RE: [A/S] Pulling an Airstream trailer with ML 350

["Oliver Filippi" <ofilippi@xxxxxxxxxxxx>]

The laws of physics are against you.

I discussed this topic with a Mercedes factory rep at a 2006 introduction of
the new ML (but the logic is still essentially the same - though the new one
(I believe) is built on a frame rather than a unit body, which is better
adapted to a weight equalizing hitch).

He indicated that the towing capability is essentially for hauling a boat to
the local launching ramp or marina.  The ML is not intended to be a heavy
duty tow vehicle for extended trips with a travel trailer.

Note that an auto manufacturer's towing capacity has many definitions.  In
this case, (in my opinion) it is the safe(?)load a trailer can put on the
chassis, drive train, and tires without breaking.  BUT NOT how practical or
safe the vehicle would be on the highway (say in a cross wind), or how well
it would perform from a power standpoint.

As has been pointed out, the wheelbase is relatively short (which would
limit your trailer length).  On the other hand, the Mercedes suspension is
better than most, has a low roll center, and typically has big fat tires.
Thus you can safely stretch the tow vehicle wheelbase guidelines a BIT.


[Some thoughts about desirable tow vehicle wheelbase.

Clearly a longer wheelbase on the tow vehicle will increase the stability of
the entire rig at speed on the highway.  However, tow vehicle wheelbase is
ONLY ONE factor in the equation.  Tow vehicle weight, suspension design,
roll height, and tires and wheels all contribute to tow vehicle towing
performance - as does the hitch and sway control.  I towed a '76 Tradewind
(25' but over 1000 pounds lighter than current versions) with a '74 Chevy
Blazer for many years. (In those days, for those who may not remember, a
Blazer was a two door, 1/2 ton truck on a shortened version of the half ton
pickup chassis.) I never had a problem with the "tail wagging the dog", but
note that a 25' Airstream does not have a long rear overhang (past the
axles).  Also, I installed a rear sway bar and larger Michelin truck tires
(on wider rims) and used a dual cam Reese hitch and an E-Z Lift friction
sway control - the best I could find then.  Thus, my Blazer was a bit more
capable than the stock variety.  The big plus was maneuverability. It was
easy to park the trailer, even in difficult to access camp sites, etc. (I do
miss this maneuverability with my current (longer wheelbase) extended cab,
short bed, 4WD, 3/4 ton Silverado pickup.)  On the other hand, the new
Silverado is a FAR SUPERIOR tow vehicle. The modern computer controlled 6
liter engine and transmission is remarkably competent - though I did replace
the Flintstone - er Firestone tires which came with it for a set of
Michelins. The new tires made a noticeable difference.] I sill use the same
Reese hitch system, reconfigured to the new receiver height.]


The ML does have a two speed transfer case and all wheel drive.  Thus, it
could pull a heavy load even on less than great surfaces, or get it out of
an awkward situation.

The bigger problem, in my opinion is the small engine (though you could drop
a fortune and get the AMG model with still bigger tires and a 5 liter
engine).  The 350 (3.5 liters)engine is really too small, even if it can
develop the necessary horsepower.  You ought to have a 5 or 6 liter engine
in order to have adequate torque (which gives you the necessary acceleration
capability).  Small displacement engines get their power by running at
higher RPMs.  Towing with this sort of drive train means that you will be
constantly flooring the accelerator pedal and using lower gears.  The engine
will be screaming much of the time.  This is not a formula for reliability
or longevity - even if it is a Mercedes.

Oliver Filippi