I haven't seen
Rush. Heard it's pretty well done.
But seriously there is a lot of really bad racing movies:
Grand Prix
Winning
Days of Thunder
Spinout
About a million really bad lower-budget ones from the 50's, 60's and 70's
and, of course, the infamous
Driven 
There's a very few good ones
Le Mans (of course!)
Disney-Pixar's Cars (Cars 2 is okay, as well)
To Please a Lady (Old Clark Gable movie)
There's some other ones that aren't too bad:
Speed Racer 
The Love Bug (first Herbie movie)
The Green Helmet (Low budget, but pretty good)
The Big Wheel (Old Mickey Rooneymovie)