Mercedes ML350 Bluetec - How big a TT can I tow?

[Proteus]

New to this and need some advice. I have an ML350BTC as a tow vehicle. Plenty of power (455 ftlbs), and it has a 7200lb tow rating. I'm looking for a lightweight 25-28ft travel trailer with bunks (something like a surveyor sport, or passport). There is a huge difference in weight and construction..the ones I'm looking at come in right at 5000-5200lbs (delivered weight, from door sticker)

Question is, I've visited a number of RV dealers so far that seem to think you need you need a traditional truck to tow (although one changes his mind when I pointed out this was basically a fancy Jeep Grand Cherokee)

GVWR is 6504, RAWR - 3638, FAWR 3197, curb weight 5109.
This leaves me with a payload of #1395 (more than a "half ton" in truck speak). Tires are rated over 2100lbs each, so no issues there.
My hitch rating is low at 575lbs, since European standard is 8% on the hitch, not 15% like here. From what I understand, a good WD system will take care of that (locally, equalizer "four points" seems to be popular). Per the dealer, the MB has trailer towing software that automatically detects and corrects for sway.

So question is this: Can I safely tow something like:
Keystone Passport 2650BH (4950 dry, 470 hitch),
Coachman Captiva 270RS (4600 dry, 740 hitch, the WD should help here?)
or even a Surveyor cadet SC-280(4700, 504 hitch).

I know in Europe, people tow large boats and caravans with these, and even here in the US, the Airstream crowd tow the heavy 25-28ft models (and per youtube, apparently even the 7500lb 30fter!). At the same time though, there seems to be some great difference of opinion out there.

[hbillsmith]

Take it from someone who has actually towed comfortably and safely with a Mercedes for 2 years. Get the Anderson WDH. Its the lightest and the Mercedes 600 hitch weight needs an ultra light trailer. You can also add a hitch receiver (frame welded)to the trailer back and carry some weight back there to leverage off some tongue weight.

[brulaz]

Proteus wrote:

...
We looked at Lance but they only have one bunkhouse model, the 2185, and it's just too small. If they'd done double bunks instead of cramming a triple in the back, it might work, but it's stilll tiny. Couldn't even get the toilet door to close.

The Mercedes trailer mode basically automatically detects sway, and then cancels it through either alternate front wheel breaking (individually braking an opposite front wheel), or leveraging the AWD system to use engine torque to counter or slow. In practice, it worked really well, could definitely tell when it kicked in.
...

Yes, we found the Lance's too cramped as well.

Interesting about that AWD trailer mode. What we have in our trucks is the individual wheel braking part, plus overall speed/torque reduction to control sway. Not individual wheel torque management, if that's what you're describing.

My truck's sway control has never kicked in though. If it did I believe there would be an icon popping up on the dash. So I've always assumed it to be more for extreme, emergency situations, not normal towing.

But we have over 15% tongue weight, and occasionally, if I'm lazy, I leave off the friction sway bar without problem. Sway just doesn't seem to be an big issue with all that tongue weight.

[Proteus]

brulaz wrote:
Proteus:
Look at Lance trailers. Lower to the ground, light weight. If you don't plan to go off-road they would be great.

(We're going the other way though and planning to spend more time boon-docking off-road at remote locations, so not for us).

Curious about the AWD "trailer" mode. Can you describe what it's supposed to do?

We looked at Lance but they only have one bunkhouse model, the 2185, and it's just too small. If they'd done double bunks instead of cramming a triple in the back, it might work, but it's stilll tiny. Couldn't even get the toilet door to close.

