Towing with my 35D- load leveling?

[spyro235]

Originally Posted by bfeng

If you plan to tow with an X5, you should stick with those equipped with the air suspension. When I was shopping I specifically only looked for diesel plus 3rd row seats to make sure I had the torque and air suspension. It took quite a bit longer to find the right one to buy, but the X5 works great without bandaids and compromises.

Trying to tow with significant tongue weights without air suspension or WD would be a problem with most vehicles, not just the X5. You can sag out the back of a pickup too.
For that matter I’m surprised pickups don’t come with an OEM rear air bag setup for ride height leveling. These aren’t cheap vehicles anymore.

I bought mine for a steal- $4300 for my 35D. After a delete and a wheel bearing, I'm around 7k deep in a wonderful SUV that's still rated to tow 6000. This deal came along and I couldn't pass it up, as much as I would've loved to have the leveling suspension. I'm going to make do, and try to improve my car's setup, becasue it's rock solid reliable, and I plan on driving it for the next 150-200k miles. At the rate I'm going, that'll be 4-5 years, so I'd like to tailor it to my needs a bit. Most of my tows are only 50-70 miles each way, depending on which track I go to, but I'm going to make 2-3 distance trips, one of them being about 1000 miles each way. The X5 handled fine at highway speeds, I'd trust it to do it perfectly fine how it sits now, but if there's a way to improve the squatting, I'll give it a shot!

At the end of the day, I do wish the random crazy good deal I got happened to have the SLS, but beggars can't be choosers!

[spyro235]

Ok, since I always frown uopon posters that talk about trying something and never pull through.... I ordered a set. I measured my springs and found that the interior width is about 4.25" and the interior height is about 7.5" from perch to perch. Inputted into their "choose my set" forum at https://www.airliftcompany.com/works...ir-spring-kit/ and it came out with 60909, 8"long, 4" wide. They say its better to undersize the width a big than oversize, and emphasize that it will cause premature failure to oversize the width. There's a chance I should've gotten the 7" but their site said go with 8, and they have a lifetime guarantee on the product.

So, they should get here Thursday. I'm towing about 130 round trip to the track this weekend, so I'm going to see if I can get them installed before that. Still have some things to do to the track car before I go. I've got another event 2 weeks after that, so I wouldnt be too worried about running it as is for one trip, and then with the bags the next trip, as a comparison on the handling of the load. Regardless, when I get them, I'll post up some unboxing pics, and then I'll take some pics whenever I get aroudnd to installing them. As far as I can tell, I'll be the first person documenting aftermarket bags on a non SLS e70! Go me!

[bfeng]

Good luck with the bag test.

On our other German SUV without SLS I use a WD hitch, and that works quite well. That has the added benefit of weight transfer which SLS doesn't do for you. That's why despite having SLS, I also use a tongue weight scale for setting up how I load, and I keep the overall trailer weight under 6000lbs.

It's amazing that only Dodge equips their pickup trucks with airbags in the back for load leveling. I've always hated the stiff feel of a pickup with an empty bed. And at $100 or so, an airbag is an inexpensive consumable considering the benefit of load leveling.

Are you pulling and open or enclosed trailer?

[spyro235]

Lets see if that pic works- I'm towing a 18' open Big Tex. Two braked 3500# axles.

I haven't hit 6000# yet, and I really don't think I will. Car's about 3000 even, trailer is around 2100, maybe a hair over so I'll call it 2150.puts me at 5150, plus probably 6-800lbs of wheels and tires and random other stuff... so I suppose I'm probably cutting it close. The fact that you and a few others have accidentally hauled 9k+ makes me a little more comfortable with butting up against that 6k limit, and I certainly would rather play a little with the car's limit and have safe driving habits, than to play with the trailer's limit. The bags, if they do indeed work, will be a very inexpensive, great upgrade to the rear of my X5.

Still not sure if I'll be able to get my bags in before I tow the car home on friday evening, so I'm thinking I'll end up towing without them this time around. I might find time, but it depends on how today goes. Car's all back together and running great, new seat in, seatbelts hooked up, and I really just need to adjust the shifter a smidge and throw the rear bumper back on, and it's ready to be loaded up. I do really want to bring it home today if I can, so that I can get both my X5 and track car washed before my first event. If that ends up happening, then I might look at doing the bags tomorrow after I give everything a quick wash. Otherwise, they'll be in for the next event in 2 weeks.

[bfeng]

Remember, towing can be safe if
(1) I find that pulling a trailer exacerbates the negative effects any front end suspension/steering wear. Wear in a control arm that's tolerable under normal driving is a real pain when trying to keep a 8.5' wide trailer centered in the lane at 70mph on a rutted highway, in cross winds, in the rain, in heavy traffic.

(2) Not less than 10% of the total trailer weight on the tongue. I setup at about 12%.

