Hello all,
I have a 2014 ML350 (gas) with factory hitch, and I recently purchased a travel trailer with 490lb tongue/hitch weight and 4300lb GVWR, they are well within ML's spec 6600lb/575lb. My problem is the weight distribution system the trailer dealership installed, I think it puts a lot stress to that factory hitch which it's not designed to handle - although MB doesn't say WD should not be used, the hitch ball rise/drop spec printed on the hitch (1-2 inches) indicates it's not supposed to take much rotating force.
After some research, seems like my options are:
1. Not using the weight distribution system, as the trailer weights are well within ML's spec. the downside is that the WD also does sway control the handling probably isn't going to be very good due to tilting.
2. Have the hitch reinforced - I live in Seattle area, and I just got off phone with Torqlift, their technician advised against such idea and decline to perform such work on the car.

I'd appreciate any suggestion/advice from the forum, thanks!

-Hovr

 

I had my 2010 hitch reinforced at Can-Am RV in Ontario CA. It braces against the rear crossmember and resists twisting. Cost $600. https://www.canamrv.ca/towing-expertise/
I don't know if it was really necessary but the hitch was really solid.
You can call Can-AM and they will give you or your welding shop instructions on how to do it. It's not that hard but they need to put a bend in 2" square tubing.
Or you can just call and chat about your concerns.

I wouldn't worry about the twisting with a WDH, with that light a trailer. The bar tension is not real high.
FWIW look at half ton pickups - their hitches are often pretty puny, compared to the M-B factory hitch. There is a lot of twist on most of those.
Plus the M-B factory hitch has reinforcements that fit into channels that are pretty stout. (If it's an aftermarket hitch it won't be as strong.)

Whatever you do, load your trailer so that you have 10-12% of the trailer weight on the tongue, to resist sway.

 

Thanks @mikapen !

Not sure if there is a easy way to measure tongue weight? I have recently changed 2 lead-acid batteries to a lithium one, and moved it from frame battery box to inside the cabin(still before axle), it's a 50lb reduction without counting the position change towards the axle. not sure if that made it more sway prone?

 

I use a Sherline scale to weigh the tongue. https://www.sherline.com/product/she...-weight-scale/
But you can use a bathroom scale and some ingenuity, see https://www.curtmfg.com/trailer-part...ers/learn-more

Once you get your initial readings on a loaded trailer, you can adjust the load for the best tongue weight and it won't change much. Unless you make big changes - then it's good to re-check.

 

In Europe the diesel ML350 with the factory towing package is rated to 3,500 kg (7,700 lbs) and so it the gas V6. The hitch, additional transmission cooling capacity and in particular the ESP system for the trailer sway control are second to none. Most aftermarket WD hitches I've seen would not only be inferior in capacity, but will almost certainly interfere with the ESP operation for the trailer, which is exactly why they are unapproved by MB. I have actually tried to upset the same ~6000 lb loaded trailer on purpose and I couldn't get it to budge at twice the speed that would get it swaying with any other tow vehicle. In other words, the ML is the nicest and safest tow mule I've ever had. If you have the factory towing package on yours, anything you do to the car to "improve" it would actually be a downgrade.

 

I agree with you that the ML350, especially in Diesel guise, is a stellar tow vehicle.
However we need to correct your terminology. The factory tow package is NOT a WD hitch - it's just a hitch (or Receiver).
The OP was talking about a WDH (Weight Distributing Hitch), which is an accessory hitch that redistributes weight. The factory will accommodate either a plain hitch (Weight Carrying) or a WDH.

ALL WDH's are aftermarket. And they are recommended for trailers >3,000#.

BUT no aftermarket hitches (not WDH) that I know of are as strong and safe as the factory setup.

AND HD cooling for engine and trans are standard even without the tow package. As are brakes that are more powerful than 3/4 ton pickups.

 

Where did I say that the factory hitch is a Weight Distributing hitch? I made no such statement or implication.

Yes, my point is that the factory hitch and tow package electronics are in many ways better than an aftermarket WD hitch.

 

There you just did it again in the highlighted text above.
And in post #5 above when you wrote "Most aftermarket WD hitches I've seen would not only be inferior in capacity, but will almost certainly interfere with the ESP operation for the trailer, which is exactly why they are unapproved by MB."
A WD hitch is a WDH. A WDH is not even an option on Mercedes.
WDH's are recommended accessories for pulling heavy trailers, only available in the aftermarket.

 

You must either be a member of QAnon and see things that the rest of us don't, or have trouble with basic reading comprehension. Which part of "aftermarket" did you miss or do you not understand?

Again, show me ONE place where I stated that the factory Mercedes hitch is a weight distributing hitch. I never made any such claim.

