- To lot of non-fans, NASCAR has a reputation
for being low tech and a little bit crude.
And boy, can I relate.
(record needle scratches) (fart squelches)
(ping)
The stereotypical image
that pops into the layman's head when they think of NASCAR,
might not illustrate
the sophistication out there on the track.
To win a NASCAR, the drivers, teams, and engineers,
they need to understand race car physics,
especially aerodynamics.
That understanding has resulted in types of drafting
that don't appear in many other motor sports.
So, today we're going to break down NASCAR drafting,
explain how drivers even use the air itself
against their competition.
Didn't think that we could break down
the science of the shake and bake, did you?
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(ping)
Now, drafting means
using someone else's aerodynamic effect to your benefit.
It's used in all sorts of racing,
even cycling and running,
where you're often see slipstreaming.
That's when someone follows directly behind a competitor
to avoid fighting the wind and to conserve energy.
But in NASCAR, slipstreaming is just the beginning.
Winning drivers need to know multiple drafting techniques
and how to defend against them.
There's the slingshot, the bump-draft,
the two-car tandem, the side-draft,
and even the shake and bake.
These all build off of each other,
and once you know how they work,
watching NASCAR takes on a whole new level.
And they're all based
on just a few fundamentals of race car aerodynamics.
Aerodynamics is about how moving objects
produce changes in the air,
and how changes in the air move objects.
One of the most important concepts
is the pressure differential.
If an object has different air pressure on either side,
that pressure differential exerts force against the object
that moves it towards the area of lower pressure.
The only way to resist that movement
is by applying some other opposing force.
Moving cars create pressure differentials,
which they have to overcome,
and the force needed to do that comes from the engine.
So as the car moves, it pushes air out of the way,
but that air doesn't move instantaneously.
The air gets bunched up or compress in front of the car.
And this creates a high pressure area.
The same movement also creates
a low pressure area behind the car
because it takes time for air
to fill in the space the car has just left.
So you got high pressure in front,
you got low pressure out back,
that is a pressure differential.
Now, to help visualize high and low pressure areas,
I've built me a little wind tunnel.
Now, we have fog that's coming in through this box
and it's filling in through these straws,
it's creating laminar airflow
that's pulled in by a fan here on the back,
and we got a little stocky here
to see where it hits the car.
Now the front, that's the high pressure area.
That's where the front of your car is hitting air,
and it's producing that high pressure pocket.
And in the back, you can see the air is tumbling,
it's falling off, that's the low pressure area.
You can even start seeing it come across the roof line
and get spoiled by the spoiler on the back.
And if you thought,
oh, Jerry built a mini wind tunnel
for just this one demonstration, oh no.
I'm gonna start wind tunnel testing all sorts of items.
We've already put other weird stuff in it like this,
and this, and this, and my personal favorite, this.
(chuckles)
Send me anything,
literally anything, and it'll go in the donut wind tunnel.
Moving into the area of higher pressure
uses power from the engine.
As speed increases, so does the pressure differential
because the car has gotta push more air out of the way.
That means more air resistance or pressure drag,
and even more power to overcome it.
At a certain speed, the car simply doesn't have enough power
to overcome the increased drag,
and it reaches it's aerodynamically-limited,
or drag-limited top speed.
To go as fast as possible,
it seems like you'd want a car that creates almost no drag.
And that's true if you're doing high speed runs
over at Bonneville Salt Flats.
But there's a reason
why many speed record cars end up airborne.
Reducing drag often requires removing downforce.
Downforce is negative lift,
and a race car wing
works like an airplane wing flipped upside down.
It creates high pressure on top and low pressure underneath,
a pressure differential that pushes the car down.
This is what makes a wing different from a spoiler.
Spoilers don't produce negative lift,
they slow the air as it reaches the back of the car.
Now, what wings and spoilers have in common
is that they both change the speed and path of the air,
and the air resist that change
exerting force against the car, or yet more drag.
That means the price of downforce
is increased air resistance and reduced top speed.
But the benefit includes increased grip, cornering speed,
and high speed stability that prevents takeoff
if something upsets the car's balance.
If you're on a racetrack where you have to turn,
a little bit of downforce goes a long way
to improving lap times.
If you wanna know more about race car aerodynamics,
you should check out this episode of bumper to bumper
on the Bugatti Bolide.
And while you're there,
go and click that like and subscribe,
it really helps us out, thank you.
If you've hit your top speed and still wanna go faster,
you can increase power to deal with increased drag.
But race cars, like a NASCAR Cup car
are often already producing as much power as they can.
If they wanna go faster,
the only option is to reduce drag,
and you can do that by changing the car's texture or shape,
essentially making the car more slippery,
so it slides smoothly through the air
instead of trying to muscle air out of its way.
Have you ever tried to muscle air, it's tough.
Muscle the air.
(background laughter)
(ping)
You can see this kind of drag reduction
in cars with active aerodynamics that close off vents,
or lower the rear wing as speeds increase.
But NASCAR doesn't have any of that fancy stuff.
If you're a NASCAR driver and you want less drag,
you have to take advantage
of another car's aerodynamic effect, and that is slipstream.
(engines revving) (upbeat music)
To slipstream, a driver places their car
directly behind another car.
The lead car has to push through the air,
fighting against the high pressure area it's creating,
while the trailing car lets them do most of the work.
The trailing car driver slips along
in the low-pressure stream
left behind the car in front of it.
And that pressure differential draws the car forward.
That's why slipstreaming is sometimes called getting a tow.
The trailing car experiences, less drag,
and needs less power
to maintain the same speed as the front car.
That means in a slipstream,
the trailing car has power to spare,
it could achieve a higher top speed.
But that leaves both drivers with a decision to make.
The trailing driver could stay a few feet back
and just match the front car speed.
One benefit of simply matching speed
is that it conserves fuel.
That can make a huge difference in a long race,
even if it's not especially exciting to watch.
If the lead car
doesn't like doing someone else's aerodynamic work,
it can try to move left or right
to send more air at the trailing car and break the tow.
But the trailing car
can often shadow those moves well enough
to stay in the low pressure wake and catch back up.
But matching speed is a risky strategy
in a race with 40 cars,
because two other drivers might make a different decision
that will make both of their cars go faster.
That's the two-car tandem.
To initiate a tandem, the trailing car uses its extra speed
to get right on the rear bumper of the lead car,
closing the gap.
The rear car no longer has to push any air out of its way,
greatly reducing its drag.
But this also fills in
the low pressure area behind the lead car,
nearly eliminating that source of drag,
and allowing the front car to go faster.
That's one reason why a lead driver
might not wanna break a tow.
Aerodynamically, the two car tandem becomes a single object.
The front car is dealing
with all the high pressure drag in the front,
and the trailing car is dealing
with all the low pressure drag at the back.
This ultimately reduces the total drag on both cars,
allowing both to achieve a higher top speed
as long as they work together.
And there's still one more trick available in the tandem,
and that's the bump-draft.
This is something that the driver of the trailing car
has to decide to do.
The rear car can delicately ram the front car,
pushing up on its rear bumper to speed it up.
This works because
even though both cars are aerodynamically linked,
the trailing car is dealing
with less drag than the lead car,
so it still has power on tap
to achieve a slightly higher top speed.
So by pushing the front car,
the rear car is using this extra power
to increase the speed and tandem, benefiting both cars.
The two-car tandem is used frequently in NASCAR,
even by rivals,
because the speed increase from working together
can be enough to run away from a pack
where everyone is jockeying for position.
But there are downsides for both drivers too.
The driver of a trailing car
in a slipstream or a two-car tandem
has to work harder than the lead driver.
Partially, that's because it's difficult to match speed
and bump-draft carefully.
But the big downside for the rear car,
is that they lose the air that creates downforce,
and this can lead to aero push.
Downforce helps a car maintain grip while turning,
and push is just another term for understeer.
As a two-car tandem goes around a corner,
or even changes its position on the racetrack,
the front car has all of its downforce
available for turning,
but the rear car, it has much less.
The trailing driver has to work harder
to stay directly behind the front car,
'cause if they can't remain centered,
they may break their own tow and lose the slipstream.
And that's when you see everybody go past.
(imitating race car overtaking)
And he's like, " What, don't leave me dad."
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- As long as the front car is relying
on the extra speed they're getting from the tandem,
they may be polite about their turning
to make it easier for the rear car to stay with them.
But NASCAR isn't a contest
to see who can be the best friends,
that's what pickleball is for.
It's a race, and eventually somebody's gonna win.
The front driver in a tandem knows that their trailing car,
isn't just their helpful companion.
That car is also their closest competition.
And eventually, they're gonna try the slingshot.
That's how it is,
your best friends always turn into your best enemies,
life lesson.
They also become your best lover sometimes too. (chuckles)
A trailing car might initiate a tandem
so they can get ahead of the pack.
But if they wanna win,
they're gonna have to get ahead of the lead car too.
On high-speed courses like Talladega,
the slingshot is reserved for the very end of the race.
That's when the trailing car,
instead of using its extra power
to speed up the lead car with a bump,
will dive out from behind the leader and attempt to pass.
They'll have a little speed boost to help initiate the move
and moving out from behind the front car,
recreates that low pressure drag behind it,
further slowing down the front car.
The passing car's speed boost from slipstreaming
may not be quite enough to take the lead
because the car has just exposed itself
to all that high pressure drag it's been hiding
while behind in tandem.
But the passing driver
still has one more trick they can pull off, the side-draft.
Remember that rear spoiler we were talking about,
the one that reduces low pressure drag behind the car,
but also creates a little drag of its own?
Well, if the passing driver can keep the front of their car
close to the other car while they pass,
some of the air that the passing car is displacing
gets dumped up and onto the rear spoiler of the front car,
that creates even more drag,
further slowing the lead car
so the trailing car can complete the pass.
So what do you do if you've been leading a two-car tandem,
your good old buddy behind you
slipstreaming and bump-drafting,
and sacrificing his downforce, dealing with aero push
to get both of you ahead of the pack,
but you wanna avoid the slingshot and the side-draft
to take the win.
Well, you shake and bake baby.
Look, a lot of things will get NASCAR fans,
even drivers, yelling shake and bake.
A reference to the film in Talladega Nights.
Now, the shake and bake in the film Talladega Nights
is really the slingshot.
The real shake and bake happened in 2012,
with Brad Keselowski, and Kyle Busch.
Drivers Brad Keselowski, and Kyle Bush
used every technique here,
and Keselowski took the win
by doing something nobody had seen before.
The NASCAR race at Talladega Superspeedway
used to force the cars to run with limited power
to keep speeds down.
The idea was to make the race safer,
but it also meant aerodynamic techniques
like the ones we've been talking about
were even more important.
In the final three laps of the 2012 race,
Keselowski and Bush formed a two-car tandem,
with Busch slipstreaming
and bump drafting the pair forward into the lead,
while also fighting aero-push through every turn.
The tandem technique for passing a pack
is a pretty common move.
But everybody knew that at Talladega,
the car in first place going into the final lap,
usually got passed by the trailing car
using a slingshot and a side-draft.
If you're the trailing car,
that move has to be timed just right
somewhere around the back straight,
or the car you pass can slipstream,
and slingshot you right back,
retaking the lead before the finish.
Keselowski knew that Busch
was waiting for just the right moment to make his move.
So on the final lap, going into the back straight,
Keselowski shook him off.
Keselowski moved right for just a moment,
and that move broke the tandem,
creating a low pressure drag that slowed Keselowski,
but also shoving a bunch of air in Busch's face,
breaking the tow.
The extra high pressure drag Busch had to contend with
from the unexpected movement
that Keselowski was able to pull off a small lead.
But for that lead to stick,
the timing had to be perfect.
Busch immediately ducked back into Keselowski's wake,
and with the extra speed from the slipstream,
started catching up.
Fortunately for Keselowski, with just one turn to go,
there wasn't enough race left
for Busch to attempt another slingshot.
Keselowski held onto the lead and won the race.
Afterwards, Keselowski said
he'd come up with the move months earlier,
even dreaming about it.
So if he was ever in that position,
in the last lap at Talladega,
he knew exactly what to do.
Because he shook Busch off with that little side move,
and made a charge for the finish,
commentators called it the shake and bake.
So, there you have it brutes,
the drafting techniques that make NASCAR strategy
complicated and fascinating at the same time.
But all of these moves can change next year
because there are new cars coming for 2022.
And we covered the NASCAR next gen project
in another episode, so go watch that
if you wanna learn more.
A lot of the new changes are aerodynamic,
and some of those are designed
to make the cars have less of an aerodynamic impact
on the other cars around them.
Maybe the side draft won't work as well as it did before.
Maybe the shake and bake will be dead forever.
It's pretty hard to say,
but we will see in a couple of years
when we go wheel to wheel racing in NASCAR.
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Thank you guys so much for watching this episode and B2B,
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Thank you guys so much for watching.
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Until next week,
bye for now.
(serene music)