Trust, lies and radio waves: during a race, a crew chief might have to use a variety of motivational techniques to spur a driver toward victory lane. (NASCAR).

The loud voice ringing in a driver's headset can bring a spectrum of messages:

You're the best driver since left Gordon.

Your car is two-tenths faster than the leader.

Hell no, you won't run out of gas. Get up on that freakin' wheel and drive.

The moment a Winston Cup driver flips his ignition clutch or rolls off pit road, the crew chief becomes his lifeline, the primary connection between his hurtling machine and the human components that give it such breathtaking speed.

Over the radio that links him to the driver, the crew chief must be part coach, part drill sergeant, part cheerleader and part analyst. It's a delicate ...