Ok, but I'm not English, I'm American, we don't call our car trunks boots, they are trunks;we don't call our car hoods bonnets, they are hoods; we don't call cigarettes fags either; we don't spell tire tyre. So the old saying is that if in Rome do as the Romans do, I'm in America I do as the Americans do thus the wheel spinner is a knock off which is completely 100% correct in America which is where I live and sleep for the last 63, well knocking on 64 years.
I understand some of our words are bit weird, but you then have to listen to the content of the message and it would become apparent rather quickly that it was either a fake or part of wheel...except most people that are under 50 probably would have no idea what the spinner even was regardless if it was called a spinner, knock off, or knock on. But the one thing you missed in the word of knock off was that the word for the spinner is in two parts KNOCK and OFF, the fake word is one word KNOCKOFF, so reading a content will tell you too which one we are talking about.
I don't have any English repair books anymore I left those too with the TR6, but I had to go to a British car sales parts desk and order one once, we both called it a knock off. Again it doesn't matter if a British book calls it a bonnet or a boot because we would simply say a hood or a trunk. The funny thing is with all this twisting word stuff is if someone didn't know in your country that a boot was a trunk they would think your talking about a boot you wear on your feet! If someone came to our country that didn't know what a trunk was they maybe thinking for either a elephant or a suitcase. Bonnet to an American means something women wear on their heads, but hoods are something that both men and women might wear too. In Britain I might go up to someone and say "give me five" and he might punch me, if I did that in America I would get his hand to slap my hand. If I walked into a British store and asked for a rubber they would hand me an eraser, but in America I would get a condom. A trainer here is a physical fitness person who trains others and not a tennis shoe like Britain says. In America a queen is a man dressed and made up to a women, but in England it's a lady who is the Queen of England.
Anyway this sort of thing goes on and on.
But since I am in America I am correct in using the work knock off in America.