05x11 - Big Rig Myths

[bunniefuu]

Narrator: on this trucking
episode of "mythbusters"...

[ Horn honking ]

...we've got three big stories
about big rigs.

Tory: that is crazy!

First up, there's
the dynamometer of death.

This is
the coolest toy ever!

Adam and jamie test
the gory story

That a truck tire blowout
can knock your block off.

Wow!

Then, buckle up as the team
takes on the knight rider.

I just hope the car still works
when I get my turn.

Adam and jamie ask, "can you
ramp it up on the highway?"

Adam:
holding it steady at 55.

And, finally,

Kari, tory, and grant
put their lives on the line...

It's getting dangerous now,
and that's how we like it.

...as they find out if drafting
increases your fuel efficiency.

Oh, my god!

Narrator:
who are the mythbusters?

Adam savage...

Is everybody ready
for diving?

...and jamie hyneman.

Gets me all worked up,
just looking at it.

That was beautiful!

Between them, more than 30 years
of special-effects experience.

That was heavy.

Joining them --
grant imahara...

Grant: jamie makes it look
so easy when he does it.

Narrator:
tory belleci...

Somebody order
some exploding pants?

...and kari byron...

High expl*sives and
electricity -- whoo!

They don't just tell
the myths.

They put them to the test.

--[Font color="#ffff00"] captions by vitac[/font] --
[font color="#00ffff"]www.vitac.com[/font]

Captions paid for by
discovery communications

We have a k*ller of a myth --
literally.

Bring it on.

Well,
you're in a vehicle

Alongside
a semitrailer truck,

And the myth is
that when the tire blows,

It's such
a powerful expl*si*n

That it will not only break
your windshield

But also
decapitate you.

[ Laughs ]

That is perfect
and right up our alley.

Tires can sure turn nasty.

Overpressurize them,
and the results are expl*sive.

But if you're unlucky enough
to be alongside

When a big-rig tire blows,

Would you literally lose
your head?

Dynamo-me -- dy-no-mo --
dyno -- dynamometer.

Dynamometer.

Now, I was thinking
this was a perfect thing

For spinning our truck tire
up to speed,

Except that nobody
west of the rockies

Is willing to let us blow
a truck tire

Anywhere near
their dynamometer.

We're gonna have to
make our own.

Why don't we do it
"mythbusters"-style?

We'll, say, get a really
powerful old pickup truck

And yank the bed off of it

And drive the pickup drive wheel
up to speed

Just underneath
the truck tire.

And that'll take the truck tire
up to speed, and we're there.

Let's do it.

In a typically ingenious
plan of action,

Adam and jamie will build their
own supersize dynamometer.

They'll sink a pickup truck,

Lower a big rig
onto the spinning wheels,

And put buster
in the firing line.

In 3...2...1.

And the first step
in taking buster's block off

With a blowout
is paring back this pickup.

Jamie:
we cut the sides off this truck

Because we need to expose
the drive wheel.

The drive wheel is gonna
provide the power

To turn
the big semitrailer tire,

So we need to get at that wheel.

We've got everything else
out of the way.

We'll put the semitrailer
on top of this

And fire this puppy up
and see what happens.

Narrator: jamie makes it
all sound so easy,

But at the chabot g*n range,

The reality is that
this is an enormous undertaking.

Our trailer's gonna
go here.

Our pickup truck's gonna
go [pop] there.

Narrator: the pickup's
drive wheels need to spin

At more than 50 miles an hour.

But so that
it can't go anywhere,

The mythbusters must sink
its tires into the ground.

Dude,
give it more gas!

Well, hell!

That ain't no truck no more.
That's a dynamometer!

With the dyno fired up,

Next, the boys need a big rig
to put on it,

And, uh, this should do.

Yeah!

Adam: I've just secured
our big-rig trailer

To the biggest forklift
we've ever used on the show,

Which is rated to 30,000 pounds,

As not only
a safety precaution,

But it's also a key part
of the experiment

In allowing us to adjust

How much pressure is actually
on the big rig's tire.

Narrator: with the forklift
locked and loaded,

The trailer is lowered
into position,

And once the two tires kiss,
everything's ready for a test.

Adam: [ laughs ]

Look at that!

Their dynamometer may be ugly,
but it works like a charm.

That's what you call
the ghetto dynamometer.

Narrator: so, now it's time
to burn rubber

And blow this big-rig myth
sky-high.

Jamie: it seems fine.
Adam: yeah, I agree.

We get it up to speed --
vroom.

Boom! Do it.

The big-rig myth
that we get to test

Happens to be one of the most
popular topics on the fan site.

Have you guys heard
of drafting?

Oh, that's when you try to get
up as close as possible

Behind a trailer of a big rig
to save fuel.

