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  #91  
Old 11-09-2018, 08:08 PM
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I agree it would seem that tongue weight is too high, but we didn't directly measure it. I purchased a tongue scale this weekend and we're going to measure the trailer, as is on Sunday. Not loaded with water, stuff or a full set of propane tanks. Ideally we'd like to keep it below 750lbs.

We've made a lot of modifications to our trailer to make it an ideal boon-docking trailer. As we camp off grid a lot, namely a big battery bank on the tongue 4x6V golf cart batteries 60.5lbs each, plus 2/0 wiring, etc. for the inverter. Which was added to the tongue. The trailer actually towed better after the mods.

In order to actually measure tongue weight we would need to way the tow vehicle by itself, and the trailer with wdh on and off. We only measure the rig with WDH on. We did weigh more than 1x that day mainly because we were learning how to weigh, then moved on.

So all of this may be inaccurate.

Last edited by Thecastle; 11-09-2018 at 08:20 PM.
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  #92  
Old 11-09-2018, 08:17 PM
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I've weighed disconnected before. Ask first. We needed to weigh the force on the front feet of a 5th wheel.

If you weigh with and without the distribution bars stressed you will get the tongue weight also of course weigh truck without trailer.

I would get the tongue weight down you are over rated weight I think about 6000 gross is limit but not sure if you are allowed to go higher by adding tongue on top since it's low Cg. I've weighed in at 6600 myself but my run on flat tires are rated 500# each more than my previous tires.
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  #93  
Old 11-10-2018, 01:10 AM
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I am only boon-docking. My mods include: lithium batteries 400Ah, 2800 Magnum inverter, 640W solar panels. I ordered the trailer with two 20 lbs tanks instead of 30 lbs and relocated the batteries to inside the trailer to keep the tongue weight lower.

If you want to lower tongue weight you need to relocate batteries. You can use AGMs and put them in the trailer, if you do not want to spend $ on lithium.

Over 14k towing miles later, X5 is great tow vehicle. We towed through Rockies, many times in Tahoe, Yosemite, etc.



Quote:
Originally Posted by Thecastle View Post
(...)
We've made a lot of modifications to our trailer to make it an ideal boon-docking trailer. As we camp off grid a lot, namely a big battery bank on the tongue 4x6V golf cart batteries 60.5lbs each, plus 2/0 wiring, etc. for the inverter. Which was added to the tongue. The trailer actually towed better after the mods.
(...)
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  #94  
Old 11-10-2018, 09:58 AM
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my first trailer had a WD hitch and it could transfer 250-300 lbs from the rear to the front axle without any problems. But the real solution was to get a trailer which took me from 8500lbs to under 6500 fully loaded, and to arrange my load so the tongue weight is always 10-12%. I also setup the trailer for different loads and made notes so I don’t have to use my weigh scale unless it’s a completely new-to-me cargo.

The BMW hitch isn’t very beefy in terms of how it mounts to the e70 or how the receiver is attached to the cross bar. So I’d not use a ton of WD long term, but once in a while is probably ok.
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  #95  
Old 11-11-2018, 01:34 AM
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I think that the mounts to the unibody are strong with significant margin. I agree that the long drop plates between the cross bar and the receiver are the weakest point. Therefore, I reinforced the hitch, including adding a metal strut between the receiver and the axle carrier (Can-am type of mod, if you want to google for photos). I am using ProPride hitch, which probably generates more stress on the receiver than usual WDH. No problem so far.

Quote:
Originally Posted by bfeng View Post
(...)

The BMW hitch isnít very beefy in terms of how it mounts to the e70 or how the receiver is attached to the cross bar. So Iíd not use a ton of WD long term, but once in a while is probably ok.
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  #96  
Old 11-11-2018, 09:53 AM
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Quote:
Originally Posted by bono View Post
I think that the mounts to the unibody are strong with significant margin. I agree that the long drop plates between the cross bar and the receiver are the weakest point. Therefore, I reinforced the hitch, including adding a metal strut between the receiver and the axle carrier (Can-am type of mod, if you want to google for photos). I am using ProPride hitch, which probably generates more stress on the receiver than usual WDH. No problem so far.

The BMW hitch design is not as good as other German SUV's, and I have less confidence in its design for overloading or WD. I say this even though I've had no problems in 2 years of towing a 5000lb rig and a few trips with a 9000lb trailer with a big arse WD setup. Everything remains tight and the hitch has not shifted or bent even 1mm.