 

@mikapen, @Diabolis. thank you both for providing very valuable information on this topic. I knew the ML is a nice SUV but prior to reading your comments, I had no idea it's such a great tow vehicle! I just found that it actually beats most compact trucks in terms of towing capacity :O not to mention the interior finishing, cabin comfort. After the input from you guys, I don't think I'd do a hitch reinforcement, I will experiment with no WD to see how it feels. I actually didn't know the ESP would help trailer sway, obviously I need to read the manual.

Thank you again!

 

I actually bought mine as a tow mule for the race car, and it has since become a daily driver in addition to towing duties. The ESP programming is excellent - see https://media.daimler.com/marsMediaS...ml?oid=9904683 and https://media.daimler.com/marsMediaS...ml?oid=9904516 if you want to find out more how it works (and the ESP electronics and operation have improved in the W166 since the feature was first introduced ~15 years ago in the W164). In terms of comfort and safety, it beats every other vehicle I've ever towed with.

 

"TSA is an extra function of the ESP® Electronic Stability Program and shares its sensory system; no additional electronics are required for either the trailer or the trailer coupling."

Just to confirm, TSA is part of ESP right? my ML does have ESP but I haven't seen any mentioning of TSA.

 

If the car came with the factory towing package option, it has it. It will automatically enable it when you connect the 7-pin electrical connector from the trailer. When you see the message on the dash that the blind spot assist is disabled because you've connected a trailer, the TSA ESP functionality is on.

 

I highly recommend against towing a 4500# trailer without a WDH. If you do decide to risk it, please make sure you're loaded with at least 10% of the trailer total weight on the tongue. The factory manual stresses this for trailers over 3,000#. How have you verified the trailer weight? I agree that you probably could skip a hitch reinforcement, though.

Also be aware that the Trailer Sway Control kicks in only AFTER the trailer has begun to sway (severe, increasing oscillations). You DO NOT want to hope the electronics will recover a real sway event.
Here is the Sherline Towing Guide - the best, most factual treatise on towing, loading, and the reasons for sway. https://sherline.com/wp-content/uplo...ooklet_web.pdf

A good WDH with friction sway control is only a few hundred dollars, and an afternoon of setup. Here in the Gateway to the Rockies, it's clear that the rigs that need a WDH the most are the ones that are too macho, usually 3/4T and 1 Ton pickups. The laws of physics apply to them, too. Don't be that driver!

BTW without a WDH your headlights won't adjust to aim down the road, and you will be blinding oncoming drivers. As you force them off the road because you didn't quite make that corner - no steering!
It sounds like overstatements, but it's a pretty regular occurrence.

Your ML is a stellar tow vehicle, WITHIN ITS LIMITS.

 

Thanks @mikapen , I am pretty paranoid about safety. I already have the WD installed by my trailer's dealership, and seems like I will just stick to it. The whole reason I started the discussion is that I worried the WD would damage the factory hitch. But I'd take that over a fishtail any day.

 

Here's the factory manual: https://www.mercedes-benz.ca/content...13_M_Class.pdf. Please show us where it says what you claim above. Mercedes and BMW actually say the opposite - do not use WDH under any circumstances.

TSC detects and starts correcting trailer sway before the vast majority of drivers are even aware that the trailer has started to sway, let alone have acted on it - provided that they know what to do in the first place. And, the ML is not a rudimentary pickup truck.

A good bottle of scotch is also only a few hundred dollars, and after an afternoon of drinking it you will have have "improved" the towing ability of your ML about the same with both. In other words, installing an aftermarket WDH with friction sway control on an ML with the factory tow hitch and systems that work with it is about as useful as you getting drunk before you set off. WDHs are suited for vehicles with ladder frames, such as pickup trucks and body-on-frame SUVs (ladder frames can transfer tongue weight to the forward axle more effectively than a unibody frame such as the one used in the ML). If you are towing with a pickup truck, a WDH is indeed the way to go. If you are towing with a unibody ML, the WDH will make things worse both because it cannot do what its intended purpose is, and - if you get a WDH with friction sway control - because the TSC software in the ML is designed to work in conjunction with the factory hitch, not a system where you have now introduced a secondary pivot point which would counteract the actions of the car while it is trying to bring trailer sway under control. The TSC on the ML actively does what the friction sway control on WDH does passively. The two of them together can make things a lot worse than not having either one.

Not true. If you have the self-adjusting HIDs on the ML (that do the little "dance" when you start the car), the headlights will adjust regardless of whether you're towing a trailer or have 1,000 lbs of cargo over the rear axle.

This I agree with completely, namely that the ML is indeed a stellar tow vehicle within its limits. Trying to "improve" it however with an aftermarket WDH and/or a friction sway control is like cutting off your perfectly good legs so that you can use the latest and best prosthetic limbs. It's not a good option.

