Trailer brakes/towing questions
 

Hi all, I've searched and read all existing posts that I can find regarding towing, and still have a question on the trailer brakes. I'm in the market for an '08 3.0 to replace our '02 3.0, but will want to tow a small ski boat with this one. It seems that I will be able to tow around 3000lbs just fine, and it sounds like the BMW tow hitch is the way to go, although I don't know if it makes a difference if it's installed by BMW or not, as long as it's done correctly. I will mostly be towing short distances, but occasionally will want to take the boat over mountain passes for vacations.

My concern is braking, since the vehicle braking is only rated at around 1600lbs max tow weight with an unbraked trailer. Some previous posts referenced a factory harness that could be connected to trailer brakes, does anyone have any first hand experience towing connected to the trailer brakes this way. When towing and connected this way, does it feed some type of info to the ECU? Is this mis-information, or did I possibly read this incorrectly? I would like to purchase a trailer with the trailer brakes to be safe, but don't want something wired insufficiently or incorrectly. I would like the whole install to be very clean.

Thanks!

That size of trailer will tow very well with a 3.0. I agree that the OE BMW hitch is the way to go. It does not need to be installed by a BMW dealer, but once it is installed coding will be required. That is simply to change a setting in the vehicle so that it recognizes the towing wiring module. That coding will require the dealer, or a shop with specialized tooling. I would get it installed elsewhere, and get the dealer to do the coding, unless the dealer is competitively priced. They usually aren't.

By way of background, there are two types of trailer brakes. Surge brakes have a mechanical application trigger built into the trailer hitch (on the trailer side, not the vehicle side). They work automatically, and no vehicle modifications are required. When the truck slows, the trailer coupling pushes back on the trailer brake trigger. They are not legal in all jurisdictions. They work fine IMO. The second type of trailer brakes are electrically applied. They are controlled by an electric trailer brake controller, which you need to purchase separately from the hitch kit. The controller has two ways of applying the brakes. The first is that when you put your foot on the brakes, the brake lights come on, and that circuit triggers the controller to apply the trailer brakes. The controller is connected to the Lighting Control Module, which controls the brake lights, to accomplish this. The second way is via a manual control that lets the driver apply the trailer brakes separately from the vehicle brakes. In both cases, the controller takes the signal, and feeds electrical power to the trailer brakes to apply them.

You can achieve a clean and safe install with either method. You will likely find that your BMW dealer knows little about trailer brakes; the experts are usually at trailer supply stores, not dealers. BMW has come out with a trailer brake controller for the E70, so it is easier than it used to be. Still, satisfy yourself that they have done the job before.

With that background, the many posts on trailers and trailer brakes may make a little more sense.

Jeff

Thanks for the great info. I didn't realize that BMW has a trailer brake controller for the E70, seems like that would make for a very clean install. Time to go search the "how to's" for that install!

Thanks again, great help.

If you buy the BMW controller (which is rebranded, they don't make them) it plugs right in. Early hitch instructions for the E70 say that BMW doesn't have a trailer brake controller. That was true at the time. When the controller came out it was advertised as being suitable back to start of production in 2007.

Install instructions attached below, with part numbers.

The alternative is to buy a Tekonsha Prodigy, P3, or whichever model you choose.

Instructions courtesy X5Meister, from this classic thead:

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

Jeff

I used the Tekonsha Prodigy RF on my 2011. No under dash wiring necessary – utilizes wireless communication. Works like a charm.

I debated wiring in the regular Prodigy I had but decided to go path of least resistance. The OEM controller as mentioned above is a good option but you give up a cup holder (drivers side) in the process.

1. The BMW hitch and BMW wiring harness is fine.

2. Agree with JCL that BMW dealers know jack squat about trailers and braking.

3. Disagree that the BMW 'brake controller' is worth buying and installing... as far as I know, the car is NOT prewired for this and you'll spend a bunch of money hacking this into place. (I'd wire it under the dash, not a cup holder- and Tekonsha makes a clip in mount that you can use instead of that cup holder/garbage trap they include...)

4. The Tekonsha RF is a sweet unit- the control of the brakes is all done via wired connections at the rear of the car, it is just the user interface that is controlled via the RF (think about it, you don't ever 'adjust' anything while you are braking)

5. The BMW Controller is actually a Tekonsha (Prodigy?)...

No first had experience with eh X5, but tow lots of stuff (14k pound gooseneck, bumper pull stuff, cement wagons, cars, etc) with a tekonsha prodigy.

I believe the BMW rebranded unit is a Prodigy. The only advantage to it is that the harness is prewired for it in the back. If it was a significantly different price then I would buy a Prodigy and figure out where the four wires that BMW supply went to. Agree that it isn't prewired to the front in any case. Same as Ard, I wouldn't put it in a cupholder, but rather under the dash.

I've never used the wireless version, but it looks good.

X5 does just fine towing! My boat trailer uses surge brakes, the actuator is made by tie down engineering, which controls disc brakes on all 4 wheels. No problems stopping with it

Hmmmm, after reading all your posts I am honestly thinking that surge brakes may be the way to go for my application. I am only going to be towing an 18ft Sea Ray, around 3000lbs loaded with the trailer, the reviews I've read on surge brakes seem to be really favorable overall. Do surge brakes have any glaring limitations compared to electronic trailer brakes that I've missed? Are they less reliable under sustained braking conditions like coming down a mountain pass or an extended decent? I am a gadget guy and an electronics buff, but it seems like a BMW hitch with surge brakes on the trailer would be a simple, and most importantly to me, safe set up for my situation. Thoughts?

