I can't believe today is the first I've heard of this movie. It will be a goal of mine to get it this week!
The other truly insane race I believe is the famous Dakar Rally. But more specifically for the guys running it on motorcycles. Not 110% flat out like the TT, but 16 days of life on the line with thousands of things that can go wrong along the way. Like the TT I believe I read (for both events) that loss of life is typical on average each year.
This book was where I learned what Dakar is all about and found it quite shocking.