# Talk:Brake

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## Scientifically Illiterate

The article is scientifically illiterate.

The argument about 4x kinetic energy allegedly requiring 4x longer braking distance is completely and woefully bogus. If we used that logic, we'd have to conclude that a car with 2x weight should have 2x braking distance for the very same reason (2x kinetic energy). This is, of course, complete nonsense. For a practical example, Ford Mustang SVT has 2x the mass of Lotus Elise, but both have virtually identical 60-0 braking distance. Why? Because how fast a certain amount of energy is dissipated not only depends on the amount, but also on the _rate_ at which it is dissipated.

Don't get me wrong though, 2x speed does mean 4x braking distance, but it has nothing to do with having to dissipate 4x more kinetic energy, as the article incorrectly claims. The theoretical braking distance `D` is determined by a simple high-school formula `D = v2*a/2`, where `v` is the initial speed and `a` is optimal (maximal) braking deceleration. This is why 2x speed means 4x braking distance. —Preceding unsigned comment added by Calligrapher (talkcontribs) 18:06, 4 November 2009 (UTC)

## Pictures???

Whoever wrote this article should have put some pictures in there to help with the better explanation of brakes generally and especially when trying to explain how a car brake works. —Preceding unsigned comment added by 220.239.112.108 (talkcontribs)

Welcome to Wikipedia. Wikipedia is a collaborative effort written by volunteers—people like you. Instead of saying what somebody else should have done with their free time, you might think about how you can help improve the quality of Wikipedia yourself. -- Coneslayer 14:49, 12 July 2006 (UTC)

## The Generalization is Missing

In general, a brake is for retarding and stopping motion. This article refers to specific type of brake, which is a Wheel Brake.

A brake can stop linear motion (as in a meglev vehicle) as well as circular motion. A brake can also be used in a stationary device, such as a crane, in which case its structure and operating principles are not much different than when it is used on a vehicle.. —Preceding unsigned comment added by Feweiss (talkcontribs) 05:41, 4 June 2009 (UTC)

## Wet Disc Brake

Looking forward to seeing an article on Wet_disc_brake. Photnart (talk) 12:08, 24 August 2009 (UTC).

Try looking under disc brake. Bigdumbdinosaur (talk) 22:27, 2 September 2009 (UTC)

## Poor quality article

This article is nearly worthless. There's no material about brakes in general—all I see are some vague references to transportation. The use of a brake to stop a moving object without regard to the type of object isn't presented at all. Also, "hypermiling" (man, I detest these made-up words) is completely out of context. Getting better fuel economy in a motor vehicle involves more than judicious brake usage.

If someone were to come here looking for information about brakes and how they are used, they would be understandably disappointed.

Bigdumbdinosaur (talk) 22:31, 2 September 2009 (UTC)

"This additional force is supplied by the vacuum generated by the running engine, but this force is greatly reduced when the engine is running at full throttle and the available vacuum is diminished.

Because of this, reports of unintended acceleration are often accompanied by complaints of failed or weakened brakes, as the high-revving engine is unable to provide enough vacuum to power the brake booster. This problem is exacerbated in vehicles equipped with automatic transmissions as the vehicle will automatically downshift upon application of the brakes, thereby further elevating engine RPM and reducing available braking power while increasing the engine's effective torque."

Does anyone has a source about this bullshit? The correct version as I know is something like this: The vacuum booster servo (which provides the power brakes) is connected to the intake manifold of the engine and vacuum actually INCREASES as the RPM increases. (because increase in RPM causes the cylinders to suck more air from the intake manifold, decreasing the pressure and increasing the vacuum) That is why power brakes fail after being used a few times after the engines stop(no cylinder motion = no vacuum) Andraxxus (talk) 21:36, 9 October 2010 (UTC)

Automatic transmission's case : — Preceding unsigned comment added by Skk146 (talkcontribs) 07:13, 25 May 2011 (UTC) Brake boost : The vaccum assisted braking in case of automatic transmissions, while braking, the down-shift happens automatically and this will "decrease" the rpm, but increase engine output torque. Thus, braking becomes difficult as it needs to oppose a greater engine torque output. — Preceding unsigned comment added by Skk146 (talkcontribs) 07:10, 25 May 2011 (UTC)

^ 'scuse me, but a downshift will increase the rpm ... besides which, downshifting doesn't "increase torque" if you don't have your foot on the throttle because the engine is being back-driven by the vehicle's momentum, not the other way around. The above statement is not reality-based. 210.22.142.82 (talk) 04:23, 17 June 2016 (UTC)

## Vehicle brake

Why does the Vehicle brake article exist? Shouldn't it be merged here? Brake is even "dedicated to various types of vehicular brakes" so it looks to me the two articles cover the same topic. Kendall-K1 (talk) 17:04, 23 October 2014 (UTC)

## Merger proposal

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.
The result of this discussion was to merge. Kendall-K1 (talk) 16:25, 19 May 2015 (UTC)

I propose that Vehicle brake be merged into Brake. It's completely unsourced, and I don't think it has anything this article doesn't. Kendall-K1 (talk) 23:31, 22 February 2015 (UTC)

• Support - "Brake" is currently a better article on vehicle brakes than "Vehicle brake". "Vehicle brake" can probably be split off from "Brake" later on when "Brake" is expanded further (maybe when more content on brakes for stationary machines and conveyors is added). Sincerely, SamBlob (talk) 13:37, 12 March 2015 (UTC)

The above discussion is closed. Please do not modify it. Subsequent comments should be made in a new section.

I went ahead with the merge. I simply added the new material, didn't try to edit it in. So there is now some redundancy in the "Types" section. I'll work on this later if no one else does. Kendall-K1 (talk) 16:45, 19 May 2015 (UTC)

## Definition

The very first line is incorrect. A brake does not "absorb" anything. It changes one form of energy into another - in this case, momentum into heat. It would be possible to absorb the energy - flywheel systems have been built which do this - but a brake, as the term is commonly used and used later in this article, does not. 210.22.142.82 (talk) 04:29, 17 June 2016 (UTC)

This edit by Kendall-K1 made the text match the source, which says that brakes absorb energy. The source goes on to say that automobile brakes, typically frictional brakes, convert the absorbed energy into heat. But this article is about all types of brakes, including air brakes , electromagnetic, pumping brakes, regenerative brakes and kinetic energy recovery systems. I don't know why you say the article only uses the term to refer to frictional brakes that convert motion to heat. It does say that they are the most common and familiar type, but significant space is given to mentioning that there are other types. --Dennis Bratland (talk) 06:13, 17 June 2016 (UTC)
I have no problem with the "absorb" definition in the first sentence, since the article goes on to expand on this. If you have another source that gives a better definition I'd be glad to look at it. Kendall-K1 (talk) 14:36, 17 June 2016 (UTC)