Question for BMW X5 owners

[zetatre]

Ehi guys,

I've been reading this board for some time now and find it very useful... I've been around BMW boards and forums for some time (you may recognize my screen name) but usually the discussion about towing on those board end up like discussion on engine oil... if you know what I mean...

In any case. I read there's quite a few folks towing big rigs with their X5.

I have a 2009 X5 35d. It is fitted with the OEM hitch & harness (I installed it but had BMW do the coding) as well as the OEM BMW brake controller.

I've been reading people mentioning "reinforcing the hitch" and even saw the pictures that CanAn has on their FB page.

Could anyone elaborate on what exactly is happening that requires the reinforcements?

I would also love to see pictures of what people have done as reinforcement. What CanAm has doesn't show how the brace is attached to the frame.

Thanks!!!!

[jcl]

Originally Posted by zetatre

Could anyone elaborate on what exactly is happening that requires the reinforcements?

It does depend somewhat on which vehicle is under discussion, and in the case of the X5 whether it is an E53, E70, or whatever. Yours is an E70 based on the year of production. The OE (dealer installed) E53 receiver hitch included two longitudinal reinforcements to the unibody in the kit, to spread the load, and so didn't require additional aftermarket reinforcement.

The BMW E70 OE hitch is attached fairly solidly to the rear unibody. The reinforcement is specifically to deal with the additional twisting moment applied by a weight distribution hitch, and particularly with a larger trailer. All the reinforcement is doing is spreading the legs of the tripod, so to speak, so that there is an attachment point forward of the mounting flange for the receiver, to resist the twisting moment.

There is some other reinforcement sometimes done (not specific to the X5) which is to strengthen the receiver crossbar at the outboard ends, where it attaches to the brackets.

Given that the towing limitation of these types of vehicle is often tow vehicle payload capacity, it makes sense to get weight distribution dialed in to spread the load between the tow vehicle axles. That means you don't want the receiver flexing.

Jeff

[zetatre]

JCL, good to see you here too: your contributions are always extremely valuable.

Yes, the car is an E70.

Let me first confirm something very basic -> the purpose of all those reinforcements are to reinforce the receiver itself NOT the chassis, right?

[Road Ruler]

Originally Posted by zetatre

Let me first confirm something very basic -> the purpose of all those reinforcements are to reinforce the receiver itself NOT the chassis, right?

By the nature of reinforcing the receiver the chassis stoutness may possibly be improved too.

[jcl]

Originally Posted by zetatre

JCL, good to see you here too: your contributions are always extremely valuable.

Yes, the car is an E70.

Let me first confirm something very basic -> the purpose of all those reinforcements are to reinforce the receiver itself NOT the chassis, right?

Reinforcements to the receiver itself are often to the welds at the outer ends of the cross bar, on some specific hitches. That isn't specific to the X5.

Reinforcements to the X5 are generally to improve the interface between the receiver and the unibody/chassis. The unibody is very strong itself. What is important is spreading the loads from the hitch to multiple points on the unibody. You aren't usually strengthening either just the chassis or the receiver, but rather the attachment points and locations. Hope that helps.

Jeff

[zetatre]

Thanks Jeff for your comment: what you say makes lots of sense.

I have an email into CanAm asking about the reinforcement they add to the X5 -> they have a few pix on their FB page, but I couldn't tell where and how it is welded/connected to the unibody.

I believe, just by looking at the picture that it connects to the cross member connecting the two rear mounting points of the rear axle subframe.



In this diagram it would be the orange member in the rear of the car. I'd like to see how.

I'm also interested in seeing pictures of other things that people have done.

If anyone is interested here's a couple of documents about the construction of the E70 chassis with description of the material used.

https://drive.google.com/file/d/0B1e...ew?usp=sharing

https://drive.google.com/file/d/171D...ew?usp=sharing

[Bgibbs]

I owned a BMW repair shop for 40 years and saw any number of X5's that had big repair bills from towing. There is nothing about an X5 that was designed for towing any more than a very small trailer. Towing an Airstream is better handled by a vehicle designed to tow. Another consideration is lack of service facilities in the remote areas that you might plan to visit. I would much rather be towing with a Ford, GM or Ram product if I needed repairs in the mountains of Colorado or most any other scenic part of the country.

Save yourself some misery and get a 3/4 ton domestic pickup.

[zetatre]

Originally Posted by Bgibbs

I owned a BMW repair shop for 40 years and saw any number of X5's that had big repair bills from towing. There is nothing about an X5 that was designed for towing any more than a very small trailer. Towing an Airstream is better handled by a vehicle designed to tow. Another consideration is lack of service facilities in the remote areas that you might plan to visit. I would much rather be towing with a Ford, GM or Ram product if I needed repairs in the mountains of Colorado or most any other scenic part of the country.

Save yourself some misery and get a 3/4 ton domestic pickup.

Give examples...

I can find plenty of trucks with bent frames from towing, but any search of X5 with damages from towing comes up short.

I'm glad I finally found someone with experience: be specific as I know the E70 inside out over and under.

[bono]

Please give the address of the repair shop. There are not many places in the US having experience with repairing BMW with issues resulting from towing.

Originally Posted by Bgibbs

I owned a BMW repair shop for 40 years and saw any number of X5's that had big repair bills from towing. There is nothing about an X5 that was designed for towing any more than a very small trailer. Towing an Airstream is better handled by a vehicle designed to tow. Another consideration is lack of service facilities in the remote areas that you might plan to visit. I would much rather be towing with a Ford, GM or Ram product if I needed repairs in the mountains of Colorado or most any other scenic part of the country.

