Member - Phil G (SA) replied:

I've seen this one made by Thule that worked beautifully, but I don't think you'll find anything (legal!) that will hold 4 bikes on the back.
Link here

joff1 replied:

None, including the thule, that I have found want you using it offroad (or on the back of a caravan for that matter)

Rod replied:

I have an Allen 303D rack. Alas, only 3 bikes though

ExplorOz - David & Michelle replied:

Not sure if this helps, but the one pictured on the back of our vehicle (see Bike Carrier article in the link box at the top of this thread) comes in either a 3 or 4 bike option. We have the 3 bike option. This is a few years old now, but is the most rugged thing I've ever seen. It's a Swagman brand, marketed by Rhino Rack. As you can see in the pictures in the article the arm swings down. We also have a swing out wheel carrier but this is in dependant of that. Unfortunately, I have no idea of the current availability of these as they are no longer advertising them with us, and I'm not up to date on the latest but maybe look up the name and see what you can find.

MM