76FJ55

The factory hitch is rated at 75kg (165lbs), so there is that data point.

Jerry Feather

Jeremy posted above that the Factory tongue weight limit was 150 pounds, but that the trailer weight and load limit was 3500 pounds, as I recall. Those numbers do not seem to jive with a 10 to 15 percent tongue weight.

Jerry Feather

OK, 1870 KG and 75 KG results in a 4% tongue weight limit.

hwyengr

There’s a difference between Euro towing standards and US standards. Higher tongue weight provides more trailer stability at higher speed. Most european countries have a strict towing speed limit of 90km/h. American drivers like to tow at 90mph. So the SAE towing standard recommends 10% tongue weight as opposed to the European 5%.

If you tow at 55mph, you can still drop tongue weight to 5% here. The physics are the same.

UKenGB

Seems to me that it makes the most sense to use a standard sized receiver. My vote would be for 2" for 2 reasons:-
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Jerry Feather

What all of this says to me is that even the Factory Hitches are unsuitable for the 928. The reason is that I know from experience that pulling a trailer when the speed limit is 55 mph means nothing since everyone pulling a trailer will still pull it at over 70 mph. Drive around California some and observe for yourself. I think that the tongue limit for the factory hitch is based on what the car will bear and not on the hitch itself. It you are pulling a trailer that weighs say 3500 pounds and you are pulling it at over 55 mph you need tongue weight limited to 350 pounds and that is over twice what I think the car will bear.

I think my hitch would take 150 pounds of tongue weight, and probably more, but the car will not take much over that together with the hitch. This project is snake bit; so I am going to bow out.

76FJ55

I tend to think you're right in the hitch being capable of bearing significantly more than the rates 75kg tounge weight, but I also belive the chassis is likely capable of carrying more as well. In my opinion it is likely limited by the relatively low spring rate of the factory rear coils. Carrying a cantilevered load aft the rear axle transfers quite a bit of load onto those soft rear springs and will squat the rear suspension leaving little bump travel.