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jmcarter · 02-10-2013, 04:50 AM

Quote:

Originally Posted by SafariSS

Here is my GL, wiring it up via factory green plug for trailer brakes. Can't wait to try it towing.

Very nice...picked up our new GL350 this past week. Have made the obligatory phone call to Andy for peace of mind. We have a 28 ft International and using a 3P. Will get to the CAT scales this week, trying to make sure I don't overload either axle (or tires) because with the GL's very capable air suspension and 1400 pound bars I can do just that and everything still look great. Pics to follow....

switz · 02-10-2013, 09:05 AM

The ML 350 gas engine is no powerhouse as compared to the diesel version.

When I took the nearly loaded 2013 25FB International across the scales (vs the new empty trailer coming home) there was a different sound from the engine department and it was working harder. The fuel mileage display usually shows around 28 mpg car only. It dropped from the displayed 17/18 when the trailer was empty to 13/14 mpg when loaded. I think the gas engine will be running at much higher rpms all the time to move on the level and will be challenged even by the low mountains on the east coast. There is a good chance the mpg would drop into the single digits.

At the dealership before even hitching the trailer to the car, the tongue weight was 1,150 pounds vs the literature weight of 833 pounds. About 140 pounds of the increase was the Hensley hitch head. The added street side awning, rear awning, solar panel and power cords and other associated "new gear" from the dealership were in the front storage area.

My wife and I were in the car with about 60 pounds of stuff in the rear. The fresh water tank was full in the trailer and there was lots of stuff in the coach. The scales reported that the front axle was overloaded by 54 pounds and the GVW was exceeded by 180 pounds. There was about 200 pounds of capacity left on the rear axle.

The big issue was that the dealer service manager stressed that the towing capacity of the 2007 ML 320 CDI was 5,000 pounds. I figured the 25FB was close to 7,000 pounds. The newer model MLs have a higher tow rating closer to 7,000 pounds.

Thus, I decided that too heavy of a towing load by a wide margin and exceeding GVW and the front axle rating would put me into an indefensible legal position if there were ever an incident.

The ML will stay in my driving stable for years to come as it is one of the most comfortable driving vehicles I have ever owned. I can safely tow the single rail motorcycle trailer with my Gold Wing aboard for service locally.

I acquired an end of year 2012 Dodge 2500 Cummins diesel pickup (no urea tank to contend with) that has the correct numbers to tow even a 31' Airstream plus equipment in the bed of the truck. I removed the factory receiver and installed a 2,550 pound rated receiver with a side benefit of the receiver opening being only about 4" above the Hensley hitch opening (a drop of over 9" from the stock configuration). The steel springs were removed front and rear and replaced with a Kelderman self leveling air suspension system which significantly softened the ride and it will always be level regardless of the load. The under bed fuel tank was changed from 34 gallons to a 56 gallon tank.

And it fits in my garage in the same bay in which the ML 320 was parked.

YMMV

mefly2 · 02-10-2013, 10:44 AM

Switz-It is a tight fit in our garage, but it is hard to beat that 2500 Cummins for torque and ease of towing ... the tow / haul mode is really nice with the compression brake when descending the steep mountain passes... no tail wagging the dog.

tuffr2 · 02-10-2013, 11:27 AM

Are there any legal ramifications from using undersized TV's. Just curious as I have towed with undersized TV but was never in an accident. Was I just lucky?

My concern now is:

1. Will my insurance cover my liability if I am using an under sized TV?

2. Will the officer notice or ask about the TV and is it possible I would be faulted even if it was not my fault?

SafariSS · 02-10-2013, 06:16 PM

I know if there is a serious accident or god forbid a fatality a accident claim lawyer would have a field day trying a case like that.

vonzellen · 02-10-2013, 10:52 PM

So, just a reminder, I'm the guy that started this post trying to figure out whether or not I could tow a 25FB with my 2012 ML 350 (gas). Those of you with the Mercedes diesel have said you think it would be underpowered. The 2012 ML 350 has 302 hp at 6500 rpm and 273 ft. lbs. of torque at 3500 rpms.