The Mercedes trailer mode basically automatically detects sway, and then cancels it through either alternate front wheel breaking (individually braking an opposite front wheel), or leveraging the AWD system to use engine torque to counter or slow. In practice, it worked really well, could definitely tell when it kicked in.
One thing I forgot to mention was the importance of tire pressures. You have to make absolutely sure to inflate all tires to max. You also need to watch your pressures (ML will show you through the dashboard). If they start to get too high, SLOW DOWN. If you're towing a trailer, you BELONG in the slow lane. I've seen idiots driving pickup trucks who think it's perfectly ok to tow at 80mph. No, no, no. Trailer tires can't handle it, and towing a big trailer at that speed, especially with a bouncy, loose truck suspension is just a bad idea,

[Turtle_n_Peeps]

There was a guy here asking about horsepower. Horsepower relates to top speed and straight line acceleration, not hill towing. Why do you think some Cat semis are rated at "only" 400HP?

LOL, how lost can a person be? :S What do you think towing in mountains involves? Skip to 15:30 to 15:45 to see what they say about 420lbs torque towing. :B

Ya, I passed one of your 1400 lbs of torque engines today. He was clawing up a small hill at 22 to 25 MPH. :R I bet he had somewhere around 300 to 350 HP.

I think he wanted to wave but he was having a tough time steering and rowing through the gears like a mad man on meth just to keep the snails from overtaking him in the left lane. :B

If he would have had a Cat C15 with 625 HP on tap I bet I would have had a tough time passing him in my Acura. More than likely I wouldn't have needed to pass him because he would have been going the speed limit.

If you want to be stuck in the slow lane following the big rigs with your hazard lights on be my guest. I'll take high HP and be having an adult beverage in my campground while you're still pulling a mountain with your high torque rig. 😛 You want me to save you a space? You will be a while. :B

[carringb]

Torque determines the ultimate grade you can climb without stalling because its a measure of force.

HP determines how fast you will go, whether tackling grades or air resistance, as it's a simply a measurement of how much work can be performed over a period of time.

Torque can also be multiplied at the transmission and differential (or even at the axle hubs in transit buses and off-road equipment), but HP only gets lost through parasitic loses at each component is passes through.

[rjstractor]

Fuscus wrote:
Horsepower relates to top speed and straight line acceleration, not hill towing. Why do you think some Cat semis are rated at "only" 400HP?

It's popcorn time! 🙂 I'll only say one thing... the fact that semis only have 400-500 hp towing 80000 pounds is the reason you pass them on hills like they are standing still. If they had 1000 hp you would not be passing them nearly so easily.

[brulaz]

Proteus:
Look at Lance trailers. Lower to the ground, light weight. If you don't plan to go off-road they would be great.

(We're going the other way though and planning to spend more time boon-docking off-road at remote locations, so not for us).

Curious about the AWD "trailer" mode. Can you describe what it's supposed to do?

[Fuscus]

Hi, I came back with a few photos. I forgot to mention, I am using a WD hitch but my trailer's official tongue weight is 675 lbs. My ML's manual says maximum 575 (the Touareg TDI allows 660). The CanAm reinforcement is needed only if you do not have the latest version of the OEM hitch that uses a receiver bracket that goes around the main tube, so if the weld brakes the receiver is still attached. As a conclusion, the maximum comfortable length for an ML should be 25 FT (not 27 like mine), not very tall (mine is quite tall but good for forest use like I do), and most importantly it should have a posted tongue weight less than 575 lbs. The gross weight of the trailer should not be more than 6500 lbs. This is for a comfort zone, again. The two biggest problems I have are strong sudden crosswinds if I am traveling at more than 60 miles/hour and being illegal with a full load of water (over the GVWR). My Lite Trail Trek 27 BHS comes at 6000 lbs loaded (no water) (standard suspension, no Airmatic). My top speed was 125 km/h (77 miles/hour) and my lowest in strong storm winds 80 km/h (50 miles/h). A safe average is around 110 km/h (68 miles/hour). Power is jut awesome and I bought an ELM 327 Wifi OBD reader that sends all the temperatures and engine loads to my iPhone on the dash. It helps monitoring the stress on the vehicle. Low rpm torque is king, the ML may not win drag races but for long haul it is just perfect. The rumble of a gas V8 may sound nice from a stop light but when you hear that constant struggle for 6 hours at a time you get sick of it. It also happens to be terrible for fuel economy. I wish they sold the ML 420 CDI here with the 4.0 V8 diesel. It makes no sense selling it to Europe anyway, they have the ML250 Bluetec now with the four banger. There was a guy here asking about horsepower. Horsepower relates to top speed and straight line acceleration, not hill towing. Why do you think some Cat semis are rated at "only" 400HP? Just like a Hemi 1500. Will the Hemi tow a double train with 18 wheels? I don't think so. Gobs of torque they have. Besides, a gas engine puts that power at a high 6500 rpm. How often do you rev it that much? Rarely. The ML bluetec turns out 240 at 3400 rpm instead. More usable horsepower. Long story...Good luck and safe camping!

