iRacing is a simulation of track based motorsports and requires a iRacing.com membership.
As far as racing simulators go, you would be hard to beat iRacing's quality of graphics and realism. It covers all aspects of professional racing including car choice and precision tuning.
The league system imitates the real world racing scene, after entering a game you have to qualify, and you can climb up the global ladder as your skills and racing ability improve.
Strict adherence to the operating rules and rules of race behaviour are insisted upon, anyone purposely causing mayhem or driving irresponsibly during a race will receive a warning or be banned from play.
To see the quality of graphics and immersive realism for yourself, take a look at the videos below.
Credit to 'Dave Cam' an i-Racing user from Youtube who gave me his permission for use. Dave has many videos on Youtube demonstrating and discussing many aspects of car racing.
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