(3) I try to get as much of the weight in the trailer over the trailer axles, to minimize the trailers tendency to porpoise over bumps. The std X5 rear shocks lack a bit of damping, in my opinion, when you've got 600lbs on the tongue and another 150 of gear in the cargo area. My jack, fuel jugs, spare tires, tool boxes, etc are all situated as close to the axles as I can get them to keep the vertical "polar moment" of the trailer low.

(4) You already know this, but drive like everyone around you is an complete idiot. I've had people try to merge onto the freeway and right into the side of my bright red trailer. I couldn't make it more obvious... So I tend to drive ridiculously defensively.

(5) Don't a rush. The difference between going 85mph and 70mph only makes 30-45min different in arrival time for where I tow. So, I tend to take it easy.

Good luck with your experiment.

[spyro235]

Originally Posted by bfeng

Remember, towing can be safe if
(1) I find that pulling a trailer exacerbates the negative effects any front end suspension/steering wear. Wear in a control arm that's tolerable under normal driving is a real pain when trying to keep a 8.5' wide trailer centered in the lane at 70mph on a rutted highway, in cross winds, in the rain, in heavy traffic.

(2) Not less than 10% of the total trailer weight on the tongue. I setup at about 12%.

(3) I try to get as much of the weight in the trailer over the trailer axles, to minimize the trailers tendency to porpoise over bumps. The std X5 rear shocks lack a bit of damping, in my opinion, when you've got 600lbs on the tongue and another 150 of gear in the cargo area. My jack, fuel jugs, spare tires, tool boxes, etc are all situated as close to the axles as I can get them to keep the vertical "polar moment" of the trailer low.

(4) You already know this, but drive like everyone around you is an complete idiot. I've had people try to merge onto the freeway and right into the side of my bright red trailer. I couldn't make it more obvious... So I tend to drive ridiculously defensively.

(5) Don't a rush. The difference between going 85mph and 70mph only makes 30-45min different in arrival time for where I tow. So, I tend to take it easy.

Good luck with your experiment.

I appreciate the words! I'm probably going to end up loading post of my wheels into my track car just for the ease of not having to tie them all down, so the weighting should be good. I've been running 10-11% tongue weight. I also spend a good amount of my fair weather time on two wheels, so I tend to be pretty good at knowing everyone is an idiot on the road! And-85 mph?! That's wild. I don't know if I'll ever push it past 75, as even that is pushing it in terms of comfort while towing so much weight. I'm hoping the bags end up really helping the handling, which seems to not even be that bad, but it can't hurt to try to improve.

[bfeng]

I don’t have the cojones to play on 2 wheels. I want to be inside not outside of the ODM tubing.

[spyro235]

Ok... Installed the airbags. The don't seem to be leaking, so I guess I plumbed them alright. I have them at 30psi now and don't really notice a difference in how it drives, but I'm hoping it helps the rear end out when I'm towing. I should be loading up the trailer tonight, and towing my car home in preparation for an alignment and lots of tires.

[bfeng]

Spyro,

This is really exciting. Waiting to here how it works out as it makes a larger group of X5’s suitable for towing duty (eg those without self leveling).

[spyro235]

Originally Posted by bfeng

Spyro,

This is really exciting. Waiting to here how it works out as it makes a larger group of X5’s suitable for towing duty (eg those without self leveling).

Bfeng- I just towed 30 miles home, at night, 1/3 through hilly windy county roads(35-45 mph limits) and 2/3 on a particularly hilly section of interstate (fr 80- 65mph). I was towing at 70 mph for the interstate. Rear bags are at 32-33 psi.

WOW! You can feel the weight, but there is much less “pushing” around from the trailer. The most noticeable difference is that the up-down bobbing over bumps from the trailer is entirely dampened out. Gone is the slightly wallow-y underdamped feeling of the rear end letting the trailer tongue pull it up and down, even over railroad tracks on local roads.

I currently have about 530 lbs of tongue weight, and I believe my trailer is likely right around 6300. That’s estimating on the very generous side, and I’m nearly certain that I’d be right around 6-6.1k on a scale. I’m going to up that tongue weight to right at 600 on my scale, which I measure at the tongue jack, which is about a foot and half back from the actual ball. This gives me a slight margin of safety on overloading the ball itself as per bmw’s recommended 600lbs max. I’m probably going to bring the bags up to 40psi. The car definitely squats a bit less, but it does still squat a bit. I’m hoping that a little more pressure evens it out with the slightly heavier tongue weight that I’ll be going with. I want a bit more stability for the long highway miles I’ll be doing come Thursday.



Overall, tomorrow I have to get my windshield sensor fixed by safelite first thing in the morning, and then go have the tire place mount 14 fresh tires on all my wheels. That’ll total to about 70 miles of towing, but will be a very busy day around that. Then, Thursday, I’ll leave on my 2200 mile journey. I’m not much of a man of god, but I’m beginning to pray for no issues! It’s a long way to be stuck from home...