Load leveling T&C shocks ?

Surely -- air shocks. They can be inflated from any tire pump.

No. No. No.

Never use the shocks, air or otherwise, to level a vehicle in this situation. "Nivomats" are a system -- not just shocks.

Standard shocks aren't meant to carry the weight of the vehicle, they're intended to dampen suspension movement. Their mounting points were never intended for this purpose. It's a really *bad* idea to raise a vehicle with air shocks. This idea was commonly employed in the 70s and 80s when the 'raised rear' look was popular on RWD vehicles. It resulted in a lot of broken shock mounts and broken shocks. Some were more successful than others, to be certain. Those folks are known as 'lucky'.

If the van sags dramatically under the tongue weight of the trailer, it's overloaded, plain and simple. You're asking too much of it. If on the other hand, it merely rides a bit lower, than determine the tongue weight of the trailer, and compare this value to the published maximum trailer tongue weight rating for the vehicle. If the actual tongue weight is "within spec" -- then the sag needs no further attention. Don't alter the vehicle.

The springs are supposed to carry the weight of the vehicle, and suspend it at ride height. I would recommend against changing your vehicle -- a vehicle's suspension, braking and handling dynamics are the product of a *system* that's designed to work with components of known properties. That said, the proper way to raise the ride height is to increase the spring rate in the rear. This can be accomplished in a variety of ways -- changing the springs, adding 'helper springs', adding air bag suspension 'helpers', etc. If you go this route, you will undoubtedly be adversely affecting your brake proportioning, which can be a deadly serious issue when towing a load (think about the words 'jackknife' and 'brake failure').

The words "heavily loaded and trailer attached" combined with "'03 T&C" worry me, quite frankly. For occasional, light duty towing, a T&C is adequate. For packing the family up and towing a camping trailer, it ain't up to the job, and could be hazardous to you, your family, and anybody else on the road.

/soapbox mode off

--Geoff

Note that he's not proposing Nivomats.

I've heard this claim before, but never quite understood it. The problem is, the loads that the shocks transmit to their mount points are greater than the ones the springs transmit: while the springs are transmitting the weight of the vehicle as you point out, it's the shocks that are transmitting all the high-amplitude transients. So it would seem like the shock mounts would have to be at least as strong as the spring mounts. Also, of course, the factory load-levelling system in the '70s used air shocks (at least, on my Newport).

Here you've got an undoubtedly valid point.

Er...OK. I'll take your word for it, though I've certainly seen it done often enough to have concluded it was a standard and acceptable practice. Perhaps as you say those who got away with it were just lucky, or perhaps the ability to do this (regardless of official sanction) was contingent upon overly-engineered shock mounts that are no longer commonly found.

...except to aim the headlamps downward so they're not pointing up in the sky (and other drivers' eyes).

Now, this is overstating the case rather severely. People have been successfully installing different springs, different shocks, etc. for

*years*. As long as the components are thoughtfully selected, there's seldom a problem and often an improvement.

C'mon, now you're *really* laying it on thickly.

Me too, if for no other reason than the ability of the transaxle to withstand such service.

Because its bogus.

I love it when reality intrudes on silly statements :-)

My '73 Satellite manual mentions both dealer-installed air-shocks and dealer-installed coil-over load levellers. All of the big-3 had similar "towing packages" with coil-overs or leveller. In fact my car has run most of its 400,000 miles with coil-overs since it used to do trailer towing duty and still gets called on to act like a pickup truck sometimes. I can truthfully say that my Satellite is slower with a 440 in it than just a 318... of course the 440 (bare block) was riding in the trunk on the way to the machine shop :-)

Steve, I'll defer to your greater engineering knowledge 'most every time. I do know what I've been taught, but sometimes the actual physics behind it is a bit murky.

That said, why not just use air shocks to suspend the vehicle? Why use leafs or coils at all? (My guess: it's too much to ask of a shock absorber to both suspend *and* dampen suspension movement. But it's a guess. I know that I've seen many air shocks bent nearly in half.)

(Notwithstanding Lincoln's air bag suspensions, which can frequently be seen in complete failure around here.)

Again, a guess: in the typical situation, the transient load is shared between the springs and shocks. Perhaps raising a vehicle with the shock absorbers affects the amount of the load that is shared, placing a much larger proportion on the shock absorber mounting points. And remember, we're talking about a minivan, not a Satellite, which may well have been engineered with the idea that the load on the shock absorbers could increase dramatically beyond normal in towing situations.