Yeah, the idea is

That the big rig
slices through the air,

Creates a low-pressure zone
in its wake,

And you need less fuel
to move your car.

Dude, I always wanted to try it,
but I just never had the nerve.

I was afraid that the driver
was gonna slam on the brakes.

Narrator: following a big rig
dangerously close

May seem like an insane way
to pass time,

But according to fans,
it can actually save you money.

The theory is that
the closer you tailgate a truck,

The more you'll decrease
the drag of air resistance,

And the more fuel you'll save.

Before we go full size
with this myth,

I think we ought to do
a few small-scale tests,

Just to see
if there's anything going on

Behind the big rig
aerodynamically.

If we're gonna test
aerodynamics,

I know nasa has
a wind tunnel.

I'd be happy to call them
and see if they'll work with us.

In the past,

The team have constructed their
own wind tunnels for testing.

That's exactly
what we're looking for.

But this time, they're going
straight to the big g*ns --

Nasa.

And the idea is that
the wind flowing through here

Is very even and steady.

We're gonna blow smoke through,
over our model big rig,

And if we see that smoke
collecting at the back end,

That indicates
a low-pressure zone.

Narrator:
with the high-speed camera
primed to catch the action,

It's all systems go
for the smoke and wind.

To the naked eye,
it's hard to see a pattern,

But things become crystal clear
on the high-speed.

There's an obvious dead zone,

A protected area where the
oncoming smoke doesn't reach,

Protecting any following car
from drag.

Tory: smoke was gathering
behind the truck,

Which proves to us that there
is a low-pressure area.

What we're gonna do now
is take a car

In the same scale as the truck,
attach it to a force gauge,

And then see what kind of effect

That low pressure has
on the car.

Narrator:
but just before that,
the team first needs a baseline,

So the truck is removed
from the track

To see what the force
of the oncoming wind is like

On the car alone.

With the smoke off, it may look
like nothing's happening,

But the wind is roaring
past the car

At over 50 miles per hour.

And grant gets a reading.

Okay, so, it looks like we got
a good baseline.

Definitely.

.142 pounds,

And that is just
the wind on the car alone.

So, that's the control.

The question now is,
will this figure reduce

With a semi shielding
the airstream?

Kari: we're now a full
seven car lengths away.

Do we have any drag
whatsoever?

We have


Are you serious?
Yeah.

Wow!

For kari,
that was the "wow" factor.

So, how about when the car
gets dangerously close?

First, they wind the truck in

To decrease the distance
to 5 inches,

Or 10 feet
if this were full scale.

Tory: all right,
so, we're at 10 feet.

That's a 60% reduction
in drag.

Kari: whoa!

That is insanity!

All right, we're at 6 feet away
from the truck.

That is ridiculous.

I don't think
I'd want to drive that close

To the back of a truck.
No way.

Let me tell you,
you might want to reconsider --



Oh, my god!

Let's go
to the suicide zone.

All right.
Let's go to two feet.

What are we reading?

You know what's crazy?

We're reading 93% reduction
in drag.

Are you serious?
Yeah.

Narrator:
it's an astounding result,

But would this actually
translate to fuel savings

On the open road?

Well, there's only one way
to find out.

The team will have to go
full scale

And test this myth for real.

This is great evidence for us
to go on to the full-scale test.

Absolutely. We need a big rig.
We need a car.

And we definitely need
to investigate this further.

And we need
a crazy driver.

Who's that gonna be?

Welcome back.

The myth we're testing is

If you're driving alongside
a big rig when its tire blows,

Can that exploding tire
k*ll you,

Or, specifically, behead you?

So, this is our big rig,

Suspended in midair
by our 30,000-pound forklift.

We are going to lower this down
onto our dynamometer.

I know it looks like
a pickup truck,

But, in fact,
it's a dynamometer.

It'll spin up to speed,

Spinning this wheel
in the correct direction.

We are going to make this tire
fail by hell or high water,

And that failing tire,
hopefully,

Will knock buster's head
right off his body.

Jamie: the reason we're using
a motorcycle here

Is because this is
a worst-case scenario.

Obviously, on a motorcycle,
you're a lot more exposed.

And so, if a big tire
like this goes off,

While we could have put
a car there,

We figure this is
the nastiest thing we can do

With this particular experiment.

Narrator: things are only
going to get nastier for buster,

Because to blow the tire,

Adam and jamie are going
with the, uh, direct approach.

That's the shotgun.

And what we're hoping --
if everything goes really well,

What will happen is
that slug will enter the tire

Right about here
and compromise the radial.

That's the steel wires

That run around the perimeter
of the tire.

Once that radial
gets compromised,

If the gods are shining on us,

This thing will open up
like a zipper

And fail
in a magnificent fashion,

Slicing buster's head right off.

