Hitch capacity, springs, airbags, etc. [split thread]

Seems to me that the air bags are mainly a "helper spring" and would indeed cause less wear on your leaf springs. Not your axle though.

[Mr. Adventure]

Except that leaf spring wear is not a problem you reasonably expect to ever have.

[Wavery]

Originally Posted by Mr. Adventure

Except that leaf spring wear is not a problem you reasonably expect to ever have.

Not necessarily so........ This town is full of leaf spring shops.

It's actually more common than one might think. People tend to overload the back of their trucks on occasion. This is very hard on leaf springs. Leaf springs, sometimes, even break in half.

Air bags help tremendously in sharing the load.

[Mr. Adventure]

OK, I defer to your experience.

Overloading springs doesn't sound good to me, because bottoming out has to create big loads at the axle. You've see broken pickup truck axles?

I was really impressed by mtnguy's weight numbers showing that his 480# tongue put 700# on the rear axle of his pickup without the WDH.

[Brutus]

I can say I've beaten on my leaf springs before. Putting a pop-up slide-in camper in the bed of a '97 F150 will cause the bed to sag down to the bumper stops and just-about straighten out the stock leaf springs. With family in the truck, I was definitely over the payload limit. I put a set of Timbren overloads over the rear axle. Basically they're just a pair of solid rubber bushings that sit on over the axle, but off the bed when empty (so the suspension can soak up bumps when empty). As you load the bed, it sags down until the bed sits on the Timbrens. Kept the vehicle level and saved the suspension. Not having the low beams illuminate the night sky was an added bonus. Tires could easily handle the slightly extra load. Not sure about the axle, but never had any issues with it.

[T and C]

It's probably OK to have the airbags, given that they were made by someone who thought about these things. But you're potentially exceeding your rated rear axle capacity and you would be violating your manufacturer's warranty if you did that.

Ratings are guidelines, and I share your lack of concern about a can of beans. But a weight distributing hitch keeps the trailer tongue weight from unloading the front wheels, which air bags can't do. So, you're still reducing the weight on your front wheels where most of your braking and all of your steering happens.

Regardless, you've taken quite a leap from that lofty "erring on the side of caution" perch you were posting from earlier in this thread.

Mr. Adventure,

First off, let me say that if my comments about towing with medium weight vehicles were offensive, I heartily apologize. I had no intention of "dissing" you or your Highlander.

I am not very worried about exceeding my axle weight. Here is why:

My model of F150 is available with five different "payload packages". Each one increases the payload by providing heavier spring support for the rear of the truck. There is a corresponding increase in the GVWR of the truck.

My truck has the 1680# payload package with a GVWR of 6900#. One can also order an 1870 payload package with a GVWR of 7350. All of these trucks (2X4) have the same axle!

Notice that on the same axle I have one can carry up to 190# more payload and have a GVWR that is 450# higher. But...still on the same axle. I could be wrong, but it looks to me that that axle is stronger than they are letting on.

If this is the case, I am nowhere near the limits on my axle with a 500# tongue weight. Plus, you just know that Ford has a liberal built in reserve factor in those numbers. Toyota undoubtedly has them as well. So I think that can of soup will damage neither my hitch nor my axle.

I am leaving on a trip Tuesday. If turn out to be wrong I will 'fess up upon my return.

One other thing: Regarding the unloading of the front axle. Do you mean to say that my front wheels are supposed to touch the ground ALL the time? Not just when I am braking?

Seriously, my truck weighs in at 5100# on a 145" wheelbase. The weight and length serve to lessen the unloading effect of hitch loads. So, I am not very worried about that issue.

Tom
__________________

Originally Posted by T and C

Mtnguy,

I puzzled over your post for a while. Then I went to a Ford F150 site and read that many owners have replaced their class III hitches with class IV hitches at a cost of about $300.

Then I went to bed.

When I awakened this morning it was obvious to me that my subconcious mind had worked on the problem while I slept. The answer just surfaced in my thoughts as I awakened.

Look at those numbers again. We have been thinking that the 500/5000 limit had to do with the shear strength of the bolts that attach the hitch to the truck. BUT...look at that 990/9900 figure. If you load the hitch at 501 pounds it will fall off? But if you put a WDH on it will bear 990 pounds with no problem???

The answer is that both ideas are wrong. What Ford is regulating here, (to avoid liability), is SWAY. 500 and 990 are both exactly 10% of the weight limit they recommend. As we all know, the standard figure for the RV industry at large is that tongue weight should be limited to 10-15% of trailer weight.

But...TM's do not fit the average. Their axle configuration and low wind resistance both serve to limit sway beyond the normal limits.

So, I am not going to sweat the 500# limit too much.

Now if I throw an extra can of beans in the trailer and then the hitch falls off, I'm wrong.

Tom

I too can sometimes go to bed and solve problems....but I have to stay awake to do it.

Of course putting 501 lbs. on the hitch is not going to make it fall of. It can probably support the whole enchilada of 990 lbs. sitting in the driveway, but maybe not the continuous stress of going down the road with that kinda of weight. Using a WDH puts an upward force on the hitch, where the hitch is not carrying the full 990 lbs.....only a part of that.

I don't know if I agree that the 500 lb. tongue weight limit is for sway problems, unless you are considering the possible sway of the TV because of the messed up geometry of the truck by putting too much weight on the rear axle and taking weight off of the front axle.

I also have read of travel trailer owners replacing their Class III/IV hitches with true Class IV hitches. I pull a fairly lightweight conventional trailer (~5500 lbs. loaded), but if I were pulling somewhere close to the maximum with my truck I would consider a heavier hitch.....or a heavier truck. 1 problem with replacing the hitch on a F150, is that is a specialty product.......the bumper is actually attached to the hitch instead of the frame.

In regards to the comments about airbags and leaf springs...
I installed a set of Timbrens on the rear of my Astro a couple of years ago and very much like what they do.
Basically they are not airbags, but a "rubber cushion" that acts as a helper spring.
They don't do anything when the van is unloaded, only taking effect once load sags the back of the truck to make contact.
For us, this means that my wife enjoys a natural ride to work with an empty van, but on the weekend when my son and I take off for a rugby tournament with tons of gear and a few 200 lb buddies, the Timbrens kick in and work great.
I highly recommend these, as long as you understand what they do and know their limitations.

They attached in a way that transmits the load from the axle, directly to the frame, thus reducing the weight seen by the leaf springs when the van is loaded.

[Mr. Adventure]

This thread's gone on awhile now, well past the point where we stopped talking about helping somebody choose a Traverse for towing. But as always, I learn a lot when we wander off into truck talk:

- There's no problem loading a pickup until the springs bottom as long as you pad them a lot so that they don't break so much.
- A 7% or so loss of steering/braking caused by 200+ pounds coming off the front axle of a 150" wheelbase vehicle without a WDH just can’t be important, since it only happens when you're towing.*


*Mtnguy’s numbers showed us that his 480# tongue added 700# to the rear axle and took 220# off the front wheels without a WDH (by my calculations, you could make this up pretty well by driving a couple of mph slower, but that’s another subject). In my vehicle the no-WDH penalty is much more severe, of course, but the silver lining for me is that instead of subtracting weight, the WDH actually adds 100# up front when hitched. Mtnguy’s numbers: http://www.trailmanorowners.com/foru...ead.php?t=7041

[Brutus]

Soooooooo Ken (the OP), is DW good with the Traverse or have other tow vehicles entered the mix since your last post?

If I were going the SUV route, a 5200# tow-rated Traverse would definitely be a contender, especially now that GM vehicles have a 5 yr / 100k mile powertrain warranty.