[blt2ski]

Proteous,

IMHO, you did quite well overall. Slowing to 50 mph on the steeper interstate grade with a motor of you specs is frankly, probably pretty normal. Even if you would have had something.g more aerodynamic, like an Airstream, you probably would not have been going that much faster. If at all, as you probably did what a lot of us do, when we realize we can not hold 60, 50 or what ever speed on a grade except by being something close to realize, we slow down to an rpm that is high enough to keep our speed up, yet have some cushion if we need to accelerate some. I'm going to swag your motor is simaler to the diesel in the sprinter I drive. Upper 2000 to low 3000 pulling a steeper hill, no issues if I can not he the gear above it.

BUT, as you say, a lower trailer, more aerodynamic etc would probably been more fun per say, I feel you could continue renting this trailer for a trip like this for years to come and not hurt your rig.

Marty

[Mike_E_]

Thanks for the real world update.
Thinking you would benefit from a 'lower riding' trailer like you have mentioned.
Trouble is.....finding one. Most of the newer trailers have the 3 steps up into it, adding overall height to the equation.
Our first Spree only had two steps, and it wasn't until we got our next trailer with 3 steps did I notice the difference in how it towed....feel and mpg. The differences were slight, but I could tell.
If the Nash's floorplan was agreeable, I just found a new KZ Vision that looks like it would fit the bill....and looks like only two steps up into it.
http://kz-rv.com/vision/V23BHS.html
Cheers,
Mike
BTW, great MPG towing the Nash.....has me re-thinking truck/trailer (have neither right now). Comfy SUV/trailer perhaps 🙂

[Proteus]

Thanks, just for an update on this, we decided to rent for a while, and took a Nash 25c (not ideal) from Seattle all the way to Yellowstone and Glacier. The trailer loaded was about 6200lbs, so within the 7200lb tow rating, and we used an equalizer 4 points wd hitch and prodigy bc. We did everything from broken roads, to long stretches on the plains with 40mph crosswinds, and did some nice long steep sections, including the continental divide.

So, this combo worked, but it wouldn't recommend it . The Nash rides high, isn't that aerodynamic and has a bouncier off-road suspension. The weight itself was fine..the diesel has plenty of torque (455) so pulling was never an issue, and was great for engine braking too. Going steep uphill on the long I-90 stretch over the divide, the little engine was working hard I had to slow to 50mph in sections (normally kept at 60-65). Trailer sway in crosswinds was noticeable, but the trailer mode in the AWD corrected everything nicely. Rain, thunderstorms, no problem, just slowed down some.
Oh, and I averaged about 13mpg towing (vs my normal 30 highway, not too shabby). I would NOT do this with a gas model. The diesel makes a huge difference. Note that the Jeep Grand Cherokee is basically the same thing. I have to say, was pretty funny seeing the occasional guy in pickup truck gasp as we passed them 🙂

Bottom line, I'd say a 4500-5000lb dry trailer is fine. I would make sure it has a proper (not bouncy leaf spring) suspension, and rides lower to the ground. It's a modern SUV and needs a modern trailer to go with. Airstream would also be great, but they're not family friendly (we need a bunkhouse.

