I found "Racing Mad" on YouTube and suspect, like in so many silents, that a portion of the film is missing. This is because there was nothing leading up to where the film began....with Al (Al St. John) and his black co-driver in the middle of a race. The baddie cheats a lot...and Al manages to use a few tricks of his own. It's fast paced and enjoyable...but not much more.
By the way, the black sidekick is a good AND bad thing. It's nice to see the hero with a black friend who seems like a co-equal. BUT, much of the time the camera pans on the guy's expression....as apparently back in 1928 folks thought seeing black men who were afraid was somehow funny...which it wasn't.