Brake controller for E70 experiences

wsanchez · #1 03-08-2008, 12:39 AM

I bought an E70 in January and to tow an Airstream 16' travel trailer which I picked up last week. The process of getting all set up to pull the trailer has been a bit less straightforward than I was hoping...

I got the BMW hitch installed at my dealer. I asked before they installed if it would control the brakes on the trailer and I was told it would. After I got my X5 back, still being told that the brakes thing would be fine, I looked here and got the installation manual, which makes it pretty clear that a brake controller is not part of the install.

My understanding is that the brake controller is a requirement for towing anything of much weight, so being told that it's there and then finding out that it isn't wasn't leaving me impressed.

So I went to a trailer vendor and they were skeptical about dealing with an X5, but poked around a bit and found that (unlike the E53, apparently), there is some useful wiring in the vehicle, so you don't have to tap into the brakes yourself, etc. This was very promising, but the connector is in the wiring compartment in the trunk (right side hatch).

Since the controller needs to be where the driver can reach it, that was not ideal placement. Unless an existing wiring harness runs up to the driver area, they'd have to pull off a lot of plastic to run one up there. Not being BMW folks, they thought that would be best done by BMW.

So I went back to the dealer, a bit grumpy due to feeling misled about the install, confirmed that no such harness exists. They weren't terribly interested in performing a "specialty" (non BMW parts) install, but I insisted that since they sold me a vehicle that claims to tow 6000' and then installing a hitch that claims to tow 6000', that I expect it to do so legally and safely, which means I need a brake controller.

So they agreed to run the wiring up to under the steering wheel, where the friendly trailer folks could install the controller.

At this point, I have a good setup with everything working well, but I just wasn't feeling the BMW love I was expecting after buying a swank ride with all the options, eh?

The upside if you can get the wiring up to the front, the rest is of the controller install is fairly easy.

I also noticed that the sticker that came with the hitch says not to use weight distribution equipment. The trailer came with a weight-distributing hitch, so I asked the trailer folks about it, and they have no clue why BMW would advise against using one; I'm told they reduce sway and are "1000 times safer."

Anyone know why BMW advises against using weight distribution with the E70 OEM hitch?

Karlbalmer · #2 03-23-2008, 08:28 AM

may be that it transfers too much weight to the rear of the veh.

HoustonMtn · #3 04-15-2008, 08:58 AM

A weight distributing hitch transfers weight away from the rear axle. Some is transfered to the front axle of the vehicle and some to the trailer axles. You were told right, wsanchez, they are safer.

I can't pretend to be inside their heads at BMWNA, but here's a theorem: IF they rated it to pull 6K AND the only way to pull a 6K trailer is with brakes, THEN a surge brake equipped trailer is the only option left. This negates the use of a weight distributing hitch. Which seems to be the way they do it in Europe.

Which wire(s) did they have to run up to the front?

Mabuhay · #4 01-08-2009, 03:16 PM

Quote:

Originally Posted by HoustonMtn

A weight distributing hitch transfers weight away from the rear axle. Some is transfered to the front axle of the vehicle and some to the trailer axles. You were told right, wsanchez, they are safer.

I can't pretend to be inside their heads at BMWNA, but here's a theorem: IF they rated it to pull 6K AND the only way to pull a 6K trailer is with brakes, THEN a surge brake equipped trailer is the only option left. This negates the use of a weight distributing hitch. Which seems to be the way they do it in Europe.

Houston, can you explain how a "weight distributing hitch" works? I understand from your description above that it transfers weight AWAY from the rear axle. I assume this means rear axle of the X5 and not the trailer (sorry if dumb question). So I am having a hard time understanding how could a device "transfer" weight. If the weight distribution of our X5 is 50/50. This is telling me that this hitch can make it 60/40 or so? I'm wondering how does it do so mechanically. And why would this be a safer setup?

JCL · #5 01-08-2009, 04:57 PM

If you look at the picture above your post, around the hitch ball, you will see the equalizing bars coming back from the hitch (not the electrical hookups, which are looped in the same location). They are under the trailer A-frame, and are about 3' long. Think of those bars like wheelbarrow handles. If you lift on them, you will raise the back of the vehicle, and transfer load to the front axle. Those bars are lifted by being connected to the front of the trailer, on the A-frame. They can swivel left/right, so the trailer can turn corners. But by tensioning them, pulling them upwards, load is transferred off the rear axle, to both the front axle and the trailer axle.

The X5 doesn't have 50-50 weight distribution except when it is empty. Putting a load in the back of it, or a heavy hitch load on it, changes it towards your 40-60 (F-R) number, although I don't know what the actual distribution would be. A weight distributing hitch helps shift it back closer to 50-50, although you won't likely get right to the empty weight distribution %.

Mabuhay · #6 01-08-2009, 11:20 PM

Quote:

Originally Posted by JCL

If you look at the picture above your post, around the hitch ball, you will see the equalizing bars coming back from the hitch (not the electrical hookups, which are looped in the same location). They are under the trailer A-frame, and are about 3' long. Think of those bars like wheelbarrow handles. If you lift on them, you will raise the back of the vehicle, and transfer load to the front axle. Those bars are lifted by being connected to the front of the trailer, on the A-frame. They can swivel left/right, so the trailer can turn corners. But by tensioning them, pulling them upwards, load is transferred off the rear axle, to both the front axle and the trailer axle.