Should I keep this and give it a shot (beefing up the hitch at CanAm)?
Get the diesel version of the Mercedes ML?
Get a diesel truck?

switz · 02-10-2013, 11:44 PM

From memory as the car and books are a long ways away, the 2007 ML 320 CDI had about 395 ft pounds of torque from 1600 to 2600 rpm and the Horsepower was reached before 3000 rpm. Normal driving rpm at 75 was about 2200 rpm, right in the middle of the power band. 55 mph was about 1850 rpm in 7th.

When towing the empty Airstream home from the dealership at 55 mph, I did shift down to fifth on some steeper climbs coming East out of Los Angeles on I-10 so as to not lug the engine and transmission.

Horsepower comes into play at higher speeds, but the torque is what gets the rig moving and going up hills.

The referenced Mercedes gas engine speeds above tell me that you will have to select much lower gears out of the seven speed transmission with higher engine rpms in order to have the power necessary to move down the road or through hilly terrain.

If you are close to CanAM, then try the hitch modification for around $500 plus. I drove 4,400 miles round trip to find out I needed more payload after connecting the trailer to the car.

The 25FB has most of the storage under the front bed which makes loading an issue. That is just the logical place for the AC power cords, misc small tools, water hoses, wheel chocks, etc.

I was told to not load up the back end of the trailer trying to counterbalance the stuff under the bed as the frame lacks the strength to pull that off very well.

I am not a lawyer, but I think a term called criminal negligence comes to mind when a person knowingly operates a (fill in the blank) outside of it's design parameters and injuries could be reasonably be foreseen if there were an accident caused by the deviation from the vehicle specifications either in the short term or long term.

I would strongly suggest posing a hypothetical question to your vehicle insurance carrier representative about their coverage if your vehicle is intentionally operated in an overloaded condition or is considered by the main stream to be undersized for the job.

Just because the smaller vehicle can get the rig moving does not mean that the smaller brakes can stop the rig if the trailer brake controller decides to quit during a steep hill descent.

YMMV

Airstream Annie · 02-10-2013, 11:49 PM

It also has a 7 speed transmission which gives you plenty of gears to keep the revs up. While I have not towed with it I did have anearlier version of the ML with the 3.2 . I found there was plenty of power and lots of torque. It surprised many sportier vehicles. Having said that, the deisel has a lot more low end grunt. The question is do you want to pay the extra money for a new one as your vehicle is relatively new. I would suggest you speak to Andy about it. Either bring yout trailer or borrow one from Can Am and tow it up and down some of the larger hills in the London area. I'm sure he would have no problem with this. You can then get a feel for the rig and see how it behaves.

jmcarter · 02-12-2013, 02:16 PM

Having towed with both a Dually Cummings and a high torque gas SUV (QX56) there's really no comparison between the two. Towing our 28 ft International was fine but downshifting at the slightest hint of a overpass or grade was disconcerting and sometimes annoying. The Cummings never knew the AS was back there. That said, if we were camped somewhere for an extended period of time the Dually was tiresome for my wife to drive and park, which led to our transitioning over to a nice SUV. I felt the redesigned 2012 ML was too small for our AS and we bought a QX as a bridge vehicle (I'm not frivolous by any means, there were some unique circumstances that minimized the depreciation on the QX) and now we've just moved into our 2013 GL Bluetec and we are ecstatic with our choice. Both of the redesigned M-B models are light years ahead of their preceding models and have vastly improved hitch structure (and yes, I've had conversations with Andy as well), so think its just a matter of your needs and what the TV's other purposes are. Think your current ML is adequate for a 23/25 with hitch reinforcements but torque curve being placed higher in the RPM curve will be very noticeable compared to a diesel (new Bluetec V6 has the whole 455 lbs on tap at 1600 RPM).

SafariSS · 02-12-2013, 07:13 PM

JM, so did you beef up the hitch for the new GL?

I had a 13 GL on order then my neighbor had to move overseas, he had a crazy clean 12 model so I bought it when my build date got moved back to later March. GL is a awesome vehicle, have not towed with mine yet.

jmcarter · 02-13-2013, 04:31 AM

Quote:

Originally Posted by SafariSS

JM, so did you beef up the hitch for the new GL?

