BRAKES: How They Work | Science Garage

BRAKES: How They Work | Science Garage

– We’ve all been there.
You’re driving along
when something happened.
Today, we’re gonna look at the main thing
that saves your butt in
situations like that,
your brakes.
Alright, everybody bring it in.
– [All] And
– The core concept of a vehicle’s
braking system is simple.
An object is in motion
and it needs to stop being in motion.
Brakes use friction to decelerate.
The wheel has energy in
the form of movement.
The brakes apply friction
and create heat energy.
Once all the movement energy
is transformed into heat,
your car stops.
It’s not magic, it’s physics.
To stop, you need friction.
This simple concept
is what almost all vehicle share
in their efforts to come to a stop.
What isn’t shared between vehicles
is how that friction is applied
after the pedal is pressed.
The very first brakes
were just pieces of wood
that pushed on the wheels.
It worked, but it wasn’t that great
because it beat the crap out of the wheel.
(speaks in Russian)
The simple solution
was to attach something to the wheel
and slow that down.
In 1900, Wilhelm Maybach
became the first car maker
to put a drum on a wheel
to assist with braking.
Slowing down the drum meant the
wheel woudn’t take the wear.
Good thinking, guys.
Here’s what a drum brake looks like.
This drum is attached to the wheel.
Inside of it are these
two heat-resistant pads.
When you press the brake pedal,
these pads are squeezes
up against the drum.
The pad slow the drum
and the drum stops the wheel.
Early cars also used a
bunch of cables and pulleys
to get the pressure from
the pedal to the wheel.
When you push the pedal,
it pulled the cable,
and the brake wires needed
a lot of maintenance,
and often they snap when
you needed them the most.
Another downside was
the precision required.
If a lever was off or a
wire was tensioned wrong,
the different wheels
would receive different braking pressures,
and that’s just unsafe.
Hydraulic brakes on the other hand
use pressurized fluid to push the brakes.
When you hit the pedal,
a plunger depresses in
the master cylinder.
That sends the pressure
through all of the brake lines
to all four wheels at once.
Hydraulic brake lines rarely rupture.
They don’t require the
maintenance of mechanical lines
and they required very little
pressure from the pedal
to be effective.
By 1950, hydraulic brakes
were really the only braking
systems left in cars.
Drum brakes were pretty good,
and we use them in most
of the production cars
up into the ’80s.
Their major drawback, however,
was that under intense
conditions with frequent braking,
they got really hot.
If they’re too hot, they can’t change
the energy of motion into heat.
That’s bad,
because that’s when
you need them the most.
Let’s build some better brakes.
An increased coefficient
means better braking,
but it also means you need better cooling.
One way to create more friction
is with the materials in the pad.
Pads have to be strong
enough to stop a wheel,
but strong enough not to damage the drum
or sound like death.
Another way to increase friction
is to apply more pressure.
Drum brakes push out.
The brain trust making brakes realized
you can create more
pressure by squeezing in.
And lastly, you have to
increase suffice area
the greater surface
area means more friction
The best way to improve
friction and avoid heat
is lose the drum, squeeze to a stop,
and increase surface area.
So instead of a drum, they use a disk.
The disk or rotor is attached to the wheel
and rides inside a caliper.
The caliper squeezes the
brake pads against the rotor
and the wheel comes to a stop.
Disk brakes cool off better
because they’re not inside of a drum.
The air cools them.
The bigger the brake and
caliper combination is,
the more friction they can generate
and the more easily they
can dissipate the heat.
Like many automotive advancements,
the first disk brakes used in racing
were in Formula 1 in 1951.
In 1955, Citroen became the first company
to put them on production cars.
They were more expensive to manufacture,
but as cars became faster,
disk brakes became necessary.
That’s not to say that drum
brakes are more dangerous.
We still use drum brakes.
When a vehicle slows,
it’s weight gets transferred
mostly to the front axle.
The front brake usually
does about 70% of the work,
leaving the back brakes
with a lighter load.
James, what are you doing, man?
– What are you doing driving
in the freaking street?
– Sorry almost hit you.
We cool?
– Because drum brakes are cheaper
and simpler to produce and maintain,
most auto makers use them on lighter cars
or entry level models because,
well, because they’re adequate.
The rotors can have any number of tweaks
to make them more effective,
and most of them have to do
with getting rid of that heat energy.
Some have a gap in the
middle to let air in.
Some have fins in this gap
to pull air in,
and some would have holes all around
so that they could let air in and out
all over the place.
Your car’s brakes probably
won’t get above 400 degrees,
which is still super hot.
That would cook a pizza in 50 seconds.
– Pizza?
– Most pads are made of
semi-metallic material,
synthetics mixed with
difference proportions
of flaked metals.
Race disk brakes can reach
temps over 1,000 degrees.
So race pads are composed
of sintered steel
without any synthetic additives.
They work best at high temperature
because the demand on them is so high.
If you put them on your daily,
they’re gonna squeal like heck.
Just ask Tony.
It’s adorable, right?
He’s got his headphones on.
If your brakes squeal,
that usually means your almost out of pad.
Manufacturers put an indicator in them.
So they shriek like banshee.
Even if it turns out that
that’s not the issue,
squealing brakes mean
something is not right.
They could be vibrating
and not lined up right,
or maybe some foreign matter got in there.
And that can cause pretty
big damage in the long run.
Ever since we started going fast,
we had to look for better ways to stop.
We’ve come a long way
from just smashing wood on wheels.
So appreciate your brakes
because they keep you from being dead.
Okay, I guess it’s time to put a stop
to this episode of Science Garage.
No one wrote that.
Thanks to Skillshare for
sponsoring this episode.
Look, if you’re watching Science
Garage, you like learning.
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You wanna make cool motion
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Well, they got courses for that.
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So go to
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Go get skilled, get Skillshare.
Guys, thanks for talking with me today
about how brakes work.
If you guys wanna know
some of the best modification
you can do your own car,
check out this vid from Tony.
If you guys wanna know
other stuff about safety,
check out this video about helmets.
Guys just another reminder,
we’ve got merchandise.
Do you guys like this shirt
or you want a sticker?
Go to
We do a lot of fun stuff.
If you wanna see more of it, guys,
follow us on Instagram @donutmedia.
You follow me at Instagram @bidsbarto.
I love reading your comments.
I love talking to you guys.
Thanks for watching.
Don’t tell my wife I took her brakes.
It’ll be on tomorrow.
(cheerful music)

