RE: [A/S] Mercedes ML 500 and a 34 foot Airstream

["Oliver Filippi" <ofilippi@xxxxxxxxxxxx>]

Paul,

I don't think you will find the ML 500 to be a particularly good tow
vehicle, especially when you mate it to a 34' trailer.

I spoke to a Mercedes manufacturer's rep about six months ago at a Mercedes
"Test Drive Event" about using the ML to pull a travel trailer (in my case a
1976 25' Tradewind - which is a lot shorter than your 34 footer. Also, my
Tradewind is a lot lighter than today's 25 footers). His comment was that
the ML was NOT designed to tow a large travel trailer.  The towing capacity
of the ML was aimed more for towing a boat (on a trailer) from home to a
launching site.

From an engineering standpoint, the biggest shortcoming of the ML is its
short wheelbase.  Assuming the frame and drive train are strong enough, it
should be OK. But here too, I think you are possibly pushing your luck.  I
don't think the chassis has a lot of extra strength (safety factor) to deal
with the stresses and loads imposed by a substantial travel trailer for
extended periods of time.  Ditto, the engine and transmission.  Granted, it
does have a decent size (displacement) engine at 5 liters, though 6 liters
or more would be a lot better.  Modern Mercedes engines are of the high rpm
variety and tend to generate their power at higher rpm, whereas an ideal
towing engine would be one that develops its torque at lower revs. (If they
put a 5 liter diesel in the ML, it would likely be a much better towing
rig.) Also, I don't believe the ML's 5 Liter gas engine has variable valve
timing. (This design feature would allow even a high rpm engine to produce
strong torque at low rpm). If the engine does have variable valve timing, I
would be willing to give it a try.

The short wheelbase of the ML may not be as big a problem as it might be on
another vehicle since the ML's 4 wheel independent suspension (and front and
rear sway bars) will tend to keep all four tires on the ground for good
traction, and the fat tires and alloy wheels (less unsprung weight)will add
to that capability.  But be careful on slippery surfaces. Here too, the
Mercedes directional stability control feature will help to keep the tow
vehicle aimed in the right direction, well beyond the accepted short
wheelbase limits. But once the tires lose their grip (like hitting a very
sharp bump, a pothole, or hydroplaning on deep water) the fundamental laws
of momentum take over.

For many years, I towed my 25' Tradewind with a 70's vintage full size Chevy
Blazer (the only size they made then) and did not have any problems with
stability or sway. This included some pretty nasty rain storms on California
freeways and sizable cross winds. I used a Reese dual cam hitch with an E-Z
Lift friction sway control. However, I did install a rear sway bar and
larger, wider Michelin truck tires.  Today, when towing with a short
wheelbase tow vehicle (relative to the trailer) I would seriously consider a
Hensley hitch.

Bottom line, I would consider the ML for towing a trailer in the 25 foot
range, but I think you are likely pushing your luck towing a 34' Airstream
with it. I'm sure the Benz would work under most conditions, but the
question is how would it work under duress? (Which is when your neck is on
the line.)

A while ago, I was looking at the VW Toureg  as a possible tow vehicle.  It
is an awesome off road vehicle and the new 7 or 8 liter diesel engine has
incredible power and torque. (The diesel powered Toureg will out accelerate
its Porsche Cayenne stable mate with a twin turbocharged V8!).
Unfortunately, the Toureg has a unit body, and VW still hasn't figured out
how to design and install a high capacity, weight distributing hitch to this
frameless design vehicle.

Good luck, and keep us posted.

Sincerely,

Oliver Filippi