Save yourself some misery and get a 3/4 ton domestic pickup.

[jcl]

Originally Posted by Bgibbs

I owned a BMW repair shop for 40 years and saw any number of X5's that had big repair bills from towing.

It would be good to see what the failures were in your shop, and how the vehicles were set up.

The only BMWs I saw that had damage from towing were early E53 X5 models that used aftermarket receiver hitches (that didn't include the chassis stiffeners inserted at each mounting location), and aftermarket trailer wiring kits that did not play well with the sophisticated BMW wiring. Both were resolved with using OE accessories.

The rear pan damage documented from the aftermarket hitches was in the 2000-2001 time frame. The various hitch suppliers (Curt, Drawtite, etc) added in a longitudinal strut to compensate for their poor attachment design. It got bad enough that my local UHaul (which had a large hitch installation shop) asked me when I rented a large box trailer what type of hitch and wiring I had on my E53. I responded OE, and that it worked fine. They were satisfied; they had a memo advising them that they were no longer allowed to install hitches and wiring on that model vehicle, due to the money they had had to pay out.

It just comes down to knowing the vehicle. My E53, and my E83, both tow very well. No vehicle damage or problems what so ever, apart from a failed trailer wiring module on the E83. Covered under the accessory parts warranty.

Jeff

[jcl]

This applies to the E53, not the E70 or F15 versions of the X5, but it shows the thought BMW put into designing for towing with this vehicle. This is an OE receiver hitch kit. Installing it requires removing the single-use collapsible struts that the rear bumper is mounted on, and replacing them with rigid reinforcements that are bolted to the rear pan at the pentagonal plates, and to longitudinal sections in the chassis (in two separate planes). A new (heavier) bumper carrier then mounts behind the receiver. Very solid.

For the E70, which doesn't include these struts due to the design differences, the Canam modification essentially does what the BMW E53 design does, which is to spread the load out to the unibody.

Early aftermarket hitches for the E53 attached where those pentagonal plates sit, but without the reinforcement plates, and without the two longitudinal struts. They applied a lever to the rear pan, made worse with the use of cargo carriers and heavy tongue weights. The solution was to use the correct receiver hitch for the application. It didn't need to be installed at a BMW dealer (they freely handed out the installation booklet).

Jeff

[wlanford]

We have a 2015 X5 35d (F15) that we use for towing our Flying Cloud 25FB. We had the hitch installed and reinforced at Can Am last fall. Here a couple of photos of the install.

[zetatre]

Thanks for the pictures!!!

Conceptually it looks very similar to what is done to the E70... I still would like the see where and how is welded to to actual chassis.

But in general looking at these, one question I still have would be the implications in the event of a rear end collision and the likelihood of causing frame damages that would otherwise not occur. Just like this brace transfer the loads of the hitch, it would also transfer the energy of the crash.

I'm not talking about more serious accident that would damage the chassis regardless, but relatively minor rear end collision that could otherwise result in a bent receiver or tow bar, but that with a similar reinforcement could cause damages to the chassis where the reinforcement is welded to.

A bent receiver would be replaced, while a damaged chassis would result almost certainly in a total loss.

But having seen and held the receiver, I'm unsure whether that thing can bent or would just transfer everything to the chassis anyway, which would make my point irrelevant...

Thoughts?

[bono]

Another question is whether to weld this reinforcement to the chassis or to use bolts? The reasons could be an easier access to the muffler (if needs to be be replaced) or taking the reinforcement off before selling the car.

Also, I am wondering is the square tube is necessary or it could be replaced by a flat iron? See a picture of Porsche Cayenne reinforcement done in one of the CA local hitch places - this comes from Knuff, another user of the forum

[jcl]

Originally Posted by zetatre

But having seen and held the receiver, I'm unsure whether that thing can bent or would just transfer everything to the chassis anyway, which would make my point irrelevant...

Thoughts?

If you have no receiver installed, up to a few mph a rear end collision only hurts the bumper.

If you have a receiver installed, and you have a rear end collision over a few mph, the unibody will likely give before the receiver hitch. Over a certain speed, both will be damaged.

If you have a brace installed, I would think that that certain speed would be a few mph faster, but above that you are facing major damage in any case.

So I wouldn't worry about it at all.

I would consider future service access. A bolted connection makes sense.

Jeff

[bono]

Thanks Jeff for your contribution to this thread! What are you thoughts in relation to using a flat iron vs. square tube?

thanks!

[jcl]

I wouldn't use a flat bar myself, because I would rather have the stiffness of a box section. Doesn't have to be square, though. It would depend on the ground clearance required.

Jeff

[wlanford]

Here's a photo of where the Can Am reinforcement attaches to the chassis on our 2015 X5 35d.

[zetatre]

That is quite an interesting, and, I admit, a bit puzzling choice for a mounting location.

Specifically that is the rear suspension carrier



Primarily for reason of noise insulation, the suspension carrier is mounted to chassis via rubber bushings: their purpose is to isolate the road noise which doesn't get transferred to the chassis, thus "the car is more quite". And they achieve that, being rubber, but not being rigid.

Seems counterintuitive...

[Knuff]

We went with the flat iron for reasons of ground clearance and also when thinking about the attachment point and where the weak spots are the flat iron seemed to be more than enough. Also to keep in mind that the reinforcement is mainly meant to redistribute force and not to bear the maximum load. It is an accessory piece. We also decided to use bolts for attaching the reinforcement bar to the crossbar on our Cayenne in case we have to replace the muffler at some point.