--Geoff

Yes!

I believe the key words here are 'thoughtfully selected'. I question the extent to which this is possible, but I'll agree that you make a good point.

There's tolerance in every design for foreseeable abuse, as I understand it. Start changing the design significantly, and it's easy to imagine secondary and tertiary effects that aren't easily predicted.

Perhaps the OP is a mechanical engineer. Maybe he's been professionally installing trailer hitches for half a lifetime. I dunno. My own father-in-law drove a pickup truck for years with 1-ton overload springs installed on his half-ton Chevy pickup, and used it to tow a

10,000 pound camper all over hell's half-acre. With a homebrew drivetrain, to boot. I wouldn't describe him as an engineer, or even particularly well educated, for that matter. It worked...but I'll be damned if I'd call it a safe design. Thankfully, he apparently never got into a serious accident-avoidance situation.

Another relative...another camper, this time being pulled behind a half-ton Chevy G-series van. Came over the hill doing about 45MPH, discovered that a.) the road curved and b.) had a stopsign about 200 yards away from the crest. One thing lead to another, the remote control for the trailer brakes was out of reach, and before she knew what was happening, the thing was sideways, then ass-over-teakettle. Destroyed the van, the camper, and nearly killed everyone inside the van. The van was overloaded, the trailer brakes were thought to be adequate compensation. They weren't.

I take the towing safety stuff seriously as a result.

--Geoff

I will 100% agree that in a conventional spring/shock combination, the shock mount points should not REPLACE the springs. But adding a set of

300-lb "load levellers" is very different than suspending the whole back half of the car on the shock mount points. And I never said that it wasn't stupid to "jack up" a car with air shocks. Again, that is very different than simply levelling a load with them.

Yep.

I can't speak directly to minivans, never having owned one. But I

*thought* that load-levelling shocks were still a factory option with them. If not, then I wouldn't try it for exactly the reason you mention.

Dang it Stern, Shock absorbers are just that, shock absorbers. LOL

If you have a trailer towing package your rear leafs or coils are going to be designed for increased load. Incrementally heavier loads. that is why the arcs of the springs are different.

If you overwhelm the stock springs with too much load then your vehicle is not going to be suddenly "all better" when you add air-shocks. If anything your vehicles rear end will bounce around due to the lack of shock absorbtion if you install air shocks.

Joe P. wuz correct - shock mounts are NOT meant to bear the weight and forces induced by loads. That is because SHOCK are not meant to bear the weight - only to reduce rebound and harmonic bounce.

Airshocks never were designed for anything less than trouble. BECAUSE - they are solving the symptom and NOT the cause.

The only way to fix heavy hitch problems are to reduce or reload (redistribute the load) of your trailer so tongue weight is not exceeding capacity or to respring your vehicle to accomodate heavier hitch weights.

To correct vehicle level problems you have to install a airbag system ot other adjustable system such as that used in the newer Lincoln Navigators, (self leveling)

Zork asked for a simple fix for a problem that is not easily fixable unless he was within capacity, and can learn to live with high beam flashes..

Actually, no. They're nothing of the sort. They are oscillation dampers. The term "shock absorber" is quite a misnomer.

Assuming you mean me, there was a mis-attribution somewhere (and my server seems to have missed a good part of this thread). What I said was that I've never understood that claim: since the shocks have to handle the high-force transients, I would expect their mounts to be *at*

*least* as sturdy as the spring mounts. I also pointed out that the factory load-leveller system of the 1970s (in particular, the one on my Newport) used air shocks.

Misnomer...loll...

OKAY, then redefining is what you want?

They (Shocks) are either or both of Shock absorbers or Oscillation dampers. They are STILL NOT SPRINGS or LOAD-BEARING devices.

Therefore...

Install or order springs for the load and shocks for the bounce.

DO NOT ORDER AIR-SHOCKS to counter improper loading of trailer. ( as you had so casually suggested )

I'd call them motion dampers. The motion doesn't have to be oscillatory in nature.

Matt

I much prefer the more technical term "bump stopping thingies".

Geez - you'd think a complex formula could be summed up in an approximate two-word name for something!! At least my attempt uses three words - 1/3 again as much ability to define complex equations.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

There has been no mention of the "Torsion Bars" being used on the trailer. These must be adjusted to the proper level.

Another point is, We would never pull a trailer heavier than the tow vehicle. Bob