Suggested nose weight 90kg car only 80kg

My Caravelle handbook sys that I have a 100 kg maximum vertical weight on the tow ball, and that this must not be exceeded.  It also recommends, for best stability, that the caravan nose weight should be very close to the 100 kg maximum, with out going over it.  If anything such a bike rack is fitted between the tow ball and towbar, this and the bikes must be included as part of the nose weight on the tow ball.

Not quite true CY but close enough. The tow car's permitted hitch weight must be at least 4% of the car's maximum specified towing capacity I seem to recall

Correct EasyT. The permitted noseweight must be at least 4% of the car's maximum specified towing capacity, but that doesn't mean that the actual noseweight must be at least 4%.

My vehicle's maximum towing capacity is 2500 kg.  The maximum permitted nose weight on the tow ball is given in the handbook as 100 kg, which just happens to be spot on 4%.  It also recommends towing close to this maximum for stability.

 And 100kg is also probably the max coupling capacity

The S (static load) value of the tow ball on my vehicle is 150 kg.  This value is for certification purposes and the vehicle's specified 100 kg is the legal value, and should not be exceeded.

Which also the legal max load on the coupling head on most c/vans,which comes as a suprise to some when mentioned