But while our old SUV (W164) has a similar tubular hitch but it's overall stronger in construction plus it has 2 cast iron torsion arms that extend almost 2ft up into the uni-body bumper reinforcement tubes. These help both with distributing the tension load away from the 8 bumper mount bolts and provide support for rotational or torque loads due to high tongue weight or WD.

Mercedes instructions to us did not exclude use of WD but BMW does. So, depending on what and how you tow, I'd be careful about assuming how much safety margin you have in the hitch and the attachment to the vehicle body.

Of course you are right that all OEM's design in safety margin and validate OEM parts/designs with very rigorous testing that goes beyond the recommendations in the official user documentation. But unless you know the specifics of the test, I'd err on the side of caution.

If you are going to regularly tow 20-30% over the rated limits and use 1500lbs of WD torqe, I'd highly recommend you have the hitch and it's attachment scheme strengthened. Any good automotive custom fabrication shop should be able to help with this work.
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  #97  
Old 11-11-2018, 12:36 PM
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Quote:
Originally Posted by bono View Post
Your tongue weight appears to be too high and I would try to go down. You do not need more than 10% TW, unless you tow 80 mph.
Lol, very easy to do with the X5M, to tow too "fast." Generally I like to go depending on weather (wind) and traffic around 65-75mph.

Though I was watching someone tow their 5th wheel montana at a constant 85mph on my recent trip to kentucky.
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  #98  
Old 11-11-2018, 01:48 PM
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Quote:
Originally Posted by Thecastle View Post
Lol, very easy to do with the X5M, to tow too "fast." Generally I like to go depending on weather (wind) and traffic around 65-75mph.

Though I was watching someone tow their 5th wheel montana at a constant 85mph on my recent trip to kentucky.

Make sure you have trailer tires with the appropriate speed rating. I threw away a nearly new set of Carlisle Ďs and put on a set of the new Goodyear Endurance tires. Tread wear doesnít look like itíll be phenomenal, but between my friends and I no blowouts in 2 years, and yes one guy tows a fifth wheel at 85moh cross country. But then again he has 900ft lbs of torque. As good as the X5 is, his makes an X5M feel gutless when pulling up steep hills.
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  #99  
Old 11-11-2018, 02:19 PM
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E53 (predecessor of E70) had those torsion arms as the hitch assembly. E70 unibody is significantly stiffer than E53 and maybe this is the reason why BMW came to the conclusion that arms are not required. Also, other German brands do not use the arms in the hitch assembly and they are OK for WDH.

Anyway, I have done robust reinforcement, so I am not concerned about the hitch.

Quote:
Originally Posted by bfeng View Post
The BMW hitch design is not as good as other German SUV's, and I have less confidence in its design for overloading or WD. I say this even though I've had no problems in 2 years of towing a 5000lb rig and a few trips with a 9000lb trailer with a big arse WD setup. Everything remains tight and the hitch has not shifted or bent even 1mm.

But while our old SUV (W164) has a similar tubular hitch but it's overall stronger in construction plus it has 2 cast iron torsion arms that extend almost 2ft up into the uni-body bumper reinforcement tubes. These help both with distributing the tension load away from the 8 bumper mount bolts and provide support for rotational or torque loads due to high tongue weight or WD.

Mercedes instructions to us did not exclude use of WD but BMW does. So, depending on what and how you tow, I'd be careful about assuming how much safety margin you have in the hitch and the attachment to the vehicle body.

Of course you are right that all OEM's design in safety margin and validate OEM parts/designs with very rigorous testing that goes beyond the recommendations in the official user documentation. But unless you know the specifics of the test, I'd err on the side of caution.

If you are going to regularly tow 20-30% over the rated limits and use 1500lbs of WD torqe, I'd highly recommend you have the hitch and it's attachment scheme strengthened. Any good automotive custom fabrication shop should be able to help with this work.
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  #100  
Old 11-11-2018, 04:17 PM
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“other German brands do not use the arms in the hitch assembly and they are OK for WDH.”

Thats true, our Mercedes SUV (which has the longitudinal tow bar reinforcements) isn’t a German brand. I think one of the Chinese company’s bought them a few years ago, Geely right?
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