The rule I use is that a helmet is cheap insurance for your head, my wife flipped a pro mod on an 1/8th mile track and still has the time slip where she slid across the finish line on the roof @ 132 MPH and had MY Simpson Voyager helmet on. I had paid close to $400 for the helmet some years ago, the helmet died and she walked away with bumps and bruises everywhere but her on her head. I layed my Harley down doing 30-35 MPH wearing only a $2 dollar doo-rag and road rashed the top of my head real good or bad.....its how much do you want to spend protecting your head?