Originally posted by Flyboy Dave
That's the speed at which the guy next to you...has to wear hearing protection, from the sound of your knees banging together.
Whip-lash and Dust flyers usually wear knee pads under their trousers...so as to keep the "banging" under 98 db., and causing hearing loss. 
Hey Dave! That's how I tune my engine..when my knees knock in rhythym with my engine, I know it's set! LOL