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      08-20-2011, 12:35 PM   #1
cgroppi
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Custom Z4M Hitch

I've had several people ask about the custom hitch I had made for my Z4MC. I took several pictures today so you can see how it was done. You should be able to get a good custom hitch place to copy this design.

The hitch was made by B&M Bumper and Hitch in Phoenix, AZ. I brought the car to them and left it for 5 days for them to design, fabricate and install the hitch and the wiring harness. The cost was $600 plus tax.

I use the hitch to tow everyone's favorite Harbor Freight trailer mounted with a storage tub for tools and a platform for my Hoosier A6s.

The hitch attaches at the rear to the tension rod mounting bolts (the rear jacking point), and at the front to the bumper beam. Two holes are drilled in the bumper beam, but otherwise there are no modifications to the car structure. I cut a hole in the plastic cover between the mufflers to access the hitch pin and the safety chain loops. The hitch receiver is located behind the lower slot in the rear bumper cover, with a small square hole cut through the plastic mesh. When the hitch is not installed in the receiver, the setup is almost invisible. People usually have to search for a while after I tell them I have a hitch.

The wiring harness is spliced into the right rear taillight wiring in the trunk. When using the trailer, I attach the harness to the trailer, and close the trunk onto the cable.

The attached pictures should do a pretty good job at showing how the setup looks.
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      08-21-2011, 07:42 AM   #2
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NOW, I have a guide to use. Thank you big time.

I just could not visualize how to mount a hitch when the carbon canisters were in the center.

Picture no. four is really what I needed.
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      08-21-2011, 09:15 AM   #3
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Now the decision I have to make... Do it or not to do it?
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      08-21-2011, 09:25 AM   #4
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I already have made the decision. It won't be accomplished until Nov, but I will get it done.

Now a question:
The two bolts in the center of the picture? What do they do? They don't look like vehicle structure mounting?
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      08-21-2011, 07:26 PM   #5
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great post, thanks for sharing with us!
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      08-21-2011, 08:20 PM   #6
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Quote:
Originally Posted by Shipkiller View Post
I already have made the decision. It won't be accomplished until Nov, but I will get it done.

Now a question:
The two bolts in the center of the picture? What do they do? They don't look like vehicle structure mounting?
That's part of the hitch. I didn't see the hitch before it was installed, so I'm not exactly sure what the big one to the left does. I think it is there to hold the hitch together while they welded it. The small bolt to the right is a stop to keep you from shoving the hitch into the receiver too far.
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      08-22-2011, 06:55 AM   #7
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Quote:
Originally Posted by cgroppi View Post
That's part of the hitch. I didn't see the hitch before it was installed, so I'm not exactly sure what the big one to the left does. I think it is there to hold the hitch together while they welded it. The small bolt to the right is a stop to keep you from shoving the hitch into the receiver too far.
That's what I figured but just wanted to be sure.
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      08-23-2011, 01:20 PM   #8
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Very nice.

That looks like some great engineering. Is there any way to clip that plastic honeycomb piece in the rear valance in and out, so it doesn't need to be cut out in the middle?
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      08-23-2011, 04:28 PM   #9
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Quote:
Originally Posted by DR Z4 View Post
Very nice.

That looks like some great engineering. Is there any way to clip that plastic honeycomb piece in the rear valance in and out, so it doesn't need to be cut out in the middle?
I'm sure you could, but I didn't bother. If I had wanted to, I would have kept the piece of mesh and attached it to the end of a piece of square channel stock I could insert into the hitch when not in use.
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      08-23-2011, 04:58 PM   #10
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Black rubber/plastic hitch plug.... I know I have seen them.
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      08-23-2011, 06:30 PM   #11
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That's a good suggestion! Do you have a contact person I should speak to at the shop that made this for you?

Thanks.
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      08-23-2011, 09:36 PM   #12
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Quote:
Originally Posted by DR Z4 View Post
That's a good suggestion! Do you have a contact person I should speak to at the shop that made this for you?

Thanks.
I don't remember, unfortunately. It was about a 18 months ago. Their website is:

http://www.bmbumper.com/

I got mine made at their Glendale location.

I doubt they made drawings, so I would suspect they would be unable to copy the hitch without getting mine back. If enough people were interested, and willing to pay a bit for my time, I would consider bringing my car back so they could make copies to ship. You'd then have to get someone to mount it, and there would be the risk of fit issues. It might just be easier to show the pictures to your local custom hitch place and ask them to make something similar (but not necessarily identical).
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      05-01-2013, 01:00 PM   #13
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Trailer hitch wiring

I am thinking of building a custom hitch for our Z4. I'm a certified welder and done lots of fabbing so I'm not worried about the mechanics of the hitch, I more concerned about not screwing up the Z's electrical system with the extra load of the trailer lights. What sort of electrical isolation module did you use? I suspect one would want a unit that takes power from the battery. Could you provide a make and model number of the one you used? Have you had any issues or concerns with the electrical connections? Thanks!
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      05-01-2013, 01:17 PM   #14
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Quote:
Originally Posted by johnw10257 View Post
I am thinking of building a custom hitch for our Z4. I'm a certified welder and done lots of fabbing so I'm not worried about the mechanics of the hitch, I more concerned about not screwing up the Z's electrical system with the extra load of the trailer lights. What sort of electrical isolation module did you use? I suspect one would want a unit that takes power from the battery. Could you provide a make and model number of the one you used? Have you had any issues or concerns with the electrical connections? Thanks!
I'm not sure. I can look and see what model it was. The hitch place did all the wiring for the electrical too. They patched into the right rear tail light wiring. I've had no problems other than the fact the trim piece in the trunk doesn't fit right anymore because of the wiring.
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      05-16-2013, 08:54 AM   #15
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I'm having a hitch fabricated/installed now and will do my own wiring. I plan on getting a powered converter like this. It uses the signal from your taillights, but draws power directly from the battery. This type of converter seems to be the best solution.
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