What are the rules on driving with a tow hook in the EU?

Question

I am getting a tow hook installed on my car, the type that you can take off by removing two screws (tools needed). And hence two question:

1. What are the rules in EU governing driving with the hook installed if it is empty?
2. If I am using one of these bike racks mounted on the towing hook, what are the speed limits? Are they the same as for (standalone) cars, or the same as for cars towing caravans?

EDIT: In the near future I am planning to drive through Poland, Czech Republic, Austria, Slovenia, Croatia, Germany and France - so I am mostly interested in these countries.

Answer 1

Partial answer:

I assume you mean a tow hitch normally used for this, instead of an hook for this (because I never heard of bike racks for the latter one).

Germany

The empty hitch: If it obstructs the view to the license plate, it must be removed. There are no other "hard" rules. However, in an accident, if the hitch causes more damage than it would be without, it can influence who pays how much of the whole cost (at least, courts tend to do it like this).

The bike rack: If it blocks the view to the license plate, you'll need a third plate (really a third, not just relocating the existing one). If there is a stricter speed limit depends on the model, there should be some limit in the manuals (at least). If it is not indicated on the rack itself too, take the manual with you.

(source: StVO and FZV, and some statements of lawyers in the internet)

Austria

Same as in Germany
(altough there are red license plates that can be used for the third instead of the normal one, but that's not important for foreigners). (source this time: KFG)