^^ The chief advantage of electric brakes is that you can activate them remotely to control trailer sway. I towed my boat to Crystal Beach on Lake Erie about 200 KM (120 miles) away from where I live at highway speeds up to 120 km/hr and I never experienced any trailer sway. The surge brakes work just fine.

With surge brakes you have no braking when backing down a ramp. You lose ability to control them from your car too as mentioned.

My preference was to retrofit my Four Winns 2 wheel trailer with electric and I've had them on for 8 years now and easy to maintain and I think better overall control.

As a rule (and I suggest you back this up with 30 minutes reading the results of a google search) Surge brakes will not give you the same level of control and fine tuning as a Proportional Electronic brake controller.

The new tekonshas have a built in accelerometer that allows you to adjust how much brake to apply in relation to the trailer load. How much to apply initially, in response to just touching the pedal- and how much to add in response to the deceleration of the tow vehicle. This adds up to a smoother ride and less stress on the tow vehicle and tow hitch. And better stability.

Are surge brakes "Okay"? Will they "work"?? Of course, millions tow with them. However for the $200-300 it costs to toss on an EBC, I don't know why one would not....

Good info guys, thank you. The lack of braking when backing down the ramp, as well as the ability to fine tune the level of braking are things I hadn't considered. I like the idea of the wireless EBC, I'm just trying to figure out the logistics of wiring and mounting. I agree that the additional cost is not much for the higher level of safety and stablity the EBC provides. It's just a bummer that BMW doesn't offer much support for those of us that want to tow. Seems like it could be a lot easier to add the hitch and EBC from the factory.

I agree with bluedragon (I never had sway issues as long as I had the proper trailer tongue load), 4MoJoe (no trailer brakes when backing down a ramp can be an issue at low tide), and ard (electronic brakes are more sophisticated).

My towing has ranged from no brakes (including my own vehicles and driving a tow truck), to surge brakes, to electric brakes, to air brake equipped vehicles (class 8 trucks).

Two points:

1) All that control presumes that the operator knows how to use it to full advantage. Applying too much or too little trailer braking removes all the advantages of an electric brake controller. Surge brakes win for simplicity. They are automatically proportional, the harder you brake the harder they are applied on the trailer.

2) It is more important IMO to maintain your braking system that it is to pick one over the other. Many trailer brakes don't work due to corrosion and lack of maintenance.

Personally, by the time I got to 5000 or 6000 lbs, I would choose electric trailer brakes. At 3000 lbs I would choose surge brakes, unless I suspected that as a boater I was subject to two-foot-itis, implying that the next boat would come in above 3000 lbs.

BMW's lack of support for towing isn't surprising. It is the same for all auto manufacturers. When you get to heavy duty pickups, you can get built-in brake controllers. But not on cars. It is actually quite a bit better than it used to be with the X5, as there was no BMW brake controller option and no prewiring for the brake controller until the last two years.

I tow a 21 foot Chris Craft. Weighs in at about 3800 pounds including trailer. Trailer has surge brakes. I have had no problems with them at all






http://img713.imageshack.us/img713/5360/img1510qr.jpg

What year/engine do you have? Ever find the surge brakes insufficient on steep boat ramps?

I see your point about the user controlling electronic trailer brakes and the issues that this could cause with inexperience.

The weight I'll be towing seems to be on the low end from what others are saying, and it seems like surge brakes would suffice.

2011 35 Diesel. The surge brakes do not work when you reverse.

The energy required to stop your X5 + 3k lbs boat slowly backing down a boat ramp is considerably less than stopping your X5 from 60 - 0 (kph or mph). It's minuscule if one believes that kinetic energy = 1/2 * mass of the vehicle * velocity * velocity. I'll leave the actual math to JCL! :D

Yeah, a slippery boat ramp is a challenge, but I'm gonna bet that the two little, rock hard 215/75/15 trailer tires won't have that great of an effect anyway vs. your 4 monster sticky tires on the X5. YMMV.

If you don't want to comply with the laws of physics, then nevermind... :thumbup:

Well, if you need trailer brakes to stop when reversing down a boat launch ramp, because your vehicle wheels have insufficient traction, then consider what happens after you stop. You try to drive back up the ramp. And since you have no traction on your vehicle wheels, you need a front-mounted winch with a snatch block and a convenient anchor point just to get back to solid ground. At least that is how we did it back in the F-350 days.

No math required :D

^^ I have to say I haven't had any braking issues backing down a ramp with surge brakes on the trailer, even with 6k lbs of boat and trailer behind me.

Here's a funny story->

I took my boat to get winterized yesterday, the mechanic sees the x5 towing the boat and says, thats an awfully small car to be towing that boat. :rofl: I tell him its 1) diesel and tows easily, 2) has the self levelling rear suspension 3) stops just fine. I took him for a short drive after the work was done, and he was sold. He couldn't believe it towed so easily.

I have a 2012 X5 35i with the turbo inline 6 gas. I tow a 23' Sea Doo Challenger 230SE jet boat 30 min each way to the lake with highways, which means on/off ramps and inclines/declines.

The trailer is a two axle trailer that I believe is 26 feet in length with surge brakes. I've never had the slightest problem and I was extremely suprised the gas engine tows the boat so easily. It weighs roughly 5,500 lbs with gas and supplies. The engine never has to work hard and gets up to speed easily on the highway. The surge brakes work flawlessly and I never feel like the BMW has to work that much harder than normal.

Just use common sense and give yourself more room to brake and be safe. Don't be in a hurry. The X5 has built in trailer sway control that doesn't need to use the trailer's brakes to control sway. I had read somewhere that surge brakes are more popular on boat trailers as they are submerged often in water.

On a side note, I'm looking at the wireless electronic brake controller to be able to tow a 2 horse trailer that has electronic brakes.