100 Replies to “BRAKES: How They Work | Science Garage”

  1. The basic theory of friction is force x coefficient of friction = friction force
    No where in there is area.
    Explain yourself B A R T

  2. an object is moving, it need's to stop moving ya'll still using brakes? Why don't you just stop moving? #madlad

  3. 3:17 "A greater surface area means more friction." That's actually not exactly true. Friction depends only on the normal force and the friction coefficient between the two materials, that's it; perhaps he meant to say that increasing the surface area can increase the normal force which would thereby increase the friction.

  4. Kinetic energy? Is that how it's spelt in the US or something? Don't know if I should trust these vids anymore

  5. If front wheel brake do 70%job done than why does bigger vehicles like trucks and dumpers have small brake drums,pads,piston etc infront wheels and bigger in the rear wheel

  6. What about regenerative braking, converts back to electrical energy? Oh wait thats electric trains sorry…..

  7. One important thing you missed is that stopping distance is effected by breaks, tires and weight

  8. 5:20 how does 400° cook a pizza in 50 seconds when my oven takes 12-18 minutes?! Should I be making my pizza on my rotors?!

  9. I was waiting to learn how brakes work. I guess I'll wait for another episode with that info. Until then, wish me luck!!

  10. Hey Science Garage, can you explain how regenerative brakes work? I have a BMW 328i and the manual says braking for longer is better than shorter distances, for energy recuperation. Also, it'd be nice to know why an engine at standby at a stoplight is better economy savings. Heck why don't you do a science garage on Hybrid Car's energy efficient qualities and characteristics!

  11. What the fuk? At first i thought “alright guys got it’s a bit much” now i cant get enough. I saw car with a donut sticker. 😃😃

  12. Rookie question. On disc brakes I understand how everything works with the floating caliper applying even pressure through hydraulics to both sides of the disc. My question is what causes the pads to retract? I see guys replacing pads and squeezing them right up to the disc. I know the piston applies the pressure for squeezing but what backs them off? I know they are extremely close to the rotor when no pressure is being applied so I'm guessing that the when the floating caliper with the spring loaded pins backs off the pressure, it just leaves the pads riding extremely close to the rotor if not barely touching which is why you almost always hear contact on any vehicle (motorcycle etc.) when just spin the wheel or roll it, like on my motorcycle. Thanks in advance for anyone's help.

  13. Just a quick correction increasing the surface area does not increasing your breaking power. The equation for a friction force is F=μN (friction force=coefficient of friction*normal force). Normal force would be how hard your squeezing the diskbreak, coefficient of friction is how much friction the two materials have when rubbing together, which when multiplied together gives you your total friction force. Surface area does not matter because as you increase it your N is spread out over that area giving you less friction per square inch. The larger surface area helps because there is more area to disperse the heat, not because it gives you more friction.

  14. Love donut media and the crew, y'all have to explain brake shoes, maybe episode worthy "disc vs drum brakes"

    Edit: I feel like the my episode concept is more for hi/lo disc vs drums

  15. I had a buddy who had a 94 vw Jetta beater and we decided to drive through a steep canyon, we got caught in fog going down hill and I had to ride the brakes to avoid driving over the edge then suddenly there were no brakes, I was scared as fuck as I had to clutch brake to the bottom in the fog because again no brakes worst shit ever, I never drove that pile of shit like that ever again even though he did regularly

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