[LarryJM]

naturist wrote:
There certainly is a great difference of opinion on this topic; get ready, you are gonna hear from 'em all.

I have a Jeep Liberty CRD, 335 ft-lbs torque, rated to tow 5,000 lbs. My TT is 21 feet, 5,000 lbs gross/3650 dry weight. And based on my experiences with this set up, I'd say you'll be fine with the Captiva or the Surveyer. The Keystone leaves a little less cargo capacity than I'd like to see, but it might be fine. I think your tongue weight capacity is too low, however. You might have to do something about that.

And yes, I'm sure there will be folks horrified at my rig, just as they will be at your proposed ones.

Unfortunately your experiences are not germane for the OP and are with a trailer not the same as what the OP is considering. His is taller and probably wider and weighs at least 1000 lbs more both dry and wet than yours. His is also almost 8' longer.

Larry

[blt2ski]

Do some of you realize, the OP is from July of 2013! this guy either has the rig or not! or should have it or not any who!

Marty

[LarryJM]

Proteus wrote:

My hitch rating is low at 575lbs, since European standard is 8% on the hitch, not 15% like here. From what I understand, a good WD system will take care of that (locally, equalizer "four points" seems to be popular). Per the dealer, the MB has trailer towing software that automatically detects and corrects for sway.

No any WDH does not effect that 575 number unless the receiver it's self has a sticker for a TW with and w/o WDH. Also, one is wise to have a WDH with integral sway since they all help prevent (or more accurately the amount or magnitude of the onset of) sway from happening in the first place thru friction whereas the integrated vehicle sway systems reduce sway once it has started by TV braking AFAIK. With typical sway systems one only uses the TV brakes when their intergrated WDH sway system has been overloaded or has failed to control a sway event.

So question is this: Can I safely tow something like:
Keystone Passport 2650BH (4950 dry, 470 hitch),
Coachman Captiva 270RS (4600 dry, 740 hitch, the WD should help here?)
or even a Surveyor cadet SC-280(4700, 504 hitch).

NOT IMO. You will exceed your receiver TW rating more than likely with both of those trailers.

Finally forget all this "EUROPEAN" thinking since trailers over there are VERY, VERY different in not only the dimensions (width and height smaller resulting in smaller frontal air resistance area), but in general length and weight.

Larry

[APT]

Proteus wrote:

My hitch rating is low at 575lbs, since European standard is 8% on the hitch, not 15% like here. From what I understand, a good WD system will take care of that (locally, equalizer "four points" seems to be popular). Per the dealer, the MB has trailer towing software that automatically detects and corrects for sway.

So question is this: Can I safely tow something like:
Keystone Passport 2650BH (4950 dry, 470 hitch),
Coachman Captiva 270RS (4600 dry, 740 hitch, the WD should help here?)
or even a Surveyor cadet SC-280(4700, 504 hitch).

A WDH does not change the TW. It just distributes the TW from the rear axle of the TV to the front axle of the TV and the trailer axles. For example, a 600 pound TW trailer:

Drop the tongue on the ball and rear axle goes up by about 850 pounds, front axle drops by 250 pounds. Apply WD to restore that 250 pounds to the front axle. Then rear axle is only about 450 pounds higher than unhitched and TT axles add 150 pounds. The receiver still experiences 600 pounds of TW.

If your receiver or vehicle owners manual states 575 pounds limit, I do not recommend exceeding it. Stick to dry weights at 400 TW and 3500 total dry. That should keep you near your TW limit.

Tow vehicle sway control is not something you ever want to experience activating. Use a quality WDH with integrated sway control such that you never have to activate the vehicle's systems. Equal-i-zer 4pt is a good product.

Verify your payload via the Tire and loading sticker on driver's door or door jam. When people list curb weight, that is usually base, not what typical people buy.