MALE NARRATOR: Besides the driver who just passed you, what else can you lose a race to?
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: Fading brakes.
RACE CAR DRIVER: I got no brakes to slow down.
DIANDRA LESLIE-PELECKY: A race car slipping up the track, a blown engine.
It might not seem as though these events have anything in common, but they do. They're all a consequence of
friction. Friction is the best friend and the worst enemy of race cars. For example, friction between the brake
pads and the brake rotors is what stops a race car. So you might think more friction is better.
JOHN PROBST: When you push on the pedal, that creates pressure in the line, which pushes basically
your brake pad into your rotor.
OSH BROWNE: It creates a lot of friction, and that slows the car down.
JIM KONTJE: When the brake pad compresses against the disk, it's just like rubbing your hands together.
It creates friction, which creates temperature. If you could rub your hands together very hard, the more you do it,
the faster you do it, the more heat you'll create.
DIANDRA LESLIE-PELECKY: Heat is an unavoidable consequence of friction. When brakes get too hot
or fade, they don't grip as well. That's especially a problem at short tracks, like Martinsville,
where the drivers use the brakes a lot.
OHN PROBST : Some of the short track brake rotors will see 13-hundred degrees. And a lot of times you can
actually overcook, if you will, the brake pad itself so it's frictional properties are compromised.
STEVE LETARTE: We run different compound pads at the short tracks, and try to increase that grip.
But eventually, you know, if anyone understands hydraulics, when you get the brake fluid hot enough, when the pad gets
hot enough, when the rotor gets hot enough, it just, the coefficient goes down to such a point where
your stopping power is really limited.
JOHN PROBST: The temperature at Martinsville is a critical element from the point that they exit the corner,
until they enter in turn one or three, is five seconds. They're on the brake for a very long period of
time as compared to other tracks.
DIANDRA LESLIE-PELECKY: At some tracks the brake rotors get so hot that you can actually see them glow.
During practice, teams monitor the brake rotors using temperature-sensitive paint. When the paint reaches a
certain temperature, it oxidizes. Oxidation changes the paint's color, just like iron changes from
silver to reddish-brown when it rusts.
STEVE LETARTE: There's a green that will oxidize at white at about 800 degrees Fahrenheit. You've got
the orange that is still intact, hasn't oxidized so it's not reached 1,000 degrees temperature. And the red is obviously
untouched as well and that's at 1,200 degrees.
DIANDRA LESLIE-PELECKY: The brakes aren't the only part of the car that use friction to do their job.
Tires get their grip from friction as well. The more friction, the more grip. But that means the more grip, the more heat.
LISA SMOKSTAD: The tire on a race track condition, like under a full race run, will run anywhere from
300 to you hope not 350 degrees. Optimum temperature I think that we're looking for is around 320 degrees, 300 degrees.
DIANDRA LESLIE-PELECKY: The problem with that is that a hot tire doesn't have as much grip.
BRIAN VICKERS: From a driving standpoint, you can feel the tires get slicker and slicker and slicker,
and they start to lose grip, you know, and lose the ability to adhere to the racetrack.
DIANDRA LESLIE-PELECKY: There's no way to prevent friction from creating heat. So the only option is to
dissipate that heat as quickly as possible. For example, ducting runs from the openings in the front of the car,
and continuously brings air back to the brakes.
BRIAN VICKERS: You can't use any more than three three-inch diameter hoses. So you have to best be able to
come up with the relative components that cool it, that NASCAR mandates.
DIANDRA LESLIE-PELECKY: One reason racing tires are wider than passenger car tires is because the additional area helps
dissipate heat better. Now, friction is necessary for the brakes and tires to work. But in the engine, friction is never good.
That's because every bit of energy used in overcoming friction, is energy that isn't being used to make the car go faster.
But in the engine, you have an option you can't use on tires or brakes.
ANDY RANDOLPH: Well oil's our friend. I get reminded of that quite often. You need to have oil between
the piston and the bore, and between the rings and the bore, to lubricate that interface. Another thing that you'll also do
sometimes is you'll use bore materials or ring materials that have silicone embedded in the steel or in the iron.
Once again, trying to get a little bit of lubrication there. Cuz if you don't have that lubrication, you're gonna
have high friction, you're gonna generate heat, and you're gonna have failure.
DIANDRA LESLIE-PELECKY: The piston moving up and down creates friction between the piston ring and the
cylinder wall. Without oil to minimize the friction and decrease heat, the engine pieces can actually weld
themselves together.
ANDY RANDOLPH: Any kind of a failure between the piston and the piston rings or the bore is what we
call a catastrophic failure. Which means, if you're watching a race and you see large quantities of smoke coming
out the tailpipes, there's oil, there's water, there's fuel, there's all sorts of bad things that start flying
out the exhaust that aren't supposed to be there.
DIANDRA LESLIE-PELECKY: Friction always creates heat. The key for the race team is managing the heat so that
there's a balance between speed and making sure the equipment lasts the whole race.
After all, no one wants to lose a race to friction.