- Every component of a car that was once mechanical
is becoming electronically-controlled.
Roll-up windows got replaced with electric ones.
Carburetors, that got replaced with fuel injection.
Heck, even your in-car flute is now just Apple CarPlay,
miss playing those flutie tunes.
(flute playing)
But there's one component that hasn't gone to zap town yet,
and maybe never will.
That's your brakes. But why is that?
Why have brakes not evolved from hydraulics to electronics?
What's stopping drive-by-wire brakes
from being added to cars, just like drive-by-wire throttle.
And why haven't the basics of brake technology changed
in over 100 years?
Well, I guess we'll never know unless I do a video about it.
Let's go.
(upbeat music)
- (groans) Big thanks to AutoZone for sponsoring this video.
We've all been there, right?
Driving around, minding your own business,
when, all of a sudden, bam!
Your check engine light comes.
- On. Hey James, yeah.
We're gonna be a little late.
Nolan's, check engine light came on.
- Worst of all, you realize you forgot
your OBD2 reader at home,
but don't worry because any nearby AutoZone
has got you covered. - Hey, hey, hey,
can I call you back?
Yeah, they're about to reveal the storefront,
which means we're cutting to an AutoZone.
- Got this, Jerry? - I got it.
- [Nolan] Your local AutoZone provides a Fix Finder service
for situations just like these.
- I bet you wish you brought your own reader, huh, Nolan
'cause this is gonna be pricey.
- Not only is it free,
but you'll work with an AutoZoner who uses the Fix Finder
to read OBD2 codes and uses an exclusive database
to find remedies, comparing verified fixes
across similar years, makes, models, engines, all for free.
Fix Finder will print and email you a list
of any applicable part solutions
or if your car needs a more serious repair,
AutoZone can use those readings to give you
a referral to professional shop.
The coolest part is Fix Finder will outline
your car's future problems
based on current service maintenance
interval recommendations.
- It says here in the report that your check engine light
is on because your gas cap may be loose.
I went ahead and sent that to your email as well.
- Thanks. - No problem.
- I was really worried there.
- [Jeremiah] Yeah. Yeah.
Well, you should be worried cause we're late.
So you know what that means.
- Jerry, we gotta get out of here.
Thank you! - No problem.
- An AutoZone is always nearby
with Fix Finder, the most complete free warning light report
backed by technician-verified fixes.
To learn more about the free Fix Finder service
and to find your nearest location,
click the link in the description below.
To understand what's happening,
let's first look at traditional hydraulic brakes.
When you press your brake pedal down in a normal car,
the lever of the pedal presses on a plunger
in the master cylinder.
This plunger is at the end of a sealed hydraulic system,
full of brake fluid.
As you press down the force exerted
by your foot becomes pressure in the fluid.
This pushes the brake fluid down the brake lines
to the next cylinder or in this case, the brake caliper.
There's one of these in each wheel
if you have four disc brakes and they push on pistons
inside the brake caliper or they move shoes
if you have drum brakes.
Those push your brake pads into the rotor, creating friction
and its friction that slows down the car.
Since this is a sealed hydraulic system,
there's almost no delay and every component moves
in tandem with your foot.
That's it.
It's simple, it's reliable, it's effective
and it's old as hell.
You know what's not simple, the YouTube algorithm.
And right now it really rewards likes.
So be sure to like this video and subscribe
if you're not already a subscriber.
Thank you so much.
So back to some science for a second,
how can your foot generate enough force
to stop an entire car?
Well, for that, we have to look at Pascal's Law.
Pascal Law states that any change
in the pressure on an enclosed fluid
is transmitted equally throughout the fluid
and is undiminished in all parts of the container.
Your pressure on one side has to equal the pressure
on the other, but for that to happen,
you either need a change in force or change in surface area.
So if we look at my very clean dirt bike,
we say we have a rear brake lever right here
that's connected to a master cylinder
with a line that runs all the way back to the rear caliper,
you spin that and it clamps down.
And the force clamping on the rear caliper
to be greater than the force applied by your foot,
the surface area inside the master cylinder
has to be smaller than the surface area and the caliper.
If you were to measure the piston surface area
in the caliper, it's going to be much bigger
than what's inside this master cylinder.
And you want that because now you get greater clamping force
on the rear end of the bike.
But we can also look at this equation in terms of work.
Work is the application of force over distance.
And it's that component of distance
that makes such a big difference.
And when you step on the brake pedal in your car,
your foot travels, a couple inches, right?
Five, six, seven, inches but at the brake pad,
the piston is only moving a fraction of the inch.
Same thing here, I push on this brake pedal right here,
right here, that's maybe a max of an inch of travel.
We go all the way back to the rear caliper,
you can see the pistons actually pushing on the brake pads
into the rotor and they're moving a fraction of an inch.
So to balance that equation,
those two need to be the same amount of work.
And since work is force times distance,
the force on the brake pads will be immensely greater
than the force applied by your foot.
This is the basic advantage of a hydraulic system
and it's used all the time to lift heavy things
and exert more force than your body can all at once.
Things like power-assisted braking and brake boosters,
they can make breaking more comfortable,
but they still revolve around this same process
of hydraulic transference.
But the main problem with hydraulic brakes
is that it will always require the system to be closed.
Any leak or cut in the brake lines
would be enough to stop that transfer of pressure
from making it to the wheels and your brakes
are not gonna work.
This is the kind of brake failure
that everyone thinks of in movies,
when someone cuts a brake line. (mumbling)
Crawling underneath the car and then (clicks tongue).
