DRIVER: The car is tight on entry, and loose when I pick up the throttle.
NARRATOR: Listening to a driver on the radio sounds a little like Goldilocks and the Three Bears. The car is either too loose,
or too tight. The key to winning: getting the car just right.
The roar of the engines, the squeal of the tires, then the race to victory lane. It all says, NASCAR. A race car is much more
than steel, gas, rubber and speed. A race car is a science experiment on wheels.
DIANDRA LESLIE-PELECKY: What does it take to win a NASCAR race? The ideal set up, and a driver pushing the car to the
very edge of its limits. But driving on the edge means that a single misstep can take you from a perfectly
balanced car to a pile of scrap metal.
NICK HUGHES: The driver's job really is to drive our cars to the absolute limit. As you approach the limit of the car,
something's gonna hit the limit first. If it's the front end of the car, and the car stops responding to his steering input,
then the car is tight. It basically means the car won't turn any more.
BRANDON THOMAS: You're slowing down, you're making the corner, you're following your arc, and then you basically feel
the front end kind of go numb and start to slide across the track.
BRIAN VICKERS: The rear of the car is gripping really well, and the front's not. So as you turn, it doesn't turn.
You're wanting to go this way, and the front of the car is still going this way.
NICK HUGHES: If the rear of the car reaches the limit first, then the car is loose, and the car will tend to want to spin out.
BRIAN VICKERS: You know, the front's turning but the back's not. So you go in the corner, you're turning left,
and the back's going this way.
DIANDRA LESLIE-PELECKY: When a car hits the wall, you usually can tell whether it was tight or loose
by which end hits the wall first.
NICK HUGHES: I think someone summed it up as, tight is when the front hits first, and loose is when the rear hits first.
DIANDRA LESLIE-PELECKY: The car's weight creates grip by pushing the tires into the track. Adjusting weight
distribution affects the car's front and rear grip.
DIANDRA LESLIE-PELECKY: A crew chief can get a car perfectly balanced in the garage, but nobody comes to the
racetrack to see cars in the garage.
BRANDON THOMAS: Balance is a bit of a fuzzy term that comes from the drivers. Because they're the
only ones that truly know what it is.
BRIAN VICKERS: You know, maybe the balance of the car is right, both ends are gripping equally.
But guys are still faster than you, and you just need more grip.
DIANDRA LESLIE-PELECKY: A driver's lap times at the start of a green flag run are not the same as
his times at end of the run.
JOSH BROWNE: You'll start out, let's say, running 30 second laps for the first ten laps, you'll slow down a second,
so a tenth of a second per lap for the first ten laps.
DIANDRA LESLIE-PELECKY: So why the slow down?
BRANDON THOMAS: We always complain the drivers are getting tired. They say they're not. The biggest thing we see on stock cars
over the course of a green flag run is degradation of the tires.
DIANDRA LESLIE-PELECKY: A tire gets hot the longer it runs. The tire pressure increases and the tread gets worn down.
CHRIS ANDREWS: At Martinsville, for example, a left side tire can start with ten pounds of air pressure in it,
and can finish a hundred-lap run with almost 30 pounds of air pressure in it. Three 30-seconds, four 30-seconds
of tire tread can wear off the surface and go away. And then the tire gets hot, so there's a performance
difference in the heat just from a cold tire to a hot tire.
DIANDRA LESLIE-PELECKY: If that's not enough to worry about, the car is also burning fuel.
BRANDON THOMAS: So from end of a pit stop, leaving pit road, to 90, 95 miles later coming back down pit road.
It's about 125 pounds on the car.
STEVE LETARTE: You know, fuel burn-off, while it seems like it would be a great thing to lose all this weight in a race car,
the problem is it shifts your percentages a tremendous amount.
NICK HUGHES: Because the fuel tanks are located at the rear of the car, as we burn off fuel the car becomes lighter.
But as it burns that mass off, the center of gravity of the car moves forward. As a result, the car will
tend to become tighter as the car will run.
STEVE LETARTE: So we may start with 51 or 52 percent of the weight on the front tires and not so much on the rear.
Over the course of a fuel run, when you burn 100 or 150 pounds of fuel off, that percentage could go up to 56, 57, 58 percent.
Nothing affects a car more than weight percentage of the load on the tires.
DIANDRA LESLIE-PELECKY: A few percent may not sound like a lot, but five percent of the weight of a stock
car is almost 200 pounds of grip.
CHRIS ANDREWS: In Formula One the car gets faster because the tires don't lose grip potential, but they get lighter.
So when they get lighter they get faster. Our cars in theory get faster when they get lighter. But we never find that out
because when we're lighter we're also on older tires. It's very rare that you are low on fuel with brand new tires on the car.
DIANDRA LESLIE-PELECKY: So let's see. The crew chief has to consider tire fall-off, weight distribution and tire loads
and fuel burn-off. We haven't even talked about accidents, rain, dirty air, blown tires or cranky drivers. So the next time
you see a crew chief rummaging around in the pit box for something, it's likely not his calculator.
He's probably looking for an aspirin.