Golden Standard Achievement
Earn 400 gold medals in Career races.
Presuming you start at the beginning and race all available series in order, skipping the bonus races, and either earn gold or restart each race until you do so, when you are done with your 40th Championship Series you will have 373 gold medals (this presumes you skip one of the 10 race championships). At this point you will need to complete any 27 bonus events, of which there are 214 to choose from.
Once you complete the 400th gold medal, this achievement will unlock.