Towing - Standard vs. Load-Leveling Suspension

[digdesign]

Hey Guys. I'm mew here. Been lurking on the forum as I've been shopping for a pre-owned E70 35d. Thanks for all of the useful info. Here's my question:

I'll be towing my E30 M3 on an open aluminum trailer. The total weight of the loaded trailer will be roughly 3800lbs (2590lb car + 900lb Trailer + 300lb spare tires & tools). Shooting for 10% tongue weight would put it at about 380lbs on the coupler. On top of that, I'll also have 170lbs of equipment in the back of the X5. So the total load on the rear axle will be in the ballpark of 550lbs.

My question is, does 550lbs necessitate the load-leveling suspension? I know that it will be "better" with it. But can anyone comment on the amount of sag I might experience with a standard suspension?

FWIW. I do want the load-leveling suspension, but it's hard enough to find a decent used 35d, let alone to find one with option 220 and no 3rd row. (I don't want the 3rd row since I'm towing long distances and need to carry a spare)

Any advice would be greatly appreciated.
Thanks
-Mick

[ninekrpm]

Lookup my post on the same subject matter. I tow around 4700-4800 pounds with my e70 X. It does not have the auto-level suspension; however I use load level bars, which I carried over from my e53 X. IMO, having towed between the two, I prefer the non auto-level suspension with the load bars - my current setup. I have towed for 4K+ miles already with my new X, including a 13 hour tow. Absolutely effortless and balanced.

And do not have to worry about a suspension damper breaking down.

[digdesign]

Thanks, I didn't see that thread in my earlier searches.

[blue dragon]

Originally Posted by ninekrpm

Lookup my post on the same subject matter. I tow around 4700-4800 pounds with my e70 X. It does not have the auto-level suspension; however I use load level bars, which I carried over from my e53 X. IMO, having towed between the two, I prefer the non auto-level suspension with the load bars - my current setup. I have towed for 4K+ miles already with my new X, including a 13 hour tow. Absolutely effortless and balanced.

And do not have to worry about a suspension damper breaking down.

You realize that BMW specifically states not to use weight distribution equipment. The X5 is a unibody, not a body on frame. WD will transfer the weight through the unibody to the front tires. I know people do it, if you search for user withdl, you will see he was towing an 8000 lb airstream trailer with a hensley arrow weight distribution hitch for many thousands of miles without problems.

The approved rear axle weight is also way less without the 3rd row/self levelling suspension. As per page 289 of my 35D owners manual,
Approved rear axle weight - 3858 lbs
without 3rd row - 3395 lbs

The gross vehicle weight rating changes too
Approved gross vehicle weight - 6614 lbs
without 3rd row seats - 6294 lbs

[digdesign]

Originally Posted by blue dragon

The approved rear axle weight is also way less without the 3rd row/self levelling suspension. As per page 289 of my 35D owners manual,
Approved rear axle weight - 3858 lbs
without 3rd row - 3951 lbs

The gross vehicle weight rating changes too
Approved gross vehicle weight - 6614 lbs
without 3rd row seats - 6295 lbs

That must be a typo' right? Approved rear axle weight is 93lbs higher when you don't have the 3rd row?

[blue dragon]

Originally Posted by digdesign

That must be a typo' right? Approved rear axle weight is 93lbs higher when you don't have the 3rd row?

Its higher when you have 3rd row seats (basically self levelling suspension). I fixed my typo

Here is the old post about towing with a WD hitch

http://www.xoutpost.com/bmw-sav-foru...airstream.html

[Bayerische E53]

Originally Posted by digdesign

Hey Guys. I'm mew here. Been lurking on the forum as I've been shopping for a pre-owned E70 35d. Thanks for all of the useful info. Here's my question:

I'll be towing my E30 M3 on an open aluminum trailer. The total weight of the loaded trailer will be roughly 3800lbs (2590lb car + 900lb Trailer + 300lb spare tires & tools). Shooting for 10% tongue weight would put it at about 380lbs on the coupler. On top of that, I'll also have 170lbs of equipment in the back of the X5. So the total load on the rear axle will be in the ballpark of 550lbs.

My question is, does 550lbs necessitate the load-leveling suspension? I know that it will be "better" with it. But can anyone comment on the amount of sag I might experience with a standard suspension?

