5 to 8 mph seems to be the tolerance for most states.I'm an over the road truck driver so I see A LOT of speed traps and notice when people get pulled over.My truck is governed at 71mph so in most states I'm just legal,but in the states where the limit is 60-65 I can keep it on the floor and never get bothered.It also depends on traffic and whether or not you're on somebody elses bumper when the cop sees you.If you want to TEST your Challenger just find a road somewhere that you're familiar with and know if and where the cops would be sitting,otherwise just set the cruise kick back with the stereo BLASTING and enjoy the ride.