Narrator:
with the dynamometer spinning,

It's time for the magic b*llet.

Of course, this isn't a typical
way for a truck tire to blow,

But this should result

In the catastrophic failure
that this myth needs.

Adam: okay.

This is tire-blowout
shotgun shell.

Revving the engine.

[ Hissing ]

That's a hit, man!
Nicely done.

I heard it do a
[hisses]

Yep.

But that was not the
catastrophic failure we wanted.

Narrator: jamie was
right on the money,

Hitting the tire dead-on,
but there sure was no expl*si*n.

That's a neat hole.
It's right there.

That's the hole?!

Well, that ought to
tell us something.

I mean, that b*llet's
that big around, you know.

They don't get any bigger
than that,

And it hit it clean,
right in the sidewall.

It had to hit
some of those cables.

That was full pressure,
and it was a perfect hit, so...

The high-speed shows
the moment of impact

As the slug pierces the tire,

But buster's white-knuckle ride
is unaffected.

To get a tire expl*si*n,
you're going to need a plan "b."

Adam: we have to come up with
a new plan

Because what we're doing
isn't working.

These tires are super crazy
incredibly resilient.

Narrator: supposing you're silly
enough to tailgate a truck --

Would this dangerous stunt
really improve your gas mileage?

Tory, grant,
and kari's wind-tunnel tests

Have given this myth
the thumbs-up...in theory.

That is so much more
than I expected.

Narrator:
but what about in practice?

Time to go full scale.

We should drive at different
distances behind the truck.

We'll start at 100 feet
and move our way up to 2 feet

And see if we save fuel
as we get closer to the truck.


Who's gonna drive?

I think grant should do it,

'Cause he had his middle name
legally changed to "danger."

Grant "danger" imahara --

I like the sound of that.

Narrator: the mythbusters
also like the look

Of the impressive beast
they've lined up

For their full-scale test...

At the portland, oregon,
headquarters

Of one of america's leading
rig makers, freightliner.

Markstaller: we've got this new
cascadia freightliner here.

It took 2,500 hours to shape
the aerodynamics of this truck

To make it the most
fuel-efficient truck

In the world.

It's a brand-new truck,

And we're anxious to get it
out on the track again

And help you with that myth.

Narrator: test engineer
matt markstaller

Reckons drafting is suicidal,

Especially considering how many
blind spots are on a big rig.

But he's agreed to help out
under controlled conditions...

[ Engine turns over ]

...which include
a thorough workout for grant

Under the tutelage of hollywood
stunt driver mike ryan.

We actually want to build
all the way up

To a 2-foot distance
between us and the truck.

How dangerous
is something like that?

Definitely,
definitely something

You don't want
to encourage people to do.

I mean,
I think the statistic is

About 3/4 of all the truck
accidents in the world

That involve a car
and a semi truck

That have a fatality

Were caused by the person
driving the car.

It's pretty scary.

Tory: I'm gonna put a line
across the track.

That's gonna be
their starting point.

They're gonna drive down
a quarter of a mile,

Put another mark.

Then, we're gonna have
a half a mile

To see how much fuel
is being used.

Narrator: it's on this
half mile of track

That the team will measure
grant's fuel consumption,

And that's test engineer
andrew smith's department.

What we've got here is
our data-acquisition system,

And we're hooked up
to the fuel-injection system.

In fact, what we're doing
is exactly the same

As if we were physically
measuring the fuel

That's going to the engine.

We're recording all of that,
and we can compare

When we're behind the big rig
and when we're not.

Narrator: once the fuel gauge
is in place,

Grant will make several runs
behind the rig

At 55 miles an hour,

Working his way incrementally
from 100 feet

Down to 2 feet.

But, first up,
it's the baseline.

This will be our control test.

I'm gonna drive along.

We're gonna measure data
for half a mile,

And I'll see
how much fuel I'm using

With nothing in front of me.

Narrator:
with andrew riding shotgun,

Grant puts the pedal
to the metal.

Okay, approaching drag strip,

Holding at 55.

Still holding at 55.

Approaching the stop.

That's it.

Narrator:
andrew crunches the numbers,

And it turns out that driving

At 55 miles per hour
on the test track

Gave a fuel consumption
of 32 miles per gallon.

Will drafting really cause
an increase in mpg?

We're gonna do it at 100 feet,




Which I consider
somewhat suicidal

If you were driving
on the highway.



♪ All right ♪

Narrator:
grant starts out at a distance

Of 100 feet behind the truck,

But even this is considered
outside the safety zone

For most road authorities,
who recommend at least 150 feet

Between vehicles traveling
at 55 miles per hour.

Crossing
the finish line now.

Grant: okay, so, that was
a good run at 100 feet.

