Is ther such a thing as a chip resistant aerosol spray paint? I want to do some second hand wheels and also so visible areas of my chassis. All the DIY aerosols I have tried have been very soft and/or chip prone. I am looking for black or dark grey not silver by the way.

very soft and/or chip prone is a contadiction in terms, soft paint doesn't chip. There is nothing I know of that fits your bill. The best thing would be 2K single coat but that is pro application only

Best way is to powder coat them. Not as cheap but will last longer. Depends on what your wheels are worth.