- 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...