I had a 13 GL on order then my neighbor had to move overseas, he had a crazy clean 12 model so I bought it when my build date got moved back to later March. GL is a awesome vehicle, have not towed with mine yet.

Based on my conversation with Andy there is no urgency to do any additional mods an my 13 model, he's just going to add one longitudinal brace to combat twisting since I have a lot of tongue weight. He indicated that I should just keep an eye on it until we get up there during our summer Michigan trip. Based on what I've read I think you better call Andy to get some particulars on reinforcing yours sooner rather than later on a 12 model. He can probably recommend a place in Texas for the mods, hope it doesn't require relocating the DEF tank on the GL. Search the forum for Mercedes, ML350, Bluetec, etc and you can see there is pretty much a consensus on the great towing capability of the M-B but the hitch structure needs to be addressed if you've got a lot of TW.

switz · 02-13-2013, 07:23 AM

The 2013 Mercedes specification for the maximum towable GVW trailer weight is 7,200 pounds for the ML and 7,500 pounds for the GL V6 diesel models. Thus the 25FB International GVW of 7,300 pounds would be 100 pounds too much for the ML but under the allowance on the GL.

I wonder what their V8 diesel ML and GL models, built only in Alabama and sold nearly anywhere outside of the US, ratings would be for trailer GVW towing capacity?

One needs to carefully utilize the scales to avoid over loading the front axle on these two models with weight distribution hitches. The door label on my 2007 ML 320 CDI stated the maximum front axle capacity is 3,086 pounds. With just me (225 pounds) in the car and no trailer attached, the scales reported the front axle was loaded to 2,940 pounds which left 146 pounds of capacity for the wife and her stuff plus whatever the hitch moved forward.

YMMV

murreywalker · 02-13-2013, 07:49 AM

Hitch ability aside, I have towed our 23FC over the Rockies and frequent the Arkansas Boston Mountains. I know what my GL 450 is capable of.

Regardless of terrain (and a receiver that's been fortified to 10,000 pounds of tongue weight), I would NOT have much confidence in a 350 Blutec or gas engine to do much with a trailer longer than mine.

Good luck.

jmcarter · 02-19-2013, 04:24 AM

Just concluded a 300 mile trip with our 2013 GL350 pulling a 2010 28ft International using the 3P. Took a stinger adjustment (the M-B air suspension is going to make the truck level, no concern there) to get the AS level and several bar adjustments and subsequent re-weighs at the scales to get her under GVW on both axles with the whole famdamily and full tank of diesel. 15.3 MPG matches what the Cummings dually did over the same loop and of course the M-B was much nicer for other duties. Not towing and over 70% highway/ 30%city mixed driving is yielding ~27 mpg so think I'm rounding the bend on getting a great combination. Next step is putting the old weight distribution hitch on her to see if I can get further under GVW on both axles. Recognize the thread concerns a ML & 23/25 AS combination but my experience may be helpful for those considering the M-B family as a TV.

SafariSS · 02-20-2013, 05:46 AM

JM, thanks for your towing report. How much was your rear axle weight once adjusted?

Other thing I was wondering is Rich Luhr mentioned turning the car off when hitching then allow the car to level. Is this your experience?

jmcarter · 02-21-2013, 03:42 AM

Quote:

Originally Posted by SafariSS

JM, thanks for your towing report. How much was your rear axle weight once adjusted?

Other thing I was wondering is Rich Luhr mentioned turning the car off when hitching then allow the car to level. Is this your experience?

I got the rear axle loading down to 100 pounds less than rated capacity with full fuel tank, dogs, gear and my wife and I in the car (350 pounds under capacity on the steering axle). AS had almost full load of propane but nothing in the tanks. That took 7.75 inches of travel on the 3P jacks and Sean indicated I could go more, which I may do but probably not till CanAm does a longitudinal brace on the hitch since you introduce a lot of twisting motion when you transfer that much weight. I'd prefer to have some extra margin but the 28 International is rated to have over 900 pounds of tongue weight plus the 3P mass so I'm going to keep experimenting with trailer loading to see if I can gain some more and put a bit more on the trailer axles (which showed only 5600 pounds). With the current setup my rear tire pressure grew only one PSI more than the fronts BTW.

