Talk:Air suspension

Merger proposal
It seems to be that from an engineering point of view these two articles cover the same subject. (Both use 'air' as the spring material. And so should be merged, keeping the specific details of the citroen system etc in subsections.. —Preceding unsigned comment added by 87.102.77.78 (talk) 12:56, 4 January 2009 (UTC)

The two systems are in fact very different in both the springing medium and method of control I think merging the two would be detrimental to the specific information.Maybe a link notation from one to the other would be best. If I haven't understood the proposal fully please forgive me as I have only just started to contribute (Clampyoz (talk) 23:06, 6 February 2009 (UTC))

There is a vital difference between the two systems: the hydropneumatic system uses a constant mass of gas as the spring, whereas air suspension uses a variable mass of gas. The hydropneumatic system is thus capable of maintaining a constant spring rate, whereas air suspension can not. A constant spring rate translates roughly to a constant "feel" of suspension. If the two articles are to be merged into one, then this point should be discussed/explored; for it is one key advantage of the hydropneumatic system. 194.98.34.59 (talk) 15:27, 25 February 2009 (UTC)

Yes, there is quite a difference. Air suspension, which is commonly used on commercial trucks, on some cars - I know all lincolns and at least some mercury cars use a self leveling air suspension in the rear, and on modified cars like lowriders and hotrods, controls suspension height by adding or subtracting air from a rubber bag; while hydropneumatic suspensions - used by Citroen, and used on several newer armored vehicles, are controlled by adding or subtracting oil. While both actually increase the spring rate when the working fluid is added to counteract additional load on the vehicle - such as more passengers or loading up the truck bed - the key difference is this: With an air suspension, changing the ride height of the vehicle for reasons other than a changing load, such as riding higher off road, lower at speed, or whatever - changes the spring rate; while changing the ride height of a vehicle with hydropneumatic suspension does not change the spring rate if the load is not altered - meaning such a vehicle can be raised or lowered without affecting the spring rate.

The major drawback to an air suspension is that if the driver wishes to lower the vehicle, the spring rate will be reduced, all else being equal, where as it doesn't change with a hydrodynamic suspension. In either case, adding additional load will automatically increase the spring rate. Air springs work well for trucks, because the trucks have an air compressor anyway to operate the brakes, and the reason for air springs is to adjust to changing load conditions, while keeping the truck level, and the ride height is not really intended to ever change. People use air springs on hot rods and such to achieve a certain "look" - to the extent that the air is frequently let out when parking, because is is popularly considered to be aesthetically pleasing to park "in the weeds". A Citroen, as mentioned in the article, can be lowered at high speeds to increase efficiency without reducing the spring rate which would be detrimental to performance. And armored vehicles can be lowered to reduce their silouette, or one end or the other can be adjusted to "crouch" or "kneel" which can make it possible for a tank to fire up or down a hill, or at a helicopter. —Preceding unsigned comment added by 76.202.21.223 (talk) 13:35, 17 March 2009 (UTC)

In fact the two systems are significantly distinct, most notably in their design and what gasses they are using to create the damping and shock absorbing effects. Airbags use compressed air blown into a polymer bladder, sometimes the bladder is surrounding a shock tube, though this is less common. Hydro-pneumatic systems use a spherical reservoir affixed to the female end of the shock tube that is divided in twain by a polymer membrane with a determined flexibility. On the one side of the membrane is the shock fluid which is compressed by the shock ram into the lower surface of the membrane. As the fluid displaced moves the membrane upwards, it thereby compresses the gas contained therein. The current standard in the Citroen design, which was to my knowledge the earliest designed hydro-pneumatic system, is to use nitrogen gas that is permanently contained in the reservoir tank at a fixed pressure, unlike airbags. Where airbags create their damping and shock absorbency using air being kept at a set pressure regulated by either a computer or an operator, the hydro-pneumatic system creates the shock absorbency and variable ride height using the fluid, and the gas-fluid membrane creates the damping. —Preceding unsigned comment added by 140.160.122.21 (talk) 04:29, 18 March 2009 (UTC)