The X5 doesn't have 50-50 weight distribution except when it is empty. Putting a load in the back of it, or a heavy hitch load on it, changes it towards your 40-60 (F-R) number, although I don't know what the actual distribution would be. A weight distributing hitch helps shift it back closer to 50-50, although you won't likely get right to the empty weight distribution %.

So to check my understanding, the "weight distribution hitch" is made to shift the weight OF THE TRAILER...towards the front axle or rear axle OF THE TRAILER. i.e. - your wheel barrow analogy (which helped a lot, btw if my understanding is now correct).

I think the thing that's been throwing me off is when people refer to "vehicle" vs. "trailer" vs. "X5". For example, Karlbalmer states "may be that it transfers too much weight to the rear of the veh." I guess in this case, "veh." means "trailer".

When Houston says, "A weight distributing hitch transfers weight away from the rear axle. Some is transfered to the front axle of the vehicle and some to the trailer axles. You were told right, wsanchez, they are safer."

I assume he means "A weight distributing hitch transfers weight away from the rear axle OF THE TRAILER. Some is transferred to the front axle OF THE X5 and some to the trailer axles..." So this one doesn't make sense in that how the hell does it transfer weight to the front axle of the X5? Houston...we have a problem... (sorry, I couldn't resist!).

JCL · #7 01-09-2009, 12:19 AM

Quote:

Originally Posted by M3Armand

So to check my understanding, the "weight distribution hitch" is made to shift the weight OF THE TRAILER...towards the front axle or rear axle OF THE TRAILER. i.e. - your wheel barrow analogy (which helped a lot, btw if my understanding is now correct). Correct

I think the thing that's been throwing me off is when people refer to "vehicle" vs. "trailer" vs. "X5". For example, Karlbalmer states "may be that it transfers too much weight to the rear of the veh." I guess in this case, "veh." means "trailer". No, he meant the X5, but he had it backwards

When Houston says, "A weight distributing hitch transfers weight away from the rear axle. Some is transfered to the front axle of the vehicle and some to the trailer axles. You were told right, wsanchez, they are safer." Absolutely correct.

I assume he means "A weight distributing hitch transfers weight away from the rear axle OF THE TRAILER. No, he means the rear axle of the X5 Some is transferred to the front axle OF THE X5 and some to the trailer axles..." So this one doesn't make sense in that how the hell does it transfer weight to the front axle of the X5? By lifting the back of the X5, applying a torque load that pushes down on the front axle of the X5 and pulls up on the rear axle of the X5. Houston...we have a problem... (sorry, I couldn't resist!).

The thing to remember is that you can't believe everything you read on the internet. You mistakenly assumed that every post was logical.

Mabuhay · #8 04-27-2008, 08:30 PM

Bump - any new news on this? Since I am in the market for a trailer to pull my M3 + trailer = 4500 lbs, I need this info as well.

So from what I read, I gather the following:
1) BMW claims our X5 can tow 6000 lbs.
2) We need to have a "brake controller" to legally tow a large amount of weight.
3) The X5 is not "pre-wired" to have a brake controller and we would have to spend extra to have someone install wires to the driver side area in order for an after market brake controller to be installed.
4) BMW's trailer instructions states "Do not use weight distribution equipment" yet doing so is probably MUCH safer. What gives?

JCL · #9 04-27-2008, 10:31 PM

Quote:

Originally Posted by M3Armand

Bump - any new news on this? Since I am in the market for a trailer to pull my M3 + trailer = 4500 lbs, I need this info as well.

So from what I read, I gather the following:
1) BMW claims our X5 can tow 6000 lbs.
2) We need to have a "brake controller" to legally tow a large amount of weight.
3) The X5 is not "pre-wired" to have a brake controller and we would have to spend extra to have someone install wires to the driver side area in order for an after market brake controller to be installed.
4) BMW's trailer instructions states "Do not use weight distribution equipment" yet doing so is probably MUCH safer. What gives?

No new news, but here is the summary:

1) Yes
2) Not just legally, but safely, which is more important, unless you use surge brakes.
3) Correct, if you use an electric brake controller and not surge brakes.
4) Correct, if you tow heavy weights, ie 6000 lbs plus. Not really necessary for 5000 lbs, but not a bad idea. YMMV. What gives is that BMW is in the SUV business, not the towing business.

wsanchez · #10 09-16-2008, 03:14 PM

HoustonMtn, M3Armand:

The E70 is technically pre-wired for a brake controller.

The problem is that the connector is in the rear compartment in the panel on the right side, and the brake controller needs to be where the driver can reach it (front left). That means I had to run a wire bundle from under the steering wheel (where I put my controller) to the connector in the panel in the back.

This is an improvement over the E53, where, I'm told, one has to run wiring down to the trailer connector itself, which is more work.

An update on my situation: I've towed our 16' Airstream (3,500 Lb. GVWR) a couple of times now from San Francisco to Reno (over the Sierras) using the weight distributing hitch that I got with the trailer, and it's great. I've never noticed any sway, and I've never felt like the X5 was working very hard to pull the trailer. Granted, it's not a very heavy trailer, but it's easy to forget it's back there until you look in the mirror.