Maintained a constant distance
at 55 miles per hour.

Narrator: and the result
is pretty dramatic.

With 100 feet between car
and rig,

Fuel consumption improved
by over 10%.

Next, grant gets back up
to 55 miles an hour

And closes the gap to 50 feet.

Kari:
we're gonna hold this speed.

You can collect
your data now.

With this size gap,

Fuel consumption improved
by 20% on the control.

Grant moves in even closer,
to 20 feet.

This is starting to get hairy.

He's starting to approach
that blind spot.

I can't see him.
Can you?

At 20 feet, the slipstreaming
effect of tailing the truck

Has improved fuel efficiency
by an amazing 27%.

But what about tailgating
a big rig at 10 feet?

Tory:
it's getting dangerous now,

And that's how we like it.

Narrator:
in the wrong hands,

Tires can be
downright dangerous.

But can they k*ll
if they explode?

Well, for adam and jamie,

Getting a tire to explode
in the first place

Is proving somewhat troublesome.

That was not the catastrophic
failure we wanted.

So, to try
to turn a tire torpedo,

The team is next going to
replicate the last moments

Of a tire that's done way
too many miles,

And subjecting another tire
to high heat

And low pressure
should do just that.

Yeah, we need to heat it up
with the external heaters,

And we need to really
reduce the p.s.i.

So that we can get
the tire flexing,

'Cause that adds heat,
as well.

Narrator:
flexing is responsible

For most blowouts
on highway trucks.

If air pressure is too low,
the rubber wobbles, or flexes,

And this flexing can cause
rapid expl*sive disintegration.

Jamie: we've got heaters posed
on both sides of the tire,

And the idea is to bring
the overall tire temperature

Up as high as we can get it
with them.

We're gonna start off slow,

Kind of like
a chicken on a spit,

And we're gonna try
and roast the tire.

And we'll be looking at this
on the thermal-imaging camera.

Then, hopefully,
somewhere in there,

With all that flexing
and all that heat,

We'll get
a catastrophic failure.

Narrator: once the new tire
is inflated to 30 p.s.i.,

A quarter of its usual pressure,

The dynamometer is, um,
ready to roll.

Adam: well, we're rotating
the tire under stress.

It's been going
for about five minutes,

And it's already at 150 degrees.

That's the external,
outer temperature of the tire.

We know that the tires start
to attain their failure mode

Around 350 degrees.

So that's where our butter zone
is gonna be in this, hopefully.

We just got to see
how long it takes to get there.

Narrator: but, unfortunately,
even after 10 minutes,

The butter zone has not
been reached.

It's capped there.
It's just sticking around 200.

Narrator:
although heat failed to fire up
the low-pressure tire,

All is not lost,

Because the mythbusters have
another trick up their sleeves.

Will suddenly
over-pressurizing the tire

Result in the biker beheading
they're after?

Adam:
in this line, it's 150 p.s.i.

When I hook it up, this is gonna
pass that onto the tire,

And if the tire's sufficiently
weakened, it's gonna blow.

Exploding tire --
hopefully, final test --

In 3...2...1.

[ Air hisses ]

Come on, baby!

Come on.

There we go.

That was it.
That was it?!

[ Laughs ]

It looks just like
a zipper.

It -- you know, it opened up
where you cut it.

But it didn't propagate.

No.
No.

It didn't really --
that wasn't very satisfying.

It wasn't what we're looking
for here.

Narrator:
this time, the tire did fail,

But it still didn't fail
catastrophically.

With this myth deflating fast,
adam has one final plan.

You know,
well, we've seen the blowout.

Let's put it under a little
pressure on the bottom tire

And spin it up to speed,

See if we can get some shrapnel
out of it.

More!

Adam reckons that if the burst
tire spins long enough,

Something's got to give.

And sure enough,
as the dyno picks up speed,

Rubber shrapnel soon starts
flying far and wide.

Whoa!

But have any
of these tire torpedoes

Toppled our wild hog buster?

This is
the coolest toy ever!

I think
we better pull over!

Although rubber shrapnel
did get flung,

None of it hit our biker.

So, what does this mean
for the myth?

If we look at the footage
from that camera over there,

You'll see one of
the large chunks of rubber

That flew about 200 feet
in that direction.

I watched one piece go maybe 70,


We need to actually
find out what happens

When you do get hit.

Yeah, we need to make it
a nonrandom event.

We need to make
a rubber chucker.

We need to make something
that chucks chunks --

Large chunks of rubber --
right at buster's head

To see what kind of damage
it will do.

Narrator:
but before all that,

It's time to get k.i.t.t.ed out
with another myth.

Okay,
so, what have we got now?

Well, I've got a big-rig myth
of my own.

Have you ever seen the show
from the early '80s

Called "knight rider"?