I see no evidence that we have discovered a usable common thread we can use to tie together Air suspension, Hydropneumatic suspension, Hydragas suspension, etc. - they are all defined by what they are not: steel springs. The complexity in combining stems from the fact that the features/benefits of one don't always overlap with the other, so you can't really take say "Self-leveling suspension" and make it a much longer article that explains all means to that end in detail. Since hydropneumatic suspension predates air suspension, a merger of "hydro" into "air" is especially off track. An article entitled 'Automobile Suspensions not using steel springs' seems rather ill defined - but it might work as a small subsection in Suspension - linking to a more comprehensive look - which has already been written. You can't merge these articles as it stands. 76.168.239.173 (talk) 21:25, 9 August 2009 (UTC)

Regardless of the engineering issues, the Citroen system is too important historically to be merged with anything. It deserves a distinct treatment. Tp11235 (talk) 17:51, 16 January 2010 (UTC)

Merging these two topics on the basis that they both use 'air' as the spring material is the equivalent of merging Leaf_spring and Coil_spring because they are both made of steel. Hydropneumatic suspension is a fundamentally different concept to air suspension and merging the two will lead to confusion and a single document that is harder to read that 2 separate ones. Noisymime (talk) 03:36, 5 February 2010 (UTC)

why is it being narrowed down to automotive application? i ve been redirected from "air spring" to "air suspension", wheres the subject in fact is broader, for example industrial applications etc, look eg. http://www.pronal.com.au/products/lifting.asp  —Preceding unsigned comment added by 201.19.239.205 (talk) 10:47, 13 February 2010 (UTC)

OK to remove the merger proposal? 76.170.227.101 (talk) 06:50, 27 March 2010 (UTC)

I seems to me that this article's purpose is less to discuss hydraulic suspension that it is to discuss Citroen's use of hydraulics. Hydraulic Citroens use a central hydraulic system which powers brakes, steering, suspension and in some models the gearbox. This article addresses this complexity without really addressing hydraulic suspensions. The Citroen hydraulic suspension does indeed change spring rates as the weight of the vehicle increases. This is a result of increasing the pressure on the gas in the sphere.

What is truly unique about the Citroen hydraulic suspension is the use of hydraulics. It is entirely different from air suspension because the fluid is dampened as it enters the suspension sphere, both impact and rebound dampening are built into the sphere. Air suspension must rely on an associated shock absorber to achieve this function. Thus the Citroen design combines both the spring and shock into one component. And because the shock absorber is all metal (the rate is determined by the diameter of the orifice) the effectiveness of the shock remains constant regardless of the temperature (within the viscosity rating of the fluid).

This lent enormous advantage in difficult road conditions since conventional suspensions stop working as effectively as they did at the start, due to high temps making the shock seals less efficient.

The concept of being able to lower the car with hydraulic suspension, at speed, is merely that, a concept. It was not practiced by Citroen. Lowering the ride height effectively reduces the spring rate making the suspension softer. That is not desirable at high speeds. The 'normal' height of an hydraulic Citroen is determined by the factory. From their the ride and handling characteristics are determined by the sphere charge pressure and shock absorber rate. There are additional variables such as cylinder diameter that can affect the ride characteristics. For example, with later Citroen CXs the cylinder diameter was modified to help stiffen the ride.

The hydraulic suspension is, in many ways, simpler and more reliable than conventional steel spring and shock absorber suspensions. But it has a penalty in that it draws power from the engine, either in mechanical ways (to run the high pressure pump on early cars) or because of electrical load (the high pressure pump is electrically driven in later cars). Assembly is also more complex than conventional suspensions. Additionally the cost is greater as there are more precision components involved (for example the high corrector valve has a 1 micron tolerance).

This entire article needs revision. —Preceding unsigned comment added by Pgrobin (talk • contribs) 00:56, 4 April 2010 (UTC)

Removing tag. Consensus was no merge. