Talk:Air brake (road vehicle)

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Some kind of nice graphic/picture might help build a mental picture of what's going on.

I agree (Pingualot 21:09, 8 June 2007 (UTC))

What about trucks?[edit]

The article seems to only talk about tractors. 01:09, 21 September 2007 (UTC)

    • The article talks about trucks or commercial vehicles in general, the unfortunate result is that number of editors who altered the original descriptions over the course of the time now make no sense and confuse the whole thing. It seems quite obvious that also those who've contributed have a very limited knowledge of the systems, like someone who decided to use the included "SIMPLE" diagram to make it as general description of common air systems found on heavy vehicles at present. Stonufka (talk) 10:07, 4 October 2008 (UTC)

Why? Section[edit]

The article, I think, does a great job of explaining what an air brake is and where its used, but not why Air Brakes exist.

Why, for instance, do heavy load units like trains and Prime Movers use Air Brakes instead of hydraulic? I think that'd be a good addition to the article (sadly, I don't know why they exist on trucks instead of hydraulic units, so I can't add it). Scryer_360 (talk) 23:10, 19 March 2009 (UTC)

The reason is simply heat dissipation and is the same reason that trucks most often use drum brakes instead of disc brakes; disc brakes can produce much more (around 2x) more braking force than drum brakes but are still just starting to be used in truck applications due to their inferior heat dissipation properties. Nofrendo (talk) 02:02, 31 May 2009 (UTC)

The statement about heat is completely backwards, it's about simplicity and brake force. Discs dissipate much more heat, thanks to being exposed fully (while the linings operate internally on a drum, and the drum itself needs to store and remove more heat than a disc of similar operating capacity would). There's more to why discs are better, and..they are.
Drum brakes, however, offer some degree of self-application in some cases (see the drum brake article on leading/trailing shoes) -- although most air drums are twin-leading.
Discs brakes require more precise manufacturer and materials in their production and application. And parking brakes have to be implemented -- I have yet to see one operating on an air disc itself, and I've been at this a good number of years now. Drum parking brakes are very simple, and most cars use a small parking drum inside of the disc brake itself to achieve the function. There's other problems, too. Discs brakes are inherently more complicated, even though looking at it -- they appear simple.
Air brakes can apply far more force than a similar hydraulic system, are more forgiving (small leaks don't compromise the entire system, contanimation is easier to remove, etc. -- unlike hydraulics), and are simpler than air/hydraulic systems. Hydraulic brakes with multiple master cylinders through multiple pneumatic boosters gets to be a real plumbing nightmare.
Hydraulic brake systems tend to be very sensitive about air or water in the system, and water evaporating (from the heat produced) causes a great deal of issues. However, they are more compact, do not require air-compressors or storage tanks, and are therefore quite common on smaller vehicles. On a truck, where space is less of an issue, it keeps it simpler.
The ease of plumbing is wonderful in trains and semi-tractors where the trailer (or train cars) need to be added to the braking system quick and easily. Two connections on a trailer and you have service and supply. The more complex pieces are contained in the tractor for safety, and the trailer has its relay valves and ABS system onboard.
There's also pneumatic suspensions -- having onboard air allows them to inflate/deflate themselves. Really, air is a far more versatile medium to work with than hydraulic fluid in most cases, and it lends itself wonderfully to brake systems on heavy vehicles. As for trains, I can only speak in deductions. (talk) 00:42, 3 November 2010 (UTC)

Another reasom, at least historically, that I read back in the late eighties, was that the manufacturers had not managed to devise a system which still worked "when a truck is up to its axles in crap". Mr Larrington (talk) 00:28, 7 October 2014 (UTC)


Is it worth adding a short section on the practice, and/or adjustment? It might be too practical to be useful in a wikipedia, but maybe just a description. (talk) 00:45, 3 November 2010 (UTC)

Separate truck brakes and air flaps[edit]

The term "air brakes" can be applied to both the truck brake technology, and the wing flaps found on some cars, but they really should be in separate articles, as they're almost entirely unrelated. Rather than including that section here, just because this article is about road vehicles, I'd suggest moving it into the aircraft section, with the title "Use in motor vehicles" instead. OpenBracket (talk) 17:42, 1 January 2011 (UTC)

Agreed. The current bumping together is ridiculous. Could anyonend a hand? (talk) 17:26, 22 March 2011 (UTC)


The following paragraph is incorrect:

Air line couplings are easier to attach and detach than hydraulic lines; there is no danger of letting air into hydraulic fluid. So air brake circuits of trailers can be attached and removed easily by operators with little training.

It should read: Air line couplings are easier to attach and detach than hydraulic lines; unlike with hydraulic brakes, there is no danger of letting air into hydraulic fluid. So air brake circuits of trailers can be attached and removed easily by operators with little training.