Yeah, wasn't the car
intelligent or something?

It was. Do you remember how
that car came in for repairs?

Yeah, he drove it right up
into the back of a big rig.

At speed.
Yeah.

I want to know
if that's really possible,

Or if when your 60-mile-an-hour
drive wheel hits that ramp --

Boom -- launches you
right into the container.

Well,
wear your seat belt.

[ Laughs ]
I will.

Narrator: before the hoff
was the hoff,

He was the knight rider.

And his ride?

Well, this four-wheeled
black beauty

Was smarter
than your average car.

And if it needed
running repairs,

There was the famous
high-speed entry

Into the team's mobile h.q.

But in real life,
once you hit the ramp,

Wouldn't you suddenly accelerate

And catapult yourself
through the cabin?

You know, obviously,
we're gonna go full scale,

But I think we ought to go
small scale first.

Let's get, like, an r.c. Car
and a running treadmill

And just do the whole experiment
in miniature first.

Okay.

Narrator: yep, it's the patented
mythbuster bench test.

In this setup, adam builds the
scaled-down remote-control car.

Yeah.
Look at that.

Narrator:
and jamie vandalizes a treadmill

To replicate the rolling surface
of the highway.

Ingenious!

Jamie: the treadmill here
represents the road surface.

We have a miniature
representation of a truck.

We have a miniature car,

So, the main thing
that we're looking for here

Is what happens when the car
makes the transition fully

From the road surface,
onto the truck --

If it were to do something
like a wheelie

Or just spin out of control,

Not get traction,
or something weird like that.

Narrator: as jamie said,

The crucial moment
is when the tires of the car

Get traction on the ramp.

At that point,

Both vehicles are traveling
at much the same velocity.

But once it hits the ramp,
the car is now moving at speed,

And in comparison,
the truck is stationary.

And the theory is, without
a special-effects department,

Wouldn't that cause it
to accelerate out of control?

But that's just the theory.

How about the practice?

Ready?
Yeah.

There you go.

Narrator:
no need for practice.

In a break
with "mythbuster" tradition,

There was first-time success
with a small-scale test.

We've been thinking that
the moment those back wheels,

Traveling at this speed,
hit this ramp,

That car goes fa-ching.

Narrator:
the high-speed camera confirms
there's no fa-ching factor.

The r.c. Car slid into the
trailer as smooth as you like.

And even without brakes,
its entry was slow enough

To prevent
a serious fender bender

With the back wall
of the big rig.

So, I don't know about you,
but the small-scale experiment

Really gave me
a lot of confidence

That this might actually
be possible.

Yeah, and when
you think about it,

The car has got
a lot of inertia,

And for this to crash
into the back of the semi,

It'd have to all of a sudden be
going twice as fast as it was.

It's got to really
accelerate.

Well, I mean, the only thing
for us to do now

Is to go full scale.
Yep.

Let's get to building a ramp.
Okay.

Narrator:
when driving behind a big rig,

If you're too close
to see the truck's mirrors,

Then the truck driver
can't see you.

That's why drafting
is so dangerous,

Not to mention ill*gal.

But, as kari, tory,
and grant have found out,

This suicidal driving technique

Does increase
your miles per gallon.

At a drafting distance
of 20 feet,

The team has seen
their fuel efficiency

Increase dramatically.

But grant "danger" imahara

Laughs in the face
of his middle name.

With mike riding shotgun...

Okay, I'm buckling up.

[ Laughs ]

...he's going to tailgate
a truck at 10 feet.

I think if you were gonna try
to draft a big rig

At 10 feet behind them,

You are completely mental.

Even in a controlled situation,
it's really, really scary.

[ Horn honking ]

We're ready!

All right, let's go.
In 3...2...1...go.

Go.



Ryan: still have one more shift,
and then you can do it.

Okay, we've hit 55.
We're holding steady.

He's completely in
our blind spot,

And we can't see him
at all.

Narrator: the recommended driver
reaction time for this speed

Is 2 seconds,

Meaning 150 feet
between vehicles.

Ryan:
we're still with you.

At 10 feet,

Grant's reaction time is down
to almost 1/10 of a second.

Sweet driving, grant.

Okay --
returning to the start.

Narrator: it may be madness,
but the stats don't lie.

With a distance of 10 feet
between car and truck,

Fuel efficiency improves
by almost 40%.

But this myth ain't over yet,

As grant prepares to draft at
the insane distance of two feet.

At two feet, one miscalculation,

And our mythbuster will be
six feet under.

This is it.

The car is 2 feet
behind the truck,

And they're gonna be traveling
at 55 miles an hour.

I mean, this is nuts.

I'm a little freaked out
right now.

I mean,
we did a lot of training,

But that was with a minivan.