And now they drive away and then they're dead.
So there are problems with the old way of braking.
So how would electronic brakes fix those problems?
Well, first we need to see how they work.
I'm inside a 2022 Audi e-tron,
the first fully electric car
to include brake-by-wire technology.
Now when I push down on the brake pedal of this car,
there's a sensor that measures
the amount of brake pedal travel.
That information is sent over to an electric pump
that feeds hydraulic brake fluid into the calipers.
And it regulates the amount of clamping the brake pads do
on the rotors.
Now see, Audi is saying that this is a brake-by-wire system,
but actually it's much, much more than that.
See, I'm getting actual pressure feedback
from actual hydraulic fluid.
It's just not directly connected to the braking.
When I press on this pedal,
it still moves fluid inside the master cylinder.
That pressure simulates what feedback the brake
would be giving you and a pressure sensor
at the end of the master cylinder
is coupled to an electric pump
so that feedback can be exactly what it would be like
if the car had a purely hydraulic system.
The Audi e-tron is technically a dual-hydro-electric system.
It's a fully functioning hydraulic system
with a bypass put in it.
Ooh, and it works pretty good. Woop.
The electric system acts as a middleman
between the first half of the system,
that's the brakes and the master cylinder
and the second half, the calipers.
So this means while the two parts are mechanical,
the Audi can break with pedal input for emergency stops,
or it can see pedal pressure and use the electric motors
to slow you down instead of using the brake calipers.
This is how regenerative breaking works.
The inertia of the car is used to charge
the electric battery by driving
the electric motor in reverse.
But the point is,
even though this is an electronically-controlled system,
it still has good old hydraulics playing a major role.
In the unlikely event that you have an electronic failure,
your good old hydraulic system
is fully capable of bringing this car to a stop.
And that's great because one of the scariest things
on the planet is wanting to stop and then not being able to.
There are several reasons that manufacturers
would want to switch over to electric braking
instead of hydraulic.
The first would be to have computer-controlled braking
for automatic emergency braking systems.
The next would be to have variable braking,
soft breaking for the road,
but harsh braking for track mode.
And also as parts all go electronic,
there are fewer actual pieces to manufacture.
The easiest system would be a pedal
with a position sensor that tells a servo in each wheel
how much to clamp down on the brake rotors,
which would be pretty simple.
Now this all sounds great, Jerry.
You should sell products As Seen on TV.
I mean, you're very convincing salesman.
So what's the catch?
Well, there is a big as your mama problem
with electric brakes and that problem is us,
always freaking us, man.
We're always a problem.
We've driven for so long with hydraulic brakes
that the tactile feedback of a hydraulic system
is essential for normal driving.
The basic design of braking system hasn't changed
in 100 years.
Not since the Model A Duesenberg
have we really seen a new way to do brakes.
The problem with just have an electric system
with a pedal position sensor
is that there'd be no resistance in the pedal.
Audi had to add a pressor simulator
to the braking system just to make the pedal feel
like it was hydraulic.
It's hydraulic pressure but it's not direct feedback
from the actual brakes.
We've seen the same thing happen with steering.
As cars like the M3 changed
from hydraulic steering to electric steering,
many people complained that it didn't feel right
and BMW had to work hard to get that feeling back.
♪ You've lost that hydraulic feeling ♪
♪ Woo, woo, that hydraulic feeling ♪
♪ You've lost that hydro feeling ♪
♪ Now, it's gone ♪
♪ Again, gone, again, gone, again ♪
Now part of this is a legitimate concern.
There are many times when you know
what a car is doing by feel.
If you brake hard without ABS, you can feel it in your foot
when the brake is going to lock up and a skilled driver,
can feather that out and avoid locking up a wheel.
For most people though, they don't notice
the tactile feedback of the steering wheel
or the accelerator pedal,
but they definitely notice it in braking.
The major hurdle is not the brakes themselves,
but rather our brains.
See brakes are the main thing in your car
you never wanna fail, right?
If your accelerator stops working one day, that sucks,
but at least your brakes didn't fail you on a freeway
as you're approaching traffic.
We as humans, we trust brakes not to fail.
And we trust hydraulics to do that
because we aren't that familiar with hydraulic failure.
Now, electrical failures, we see those all the time.
Every time you update the OS on an old iPhone
or when your Xbox crashes,
'cause it's been stuck in that little IKEA cubby
with no way for it to vent heat
and you haven't cleaned the back of it
since the London Olympics, just dust everywhere,
it's just like sucking all the dust in and then it freezes.
You get it.
My point being, we see electronic failures all the time
because we're surrounded by electronics.
So even if electric brakes fail less often
than hydraulic brakes,
we'd still feel safer with the magic liquid pumps
that we've been using for the last century.
Hydraulic brakes, they're pretty well refined.
Don't get me wrong.
Only 2% of crashes in the US are caused by a brake failure.
And that's usually from people not changing their pads
and letting them wear out.
People, change your brake pads.
They're kind of important.
Now, unfortunately, I can't give you any other stats
on the failure rate of electric braking,
because right now there are no cars
that use a fully electric braking system.
And it's the same story with the C8 Corvette
and even the Tesla Model 3.
So not only do these cars have to run
an electric braking system,
they also have to run a full hydraulic system
just in case the first system fails.
I mean, come on, if humans just trusted electronics
and welcomed our new robot overlords,
we wouldn't have this problem.
(mumbling)
Now, currently, most...