
Why Do Cars Have Brakes? - galaktor
http://www.devjoy.com/2013/02/why-do-cars-have-brakes/
======
adam-a
The premise is surely nonsense! The full logic ought to go: Why do we have
cars? To go faster. Why do cars have brakes? In order to slow down again.

If all we were concerned about was going fast then why ever slow down? Cars
need to regulate their speed in order to provide safety, and also so they are
usable, if I can't stop then I can't get out at my destination. Many elements
of a car help in it's overall function, which is to go fast, but you may as
well say the purpose of a fan belt is to go fast. Brakes are a part of a car
and saying that their purpose is the same as the whole car is useless and
confusing. They have a specific purpose within the machine.

From the linked article: "[the] answer feels paradoxical which usually means
there's a deep truth". Indeed. The simpler explanation is that it's pure
twaddle.

~~~
michaelt

      if I can't stop then I can't get out at my destination.
    

Different people seem to have different interpretations of this question. My
interpretation was: Why have brakes instead of coasting to a stop? Coasting to
a stop is popular with drivers who are 'Hypermiling' [1] - and bicycles used
in velodromes don't have brakes [2].

While this isn't consistent with Richard Dalton's blog post (if you coast to a
halt, you wouldn't need to throw your children out of a moving vehicle) but it
isn't inconsistent with Jon Jagger's blog post, which Dalton credited as his
inspiration.

[1] [http://en.wikipedia.org/wiki/Energy-
efficient_driving#Accele...](http://en.wikipedia.org/wiki/Energy-
efficient_driving#Acceleration_and_deceleration_.28braking.29) [2]
[http://en.wikipedia.org/wiki/Velodrome#Bicycles_and_track_de...](http://en.wikipedia.org/wiki/Velodrome#Bicycles_and_track_design)

------
ilcavero
I wonder if car technicians go around making weak analogies with software
development to justify their industry practices. Something like: "Why do
software developers have compilers? blah blah blah, and that's why we need to
keep your tools organized"

~~~
wikwocket
Why do computers have virus scanners? They only serve to slow down the
computer and to block some programs from running. This is contrary to the goal
of a computer, which is to run programs! But by blocking evil programs, the
good ones can run faster, with less disruption.

...and that is why we change our motor oil.

------
X-Istence
Has the art of using the engine to slow down become so unknown that it is no
longer considered a way to slow down a vehicle?

~~~
roel_v
Only works on stick shifts.

~~~
X-Istence
And every single last automatic. Besides D there is always a couple others,
like 1, 2, 3 that are used for getting out of sticky situation or when you
need a lot of torque... those also apply for engine braking.

Do I suggest engine braking in an automatic in the general case? No, generally
because the torque converter isn't too happy unless it was specifically
designed for it. However if you are going down a steep mountain you better
downshift even in an automatic and use the engine, or when you get to the
bottom your rotors will be glowing red, your brake pads will be disintegrated,
your brake fluid will be boiling and your car will be smelled from miles away.

Yes, I have seen people brake all the way down the I-70 coming over the vail
pass in Colorado, and it isn't pretty... if it doesn't break everything your
rotors are going to be warped completely...

~~~
luser001
Kids, listen to this man. :)

When I was newbie, I didn't downshift and was instead keeping the brakes
lightly pressed. After a few mins of this, when I pressed them a little harder
to slow down more (at a turn), the pedals sickeningly went _way_ more than
they were supposed to. Remembered in a flash what had happend. Thankfully, I
was able to pull over and let the brakes cool a bit.

The brake fluid had overheated and turned into a compressible liquid (if you
remember your Pascal's Law (iirc), hydraulics can only work if the fluid is
nearly incompressible).

~~~
X-Istence
Eh, I'm 24 years old ... in the crowd here on HN I would be considered part of
that "kids" :P

------
bazzargh
Overextending the analogy, there's no brakes on track bikes but they go fast
too. They don't need them, the fixed gear means applying counter pressure on
the pedals stops the bike.

The clunky software analogy would be to do with lightweight simplicity.

------
brudgers
The analogy between automobiles and software testing can be extended to
consider the racing line - the combination of velocity and distance through a
corner which results in the fastest time.