 

I could highlight just about everything in the above post and provide links to refute, but it's not worth the time. Just ignore it. He has shown that he knows little about towing, physics or how M-B electronics work. The claim that ladder frames are stiffer than a M-B chassis is an example.Or just read the label on the hitch to see that a WDH is specified, despite his argumentative and dismissive attitude.
In fact the entire recent post is an example of mis- and dis-information, and could be dangerous to follow.
If you are interested, go to the Can-Am RV website to verify. Also good reading is the Airstream forum, and it's easy to search for M-B towing threads.

 

Dude... you are freakin' spun. Unless you are dyslexic and can't help it, please go back to grammar school, lay off the peyote or whatever it is that you are ingesting and is making you delusional - but in any case, please refrain from giving people advice on things that have the potential to injure them or kill them because you clearly can't even a simple sentence. You sound like a broken record just spewing off whatever random thought pops into your head.

Again, your first and only example is COMPLETELY off the mark. Show me where I stated that ladder frames are stiffer than a M-B chassis. I wrote "WDHs are suited for vehicles with ladder frames". I really don't care how you inferred anything about ladder frame vs. unibody stiffness, but that happened inside your head - I made no such statement. "Read the label on the hitch to see that a WDH is specified"? Again, read the label on WHAT hitch? How did that pop into your head and how is it relevant here? The OP asked about towing a 4300 lb trailer with a Mercedes ML. If you're reading some label on YOUR trailer hitch that says that you need a WDH, that is FOR YOUR TRAILER. We don't know or care what YOUR trailer says, but that is not universally applicable to ALL trailers, is it? And, if your trailer hitch does say that you need to use a WDH, and Mercedes says that you should never put a WDH on an ML, then the ONLY logical conclusion is that you should not tow YOUR trailer with a Mercedes ML. It is not that you should follow the warning on the trailer but ignore the one on the Mercedes.

As for my knowledge of towing, physics and electronics go, I am an electronics engineer with a bachelor's degree in physics. For fun I race cars, and tow ether my own open aluminum trailer and car (with the ML), or am one of two drivers that tow the team rig, which is an enclosed 40" gooseneck trailer with two race cars and tons of tools and parts and which we tow with a dually RAM 3500. Yeah, I know nothing any of those things.

Please man... you sound like a nice guy, but obviously your brain is making some connections that don't exist. Save yourself the embarrassment and the frustration, and just go back to reading what YOUR trailer hitch says and enjoy the scenery. Please?

 

Thanks @mikapen , I really appreciate all the comments I received in w166 sub-forum, I have learned a lot - I am a bit embarrassed as I have owned this car for 6 years now and I know very little about it beyond the basic stuff
Speaking of Can-Am, I actually called Andy before I picked up my Airstream last year and he was incredibly helpful and WD + reinforced hitch was his recommendation. The problem is I can't find a shop with experience to do that kind of work, hence this thread.

Thanks again.

 

@Diabolis on "Mercedes and BMW actually say the opposite - do not use WDH under any circumstances." Could you please point me to where Mercedes says this? I searched the owner's manual and could not find any information WRT WDH.

Thanks!

 

Again, far too many mis-statements, or misunderstanding of the topics.
Again, there's not enough time in a day to address all of them, so I just highlighted one of them as an example.
As to "Read the label:" On the back of the ML, there is this black metal thingy. It's called a "hitch." It's not attached to a trailer -it's part of the tow package. On the hitch is a label.

I have attached a picture of the label, so you can see what it looks like. The label has information about weight limits, for both "Weight Carrying" and "Weight Distributing."

As to your "Show me where I said...." comments, please read your own posts to see "where you said."

Please stay away from me while pulling your "enclosed 40" gooseneck trailer with two race cars and tons of tools and parts" because it's clearly overloaded and dangerous. I have seen plenty of those while towing our (class winning and stage winning) race team's entries in the Carrera Panamericana, a 4,000 mile jaunt to Central America and back. Somehow, most survive, but it's not because of any Book Learnin - they (you) are pushing their luck.

As a wise person said, "Stop Digging." Please don't make us continually correct your misunderstandings.

 

I attached a WDH setup guide from Andy. It's a good one, and people who have used it swear by it. Using his "equal depression at each corner" technique instead of repeated trips to the CAT scales is a lot better for fine tuning the setup. Cheaper, quicker and better.
On a trip east through Kansas, into 50mph front quartering winds with gusts to 70, there were several semi's and MANY 3/4T and 1 Ton pickups on their sides, our ML was rock solid after using that setup guide. I slowed to 55 because fuel economy suffered the most.

 

LOLOL. That's a beotch slapping if I ever saw one.

 

You are attaching a label from an AFTERMARKET hitch, made for a W164 to boot. Yeah, nice going bud... you've got this.

 

Are you getting a room for you to get yours?

Once a douchebag, always a douchebag.