500#.
Quote: ---Further, I know that when a hitch manufacturer designs a vehicle-specific hitch, it's mounting to the vehicle and structural integrity are both included in the ratings assigned.
How do you know that? Can you provide factual evidence of the testing which is done to verify the structural integrity of the mountings?
I'm not up on receivers for monocoque and will try to find time to look see. Mainly
to see if they increased the contact points (spread the loading) to other panel
sections.
Admit very skeptical, as it would have to be fairly large to reach past the rear
most panel.
Again, not saying *can't*, but weary knowing how a monocoque works. Yes it is
extremely rigid in reference to a ladder frame, but that is also it's problem
with the high stress of a WD hitch system. It can be made to, but I don't think
current monocoque vehicles are...with the exception of the VW/Porsche SUV/CUV
They won't instantly fail either, as it takes time to over work those spot welds.
Do a search on 'spot weld', 'failure' and learn how they fail. Wonderful for
rigidity, fast production, etc...but there are down sides. Like corrosion, even
if the sheetmetal is galvanized. There is burn off of the protective layer to
expose bare metal. Worse because it an over lap seam to trap and hold moisture.
This is just a tidbit, as there is a whole science to fastening methodology.
If you are going to keep it 2-3 years, you'll not see these failures. Maybe even
longer and dependent on how you drive, where you drive and how you load up the
WD Hitch system (of course how much of a load too). The down stream owners will
see these failures.
As for the FWD, yes think it smack on why the proper setup of any WD Hitch system
we all talk about over the years.
The transfer (distribution) of weight from the TV rear to the TV front axle
is more than just traction for front wheel drive, but similarly to keep the front
axle geometry for steering/handling/braking/etc. Now with FWD, just add that to
the matrix.
Not all after market OEMs has the resources to test and certify to the levels
a major OEM can and does. A good example is in looking at after market rear
conversion disc brakes. Found that one after market instruction sheet said to
pinch off the rear hose with vice grips while doing the conversion. This is to
manage gravity flow of the brake fluid. More than plain stupid, dangerous, as
that will ruin the brake hose.
-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?...
Does the highlanders owner's manual claim you need to remove the hitch and plug the holes when not towing like the Sienna and Rav4 owner's manual does?
They also have a very low max speed warning when towing, 55mph?
Based on a crude pic measuremnt, 500 lb on the rear of a highlander will releave the front axle of ~175lbs. Would that be ~ 7% reduction in tire traction for the front tires?
BenK wrote: ...Again, not saying *can't*, but weary knowing how a monocoque works. Yes it is
extremely rigid in reference to a ladder frame, but that is also it's problem
with the high stress of a WD hitch system. It can be made to, but I don't think
current monocoque vehicles are...with the exception of the VW/Porsche SUV/CUV...
If you are going to keep it 2-3 years, you'll not see these failures. Maybe even
longer and dependent on how you drive, where you drive and how you load up the
WD Hitch system (of course how much of a load too). The down stream owners will
see these failures...
Ben, My Freestar is coming up on 5 years old, and nearly 100k miles. The Astro van that preceded it was 9 years old when we traded it in and had 90k miles, and the Plymouth Voyager that preceded the Astro was 20 years old when it finally went to the scrap yard, and had a whopping 290k miles at junk time.
All 3 of these vehicles are unibody in design. All three of them had aftermarket class III/IV hitches (1 Reese, 1 Curt, and 1 Hidden Hitch) and all 3 of them were used for towing trailer WITH Weight Distributing hitches involved. Not a single one of them fell apart on the freeway, even the Voyager which had a lot of rust at the end. All doors and windows continued to work, and the hitches NEVER loosened or tore free from the "thin sheetmetal" unibody. I'm not alone here, tens of thousands of other people are driving unibody vehicles with WD in place right now, as we speak. Andy Thompson has setup a few thousand all by himself!
To answer the questions about hitch design, first you have to accept a couple facts.
The "Thin sheetmetal" that you believe all these vehicle are built out of is actually high-strength steel, and is a lot thicker (at least under the vehicle) than you realize.
A lot of modern unibody vehicle actually HAVE a ladder frame underneath them, but it's welded to the floorpan (no body mounts) for increased strength and rigidity. (This is the confusion with Astro vans, since a quick glance underneath will show a frame, but you'd have to look closer to notice it's welded to the floor pan of the van. My other minivans were all built the same.)
The hitch manufacturer has to (by law) include the hitch's mounting points and attachment hardware in the rating of the unit to get DOT approval on the design. So yes, on a typical class III hitch designed for a unibody vehicle, the forward mounting tabs are located FAR forward up the chassis to counteract the stress of the spring bar tension. Backer plates are always included to place under the fasteners (1/4" steel stock) inside the chassis to prevent the bolt head from pulling thru the metal and further spread out stress.
And the last thing to point out is that these vehicles are generally-speaking "light-duty" tow vehicles. Meaning, under 5000 pounds tow rating in most cases. Therefore the stress and load of towing is LESS than the typical HD pickup owner, who might be pulling 13k pounds with a 1500 pound tongue weight. So the hardware does not need to be quite so over-engineered to perform satisfactorily.
It has become SO COMMON to use light-duty WD hitches on minivans, X-over SUVs and other light unibody vehicles that you can buy aftermarket hitches for them from any number of sources. In fact, the newer Chrysler minivans come from the factory with a Class III/IV hitch now (with HD towing package) that is rated at 350/3500 WC and 400/3500 WD.
Caddywhompus wrote: The hitch manufacturer has to (by law) include the hitch's mounting points and attachment hardware in the rating of the unit to get DOT approval on the design.---
Since you claim this to be a fact, can you provide a link to a DOT document which spells out this legal requirement?
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