I recognize that we should make the hitch hookup measurements prior to the M-B auto leveling occurring and I was able to do that but noticed during a subsequent hook that the auto leveling started working with just the Keyless FOB in proximity to the ignition which was turned off...just haven't read the manual enough to determine if I need to pull a fuse or just remove the FOB completely.

Going to be interesting to chase this rabbit some more, having to order the 7 pin adapter to eliminate the blinking AS LED taillights, to which I mutter about German Engineering but dang if they didn't design one heck of a vehicle, we love it.

panheaddale · 02-21-2013, 06:59 AM

Here we go again with towing. The manufacturers give numbers for a reason. That is the safe towing loads recomended for that particular vehicle. You can always pull more weight that what is recomended for that vehicle but you are getting into alot of gray areas as far as the legal end of things.If you have an accident and someone is injured a lwyer will have a field day with you. He might not win but it is going to cost you alot of time and money and then you are alway going to wonder if you had not exceeded the recomendations would this have happened. We are not canada we are the US. Whatever they want to do up there they can do I wish it would stay there. I pull campers from the manufacturers to the dealers for a living. I see all these combinations on the road that everyone talks about and you really would be amazed at how much some wonder all over the road but I am sure they think they are in control because their vehicle rides great. I really wish the same rules applied to the general public as does to somone like myself that towes for a living. If DOT catches me even 1 pound over weight it is thousands of dollars in fines. "REMEMBER JUST BECAUSE YOU CAN TOW IT DOESN'T MEAN YOU CONTROL IT OR STOP IT.

mefly2 · 02-21-2013, 07:31 AM

Quote:

Originally Posted by jmcarter

Just concluded a 300 mile trip with our 2013 GL350 pulling a 2010 28ft International using the 3P. Took a stinger adjustment (the M-B air suspension is going to make the truck level, no concern there) to get the AS level and several bar adjustments and subsequent re-weighs at the scales to get her under GVW on both axles with the whole famdamily and full tank of diesel. 15.3 MPG matches what the Cummings dually did over the same loop and of course the M-B was much nicer for other duties. Not towing and over 70% highway/ 30%city mixed driving is yielding ~27 mpg so think I'm rounding the bend on getting a great combination. Next step is putting the old weight distribution hitch on her to see if I can get further under GVW on both axles. Recognize the thread concerns a ML & 23/25 AS combination but my experience may be helpful for those considering the M-B family as a TV.

What load range tires do you have installed on the MB?

jmcarter · 02-21-2013, 07:57 AM

SafariSS, you can PM me with any other questions. Thanks

vonzellen · 02-24-2013, 11:27 AM

After listening to all your valuable input for the last few months. . .

After talking to Andy and John at CanAM RV. . .

After talking by phone to several guys towing with the ML. . .

I made the decision to get the hitch on my 2012 Mercedes ML350 (gasser) beefed up at CanAM. I drove there Thursday and had the reinforcement done on Friday. These guys are pros and the work was perfect and $100 less than originally quoted. Andy also fabricated a new shank for use on my existing Reese WD hitch and explained how to best set my car up for towing. They were a great help. Thanks Andy, Kirk, and Andrew and Kim.

I may be under powered, but I'll see how it works in the flatter areas of the East Coast and if I find I need more power I'll consider another TV. (my ML350 actually has pretty similar hp and torque to my 99 ford f150 5.2liter gas)

The hitch modification/strengthening is quite simple, but elegantly done.

I plan to head to Florida in a week or two to pick up my 2007 25FB International.

One question though. . . there is some discussion about an adapter so that the lights in the Airstream work?? Does anyone know if this will be a problem with a 2012 Mercedes ML350 and a 2007 Airstream FB CCD??

And, again, thanks for everyone's help.