FWIW. I do want the load-leveling suspension, but it's hard enough to find a decent used 35d, let alone to find one with option 220 and no 3rd row. (I don't want the 3rd row since I'm towing long distances and need to carry a spare)

Any advice would be greatly appreciated.
Thanks
-Mick

Hi Dig,

I used my E53 NON-SPORT to tow my open trailer and racecar; total weight was 5,000lbs with about a 550lbs tongue weight. I did not use a WD hitch with this setup and the truck towed a treat. There is obviously a bit of sag, but nothing absurd. I did around 10,000 miles with this setup without a hitch (no pun intended). At 380lbs tongue weight, you should be just fine.

Also notice that the weight on the rear axle will actually be more than 550lbs because the 380lbs you're exerting on the tongue is a lever, exaggerating the amount of weight on the rear axle. Either way, based on the weight I was putting on the tongue, you should be more than fine as I was within spec. Regardless, make sure to check your tongue weight with a scale to really get an idea of what weight you're placing on the tongue - the last thing you want to do is underload the tongue, making the trailer have a tendency to want to buck up and down, lifting the rear of the X5 (no stability).

Ideally, you'd want to use at least an "Equalizer" brand WD hitch, but it isn't terribly necessary - especially with only a 380lbs tongue weight.

[digdesign]

Based on the numbers we have, I should still be well under recommended limits.

With 3rd row & Load-Leveling
6614lbs Gross Weight Limit - 4700lbs Unladen Weight = 1914lbs Capacity
6614lbs Gross Weight Limit / 3858lbs Approved rear axle weight = 58% of load allowed on rear axle
58% of load capacity (1914lbs) = 1110lbs allowed over rear axle

No 3rd row & Standard Suspension
6294lbs Gross Weight Limit - 4700lbs Unladen Weight = 1594lbs load capacity
6294lbs Gross Weight Limit / 3395lbs Approved rear axle weight = 54% of load allowed on rear axle
54% of load capacity (1594lbs) = 860lbs allowed over rear axle

Does that sound about right? And is that 4700lbs unladen weight number accurate?

[digdesign]

Originally Posted by Bayerische E53

Hi Dig,

I used my E53 NON-SPORT to tow my open trailer and racecar; total weight was 5,000lbs with about a 550lbs tongue weight. I did not use a WD hitch with this setup and the truck towed a treat. There is obviously a bit of sag, but nothing absurd. I did around 10,000 miles with this setup without a hitch (no pun intended). At 380lbs tongue weight, you should be just fine.

Also notice that the weight on the rear axle will actually be more than 550lbs because the 380lbs you're exerting on the tongue is a lever, exaggerating the amount of weight on the rear axle. Either way, based on the weight I was putting on the tongue, you should be more than fine as I was within spec. Regardless, make sure to check your tongue weight with a scale to really get an idea of what weight you're placing on the tongue - the last thing you want to do is underload the tongue, making the trailer have a tendency to want to buck up and down, lifting the rear of the X5 (no stability).

Ideally, you'd want to use at least an "Equalizer" brand WD hitch, but it isn't terribly necessary - especially with only a 380lbs tongue weight.

Thanks, that's good to hear.
I don't plan to use a WD hitch. It sounds like if I distribute the trailer load correctly I should be fine.

[Bayerische E53]

Originally Posted by digdesign

Thanks, that's good to hear.
I don't plan to use a WD hitch. It sounds like if I distribute the trailer load correctly I should be fine.

Absolutely. Please make sure to have AT LEAST 10% of the trailer's gross weight on the tongue, though, in order to prevent instability. Most people usually shoot for somewhere between 10% and 12%. Some even go up to 15% - but don't go over that.

You should be fine with your 3,800lbs setup if you've got somewhere in the neighborhood of a 380-455lbs tongue weight.

One more thing, after reading your first post again I realized that you will be carrying spare tires and tools. Presumably you have a tire rack and tool box on the front of your trailer. All that weight is way near the tongue and exerts a larger force than if it were centered perfectly over the trailer axles (in which case it would exert zero force on the tongue). The longer your trailer, the more exaggerated this effect will be. With that setup, I'd definitely weigh your tongue weight. You honestly may not be able to offset that weight merely through the location of your car on the trailer.

How long is your trailer? Do you have a picture of it?

BTW, what do you race in; M3T?