<http://en.wikipedia.org/wiki/Racing_line>

~~~
makira
Which brings me to the point that the steering wheel is much more important
than brakes. Being able to go faster because of brakes is not very useful if
you are heading into a wall.

~~~
ygra
Well, you can still stop before hitting that wall. Steering might be of little
use if you're going fast and approaching a dead end with walls on either side.

~~~
ottbot
Perhaps we've driven beyond the metaphor.

------
ynniv
Wow, a silly brain teaser AND a strained metaphor. I'll never hear the end of
this one!

------
lazyant
Even my parody "Ten Reasons Why Building a Startup is Like Riding a
Motorcycle" has more meat than this :-)
[http://lazyant.com/post/37406994081/ten-reasons-why-
building...](http://lazyant.com/post/37406994081/ten-reasons-why-building-a-
startup-is-like-riding-a)

------
AUmrysh
When I was on my company's R&D team, we were looking at possibly designing a
car. One of our ideas was regenerative braking (nothing new, I admit).
Basically, you can use several types of pump or motor as a generator when run
in reverse. This allows you to collect that energy back into the system
instead of wasting it all as heat. It also has the added benefit of turning
the rotational kinetic energy into stored potential energy, thereby slowing
down the vehicle. Our design still included disc brakes for safety, but would
have used the regenerative braking most of the time.

------
rdtsc
To really add breaks where you can stop while running without blowing
completely up you need to add fault isolation and tolerance in your system.
You need to use actors and messages (you might get parallel execution as well
depending on your algorithm as a bonus).

The alternative is to prove that your program won't crash. So you need to
write in a very restrictive style. This is more like you need to be able to
compute a path your car will take ahead of time given all the other obstacles
that could get in its way. That works too but it is highly impractical.

------
codeulike
Why dont the lightcycles in Tron have brakes would be a better question.

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monochromatic
I drove a motor scooter as a kid that had broken brakes. He's right--it wasn't
much fun, because I knew I couldn't go fast.

~~~
barrkel
And by extension, my scooter has ABS brakes, which means I can go faster in
the wet.

------
digitalWestie
If people knew how to drive efficiently they'd use gears to do this and only
use brakes to stop. Just sayin'

~~~
Toucan
How would that be efficient?

Engine braking wears transmission components which are considerably more
fragile and expensive than replacing brakes. Engine braking only stops you
using the driven wheels, brake discs apply to all wheels.

~~~
ferongr
>Engine braking wears transmission components

No it doesn't. Synchronized, rev-matched downshifts put negligible load on the
drivetrain. Coasting to a stop with the gear already selected, putting it in
neutral just before stall does that even less. The stresses produced by
acceleration are ballpark estimate around an order of magnitude greater. This
can be inferred by the fact that usually the rate of deceleration by engine
braking is smaller than the rate of acceleration for a given gear ratio, ergo,
the drivetrain is strained less.

~~~
Toucan
It still wear components that are not as easily replacable as brakes. As for
coasting to a stop whilst still in gear, I agree with that being a good idea
but I don't think that's what digitalWestie was getting at.

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abraininavat
This is ridiculous. The typical "stoner effect" -- a phrase that sounds in
some way deep or metaphysical causing susceptible people's neurons to flare,
producing only the word: "Woah..." I know this is probably controversial, but
in my opinion it's the same effect that causes people to find deep meaning in
a Jackson Pollock painting.

As others have pointed out, lots of fast things don't have brakes, because
they don't need to stop. As I don't think others have pointed out, slow things
have brakes too, such as the space shuttle transporter.

~~~
SatvikBeri
You're certainly right in that there are logical flaws in the article. But the
stoner effect is useful (and dangerous) because it's much better at creating
changes in beliefs/behavior than rational argument. It's a pattern worth
understanding because you can use your understanding to defend yourself, or
use parts of the effect to communicate your ideas and convince others.

The book _Switch_ [1] goes into more detail about what actually works when
you're trying to get people to change. I highly recommend it if you're
interested in Psychology or Marketing.

[1]: [http://www.amazon.com/Switch-Change-Things-When-
Hard/dp/0385...](http://www.amazon.com/Switch-Change-Things-When-
Hard/dp/0385528752/)

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atc
What a load of shit.

~~~
robotic
analogies gone wrong -- terribly wrong