This is a big rig.

All right, you ready?
Let's do it.

I'll see you
on the other side.

It was nice knowing you.

Narrator:
what's not nice knowing is,

If the rig
has to stop suddenly,

Grant will have .03 seconds
to react --

Faster than the blink of an eye.



Kari:
okay, here we go.

Can't even see grant.

Just hit 55.
What's your 20, little buddy?

Ryan:
we're 3 feet out and closing,

Just bringing it on in.

We are locked in
to the 2 foot.

Oh, you are totally
in our blind spot,

Completely riding us.

Narrator: matt,
at the wheel of the big rig,

Can't see grant's vehicle
at all.

That is crazy!

Yeah, boy!

Oh, he just crossed it.

[ Laughs ]

Whoo!

[ Laughing ]

Oh, my god!

That was crazy.

[ Laughter ]

How much gas
am I gonna save?

Narrator: well,
the result comes with a twist.

Up until now, every time
grant's vehicle moved closer,

Fuel efficiency increased.

But at two feet, it went down.

The fuel economy actually
dropped off a little bit,

And I think the reason was

There was such little air drag
at that point,

It was so hard to keep
that 2-feet distance --

That you were always kind of
feathering the throttle --

On the throttle, backing off,

And so that actually hurt
the fuel economy.

You want a really steady foot.

Narrator: so, apart from nervous
footwork on the accelerator

When grant drove like a maniac,

It looks like drafting,
as dangerous as it is,

Does improve fuel efficiency,
after all.

But, really, it's just not worth
risking your life for.

Dude, nice job!

You got nerves of steel.

Thanks.

You know,
it was really intense,

But we got a great result.

Surprisingly, at 2 feet
behind the truck,

It was less
fuel-efficient,

Because it's so difficult trying
to keep that distance

Between you
and the truck.

Yeah, difficult and crazy.

But did you know

That even driving at 100 feet
is dangerous?

Our researchers found
that at 55 miles an hour,

The minimum safe stopping
distance you should allow

Is 150 feet.

So, what are we gonna call
this one?

I think we have to call
this one confirmed.

You do save fuel drafting
behind a big rig.

But it's absolutely not
worth your life.

Narrator: incredibly,
adam and jamie have had reason

To doubt the hoff.

They're questioning
the signature stunt

From his "knight rider" days.

Can you really drive up the ramp
of a moving big rig,

Or is it a mythical maneuver?

To find out, they followed kari,
grant, and tory

To the madras test track
in oregon.

So, we've already done this test
in small scale in the shop.

And the small-scale test
really made it clear

That this might
actually be feasible,

That the car's inertia
would keep it from doing

What we thought it might do
in the worst-case scenario,

Which is to sh**t up that ramp

And right into the big rig
in a terrible wreck.

So we've come here
to try it out full scale

And see if we can do it safely.

Narrator:
it's a simple recipe.

Take one big rig,
one 1980s sports car,

And ramp them up
at highway speeds --

And not just any ramp.

Adam and jamie have custom-built
their own.

After all,
it's their lives at stake.

Jamie:
and not an inch to spare.

The ramp seems like
it's perfect.

It seems to be just long enough
to do the job

And not really hit much
on the car.

[ Clunk ]

It does a little bit,

But it seems like it clears
everything just barely.

So I think we're good to go.

Narrator:
now, the team has been

Behind the wheel
for the show before.

But they were drunk...

[ Belches ]

...on the phone...

Hi!

...and driving around
in circles.

[ Yawns ]

Uh-oh.

Not exactly ideal preparation

For a tricky
high-speed maneuver.

So it's stunt driving 101.

That's a nice maneuver.

All right, guys.

You ready for some
driving lessons

So we can try out
this myth?

It's a hollywood entrance,

But mike soon gets down
to business.

I want to show you
some spin control,

Some slide control.

I want you to get out there

And spin the car around
a little bit

So you have an understanding
what the car might do

If it did come off
the ramp.

You're trying to hit
a very narrow 8-foot-wide ramp

In a car that's over 6 feet wide
at highway speeds.

So you're gonna have
to be very precise.

If something did go wrong,

At least you'd know
what that felt like already.

Mike thinks hitting the ramp

And applying the brakes
at the top is the easy part.

He wants to prepare
adam and jamie

In case something goes wrong.

[ Tires screech ]

And with just inches to spare
on either side of the ramp,

That's a definite possibility.

Yank it.

[ Tires screech ]

[ Laughs ]

There you go.
Nice. Nice.

But spinning dangerously
out of control

Is the reason adam gets up
in the morning.

I just hope the car still works
when I get my turn.

Reluctantly our budding nascar
driver gives it up for jamie.

But the bereted one buckles up
and takes off

Like he's auditioning
for "driving miss daisy."

