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

[Rick Kunath <k9ao@xxxxxxxxxxx>]

Oliver Filippi wrote:
> 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.
> 

Any travel trailer, for that matter. A boat yes. A travel trailer, no.

> 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.  

Absolutely. This rules out it's use as a tow vehicle for a travel 
trailer. Period. Even for a short trailer, this vehicle is totally 
unsafe. It would be a hazard to you, and dangerous to others sharing the 
road with you.

> Assuming the frame and drive train are strong enough, it
> should be OK. But here too, I think you are possibly pushing your luck.  

Ask Mercedes if they will warranty the frame against cracks when using a 
load-balancing hitch. There are tremendous forces transferred to the 
frame when using this type of hitch, and you *will* be using a hitch of 
this type. But, either way, the wheelbase is way too short.

> Granted, it
> does have a decent size (displacement) engine at 5 liters, though 6 liters
> or more would be a lot better.  

*Much* better. 5 liters is pretty marginal.

> 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.  

Directional change due to hitch vectorial force transfer is closely 
related to wheelbase, and suspension type isn't going to help you much 
there. The travel trailer is going to wag this little toy vehicle all 
over the road. Small movements imparted through the hitch will cause 
large variances in tow vehicle direction. I.e., squirrelly handling and 
probable sway resonances causing uncontrolled sway build up leading to 
jackknifing, roll over, unexpected lane changes, and ultimately damage 
to the vehicle, others around you, and you yourself.


> 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. 

The directional control system can't make intelligent decisions when the 
vehicle is a combination vehicle and includes a travel trailer.

> 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.

Like when a TT wags the vehicle's tail.

> A while ago, I was looking at the VW Toureg  as a possible tow vehicle.  It
> is an awesome off road vehicle 

You're kidding, right? A Toureg can't handle real off-roading. This is 
another cross-over vehicle. It's a nice design, but an off-road vehicle 
it certainly isn't. It isn't even a mediocre off-road vehicle.

My advice, avoid any of these little "cute" so-called SUV type vehicles. 
They aren't up to the task of towing, and are downright dangerous. If 
you're looking for something to get you to the grocery store in a snow 
storm, this might be the SUV for you. If you're looking for real 
off-road performance, these are not off-road capable. And, it isn't the 
right vehicle to tow a travel trailer.

Rick Kunath
WBCCI #3060