I have never really thought of groups such as the Hell's Angels being a gang. I just always thought of them as a motorcycle group or club. But when you type in motorcycle group you get associations and when you type in motorcycle gangs you get clubs like the Hell's Angels. Interesting. So really what is the difference? They both ride bikes and are a club which you have to join. The difference in a club and an association are dues and amount of loyalty. In a club you earn your patch and in an association you pay dues which pay for your patch. There are also groups of people who ride together and neither a club nor an organization  but if they put a patch with a rocker under it then no matter what they will be called a club.