No foot brake.

Oh, yeah.

It's hard.
Yeah.

It's taking a little longer.

He's an old man.
What are you gonna do?

But as the mythbusters know,

You can teach an old dog
new tricks.

And jamie soon has the hang

Of getting an out-of-control car
under control.

Okay, turn.

[ Tires screech ]

With jamie's lesson finished,
school's out.

But did they pass?

Adam: you think we're ready --
ready to try this thing?

I think you guys
did a great job.

Narrator:
mike's seal of approval

Means they can move on
to the real thing.

And with both vehicles
on the starting grid,

The team meet the bigwig
with the big rig.

I can't wait
to do this!

Hey, matt.

How are you?

Good. How are you?
Very good.

So you're gonna be
our driver, huh?

That's right.

So, what's the top speed
on this puppy?

Well, we can go as fast

As you guys are comfortable
getting into the back.

[ Adam laughs ]

Narrator:
it's tempting,

But in an unexpected moment
of caution,

Adam advocates
a safety-first approach.

Adam: we're hoping to get up
to highway speeds,

But we're gonna start slow.



Is what the first test
is gonna be at.

And if that works,
then we go to 55.

Narrator:
the question now is,

Who will be first
in the driver's seat?

Jamie:
if adam doesn't die
during this experiment,

Or maybe if he does,

Then, you know,
I'll have to have a go.

But, at any rate, adam will be
the first guinea pig.

And if it seems okay,
I'll go in.

Narrator: so adam,
the human guinea pig,

Suits up
for the 35-mile-an-hour run.

And with just one
successful bench test

And a 1980s tv show to go on,

They're taking no chances
with safety.

Adam: there's still a lot
that can go wrong,

Which is why we've done
a bunch of safety procedures

To make this
as safe as possible.

One, we've added a roll cage
into this car.

Two, we've added
a five-point safety harness

So that if I roll,
I'm not going anywhere.

And finally,
I'm wearing a helmet.

Narrator:
this is it -- test time.

Gentlemen,
start your engines.

Narrator:
but just as they get underway,

It starts raining,
making the road and ramp slick

And the challenge
just that little bit tougher.

While adam is driving up
into the back of this truck,

Hopefully,

I'm going to be driving
right alongside with mike,

Who will be coaching adam

In case he sees something
going wrong.

Narrator: adam accelerates,
approaching his target speed.

Adam: we're at 25,
going to 30.

We're at 35 miles an hour.

He takes his time,

Getting precisely in line
with the ramp,

And when he's close enough,
mike gives him the cue.

Okay.
Let's go for it.

Look at that!

Well done.
Well done.

The high-speed camera captures
the crucial moment.

As the wheels hit the ramp,
they slow down significantly,

Which is where
the clever science bit comes in.

Any object in motion
has a tendency

To maintain a constant velocity.

This law of inertia acts against
the acceleration of the car

As it hits the stationary ramp,

Slowing the car to a crawl

And giving adam
plenty of time to stop.

That worked beautifully!

That was a cinch!
That was so easy!

Narrator: which means
there's only one thing for it.

They're going the whole hoff.

I feel like
I'm ready to go to 60.

Let's make it 55.

That's the legal speed limit,
I think, on these things.

Perfect.
Let's do it.

All right.

Making it safely up
that 6-foot gap

At 55 miles per hour is
a tougher proposition than 35,

And the rain
is coming down harder.

Let's do it.

Adam g*ns the engine and
hits the speed ceiling quickly.

We're at 55 right now.

Holding steady at 55.

Jamie and mike are once again
in support,

Unless he crashes.

Then he's on his own.

Ryan:
adam, bring it on.

Be careful, brother.
It's slick.

Look at that!

Good job.

[ Laughs ]

Whoo!

Once again,
adam made it look easy.

The increased velocity
didn't change a thing.

The wheels hit the ramp.

The car's inertia prevents
any crazy acceleration,

And adam parks it.

Nice, man.
Great job.

Great! Awesome!

Dude, that was scary!

Yeah, that was pretty --

I was a little nervous there
watching you do that.

Narrator:
with the myth confirmed,

There's only one thing
left to do.

It's jamie's turn.

Jamie: this is jamie.
I'm good to go. Over.

And he's going to prove
that whatever adam can do...

Adam: holding.

...he can do backwards.

[ Laughs ]

Nice work, hyneman!

[ Tires screech ]

Move over, the hoff.

The hyneman is here.

So, the truck-ramp
"knight rider" sequence

All worked like
a charm.

I mean, we were able to do
everything we tried to do.

Absolutely.

One of the things I love most
about doing this show

Is the weird skills we get
to learn, like stunt driving.

I don't know when I'm gonna have
a chance to use it next,

But it's nice
to know how to do.

Exactly, and the "knight rider"
ramp drive-up --

Totally confirmed.

It worked.
Confirmed.

Narrator:
there's no doubt about it.

Tires can provide hours
of entertainment,

But can these innocent
rubber doughnuts

Become lethal k*lling machines?

Well, not if the mythbusters
are anything to go by.

Their dynamometer tests
sure burned some rubber...

Whoa!

...but buster came out
unscathed.

I have to admit,
I'm disappointed.

I really wanted to see our rig
make a truck tire fail

Under pressure
at highway speeds.

Well, you know, I felt
the same way at first, too,

But after thinking
about it,

The tire disintegrated
exactly the way it would

On the highway
at those speeds.

The only thing
we really did not get

While we were out there
was seeing an impact

From some of those frags
into a dummy.

Suppose that's what
we do now.

We take our biggest chunk
of rubber,

We calculate the speed
it left our rig at,

And here in the shop,

We fire it at that speed
into a head

And see what kind of damage
it would do.

Okay, I think we can modify
the same rig that we had

To do specifically that --
to aim it right at a head --

And then we'll know
whether it works or not.

I think it's a terrific way
to finish this up.

All right.
Let's do it.

Terrific, indeed.

The plan is to hoist up
the pickup truck

And sit the drive wheel on
another freely spinning wheel.

Then, a piece of big-rig tire

Will be placed
between the wheels,

And when the pickup revs up,

The tire will be shot out
the other side towards buster.

So, fresh from the mud,

The pickup is driven into place.

Looks good, looks good.

Looks good.

I'm here for you, buddy.
Okay.

An upturned trailer will provide
the lower spin wheel

For their rubber chucker.

Adam and jamie
slide it into place

Beneath the pickup truck.

I swear,
this is the perfect height.

Now, one thing
we need to remember

Is the proclivity
of your forklift to drift,

So we'll want to put
one of those farm stands

Underneath it
or something.

So jamie welds some crossbars
for stability,

And their rough-and-ready
rubber chucker

Is up and running.

This whole thing is another
lesson in not messing around.

I mean, we have a trailer.
We have a truck.

We got the power.
We have wheels.

Let's just kind of, like,
put one here, put one there,

And we'll sh**t
some tire rubber.

Narrator:
adam is going to be the driver

In charge of the speed
at which the wheels spin.

Adam: 20, 25, 30.

And when he hits 40, jamie
will feed a strip of rubber

That came off
their earlier big-rig blowout

Between the wheels.



Oh!

[ Laughter ]

A hole in one
on their test board.

Adam can barely
contain himself.

Wow.

There's nothing left
but to get this test set up

With the head...

And just go.

That is awesome.

This one was going


Which is, by the best math that
we could do on its trajectory

And the height it went
in the air,

About how fast that piece
of rubber was going

When it left our truck
out at the range.

So if this beheads the guy,

I'd say this myth is confirmed.

Narrator: the human analog
for the beheading guy

Has been molded from ballistics
gel with a pig-spine neck bone.

Adam:
look at that.

That's grant with a spine.

How you doing, buddy?

Narrator:
adam and jamie place him

Directly in the path
of the tire belt.

Jamie: we've seen
that there's a lot of energy

Contained in these tires
when they're spinning,

And if they disintegrate,

They can throw pieces
of themselves at high velocity.

So this test is going to see
whether these tires

Can penetrate a car window,

Whether they can actually
break someone's neck.

That's effectively
what the myth is about.

Narrator: with the potential
power of this rig,

Adam and jamie are taking things
to the extreme.

Gone is biker buster,

And instead, they'll be firing
a tire belt at 40 miles per hour

Through a car window
at the driver's head.

Okay, well,
let's fire the truck up

And see what this puppy
will do.

Right.

[ Engine turns over ]

Adam: 25...





Go!

Wow!

That was awesome, dude!

Narrator: amazingly,
an almost total head-lob,

First time at the plate.

His neck was broken.

Oh, he's k*lled.
He's completely dead.

Well, it pulled his spine
out of of his head.

Anyone coming upon
this scene of an accident

Would say,
"the body was beheaded."

Narrator:
and any chances for recovery

Are going...going...

Gone.

Viewed on high speed,

The force of the impact
is frightening,

And it's clear
that the only driving

Our ballistics-gel dummy
would be doing

Is in a hearse.

Oh, it's a perfect hit.

That's -- oh, my god.

I mean, it's just like --
there's nothing there.

Final wrap-up --

What's the verdict
on exploding truck tires?

There's not really
any two ways about it.

If this thing hits you
at 40 miles an hour

Or some other
highway speed,

It could
cut your head off.

It's confirmed.

I totally agree --
confirmed.