Living where I do, one often has use for a trailer hitch to tow a trailer or caravan. Limited luggage space and long distances often means having to move furniture and such. Many places offer free loan of a trailer to get your shopping home.

After searching about eBay and other sources I decided to buy a brand new trailer hitch kit from Rameder in Germany. I don't live in Germany, but within the EU so they offered to ship it to me. Their service is above and beyond so I really do recommend them if you live within the EU. You could pick up a used hitch on eBay for less money, but putting a few euros extra into the game you get a brand new with all the fittings needed. I found this worth the extra money.

fThe trailer hitch can be ordered with or without the electrical wiring kit. I want the original BMW wiring and modules to get check control functions on the trailer bulb as well. But for now I'm going to use the aftermarket kit which supports CC systems. Though you do NOT get the instrument cluster warning you get a buzzer that lets you know if a bulb is out. Also I ordered the complete kit to get brand new wiring to the hitch, which I'll adapt to use with the original BMW trailer modules when I find them on eBay.

The kits consists of the following items:

• Trailer hitch bar
• The hitch / ball
• Trailer electrical connector mounting plate
• 2 bars for reinforcement
• All bolts and nuts needed

The electrical kit consists of:

• Wire harness
• Trailer module
• Buzzer module
• Trailer electrical connector

The wiring kit is of good quality which is made to fit nicely into the vehicle. The only downside is that you will need to cut and splice into the original wire harness. The E34 kit is better since it just plugs into the various connectors instead. All wires are in rubber tubing and comes with a trunk floor pass-through rubber booth as well. Trailer electrical connector ends come with reinforcements too.

Overall the kit is very good. I believe this is the same kit you actually did get on your vehicle when new. Except for the wiring kit that is. All is made by Brink.

Mounting

Takes about 2-3 hours to complete depending on working conditions and tools available.

Note! This is a job for two persons!

Remove rear bumper by carefully depressing 4 tabs in the chrome (unless your vehicle is a Shadow Line edition) bumper top strip. You can see these if you look closely. Also pulling back the strip a bit will reveal them better. Doing one tab at a time you depress it with a flat screwdriver (take care not to chip the chrome or paint - I used a bit of tape to protect the strip). Pull it a bit back and then work your way to the next tab until all tabs are released. Carefully pull the strip backwards.

Now you'll either have revealed two Torx 55 or Hex bolts that hold the bumper onto the vehicle. Unbolt these and remove the bolts. These were not very tightly mounted on my vehicle so they should be easy to remove.

Before pulling the bumper work on the rear inner wheel arch protections. These will need to be carefully pried out so that they rest on the outside of the bumper instead of inside the bumper. Otherwise you'll have problems removing the bumper. These can be tricky as they're of hard plastic.

Do NOT forcefully pull out on the bumper sides as you will break the bumper mountings.

When the inner wheel arch protections are freed from the bumper, pull the bumper backwards. Here's where you want to be two persons so that you can pull straight without damaging the bumper mountings. Note the bumper is heavy! Also take care to retain the rubber gasket around the entire top of the bumper.

Here's a very good illustrated article on bumper removal.

Place bumper in a safe place.

The trailer bar mounts using 6 hex bolts into the frame of the vehicle. The holes are already present but they may be filled with dirt and grime. Working under the car clean the two holes on each side of the vehicle, plus the two near the center of the vehicle. There seems to be some kind of glue/protection always near one of two of the holes near the exhaust so you will need to carefully clean this away so that the bolts will fit. Make sure the bolts will fit nicely before you attach the trailer bar to the vehicle. This will save you a lot of work!

Place the trailer bar (two persons again) to the car. You can let it rest carefully on the exhaust while you mount the right side bolts. Let them be finger loose as you will need to adjust the bar when you start with the left side bolts. When all bolts are in place, tighten up to the correct force.

Follow the instructions that came with the trailer bar.

Trailer bar attached to vehicle

Remove the trunk carpets and trunk rear panel (that covers jack etc).

Remove the right trunk floor plug right to the spare wheel. Feed the wire kit into this hole until you can pry it out the center hole above the trailer bar. Mount the rubber booth properly.

Connect the trailer electrical connector to the wires.

Only one wire strand goes to the right side of the vehicle rear lamp assembly. The rest all is routed to the left side. I used the original wire straps found behind the jack cover and made it all look very nice and tidy.

Below you can see the two modules, the left side light connector wiring including battery power source wiring (red and red/yellow) with the brown grounding wires in the background. Finally the grey and grey/white wiring for the left side foglight is also shown. 

Below is the right side tail light wiring harness which just has 3 wires since it doesn't tap into the rear foglight on that side. Speaking of which, I've drawn a single wire from the left foglight over to the right one but haven't connected it yet since I am not sure if that circuit will handle the load. An update will follow here as soon as I figure it out. This means I have just a left rear foglight at the moment.

You will now need to drill 6 holes from the trunk through the trunk floor for the reinforcement bars. Measure up the correct placement and drill these 8mm holes. Remove any metal debris and apply anti-corrision paste to the holes. Bolt the reinforcements in place.

 
3 holes drilled to match trailer bar below. Right picture shows reinforcement laid in place.
Note the plastic plug. There's a similar one to the right of the spare wheel where the cables are fed through.

You will now need to cut an opening in your rear bumper so that the trailer hitch can protrude. The opening need to be at least 10 cm wide (4 inches). It should be a bit more to the right if you decide to have the electrical connector on the right of the hitch, or more to the left if you decide to have the electrical connector on the left of the hitch. Here's a few tips to help you cut the right opening.

When looking at the bumpers inside (place it upside down while performing these steps), you will want to cut an opening in the center between the exhaust curvage and the right end of the bumper. You'll see a space that seems to be made for the trailer hitch opening, which it is if you have the original hitch mounted. In this area there's a marking of an oval that indicates the center of the square. Note this applies to connector mounted to the right of the trailer hitch. Measure about 5 cm each way from the center (2 inches) and cut all the way from the bottom of the bumper up to just under the bumper center

< will provide picture here later to illustrate better >

Note! Please make sure you have the trailer electrical connector is wired up at this point, and connected to the bracket. The bracket and hitch must NOT be mounted onto the trailer bar yet.

Place the bumper back on the car. Make sure you slide it into the side tracks on both sides and that the rubber gasket is in place. Replace it if needed. Applying some grease to these can help. Also make sure you get the trailer electrical connector through the opening before you slide the bumper fully in place. Before you bolt the bumper in place bolt on the trailer hitch and electrical connector bracket.

Bolt bumper in place and replace the chrome strip.

Electrical wiring is to be performed as per your instructions for your kit.

It requires that you cut the wires to the following rear lamps:

You will also need to tap into the following wiring:

 I always solder connections to make sure they are durable. You may want to use the supplied splice and tap pieces if you feel that's adequate.

Left side soldering in progress. Foglight done and turn signals in the works.