The SX challenges are categorised into six different requirements.
These are as follows:
King of Career- Win both the 250SX (East and West) 450SX Championships (Career Mode)
King of the Championships - Reach the podium in 3 Custom 250SX/450SX Championships with Realistic AI difficulty and minimum of 9 Events per Championship (Official Mode)
King of Multiplayer - Reach the podium in 30 Online Single Events.
King of the Tracks – Race 1000 miles (1609km) in any game mode.
King Midas – Earn 10,000,000 (ten million) SX Credits.
Show-off King- Earn 35000 Prestige Points within 5 laps of any track in Time Attack Mode.
To be honest none of these are overly that bad apart from the grind that is ten million SX Credits however, I did find a way to beat one of the SX Challenges almost immediately which is
Show-off King- Earn 35000 Prestige Points within 5= laps of any track in Time Attack Mode.
To do this easy and fast you have two options; simply create a track with a good wide start line and once you have made the track enter into Time Attack mode, to do his from Main Menu go to Single Player- Time Attack-
Before you start though make sure to go to Choose track and pick the track you created. Your other option is to choose a track with sections where there is lots of space to move around – Sam Boyd Las Vegas-Nevada has a good place to do this.
Once in the race simply keep going in circles and earning drift score easiest way to do so is to turn either left or right, lean forward pushing Right Stick up and you want to tap the front brake as accelerating. Do this until you have accumulated enough points at the top middle of your screen and once done complete that lap and quit out.
Please find video below if you need a better explanation, I should also mention that I am using my own track in the video which also explains the need for space being needed.
My track is called Marsupial Cheev, just in case you wanted to use it for this.
The Achievement will unlock in the final rewards screen as it gives you the SX Award. Thank you and enjoy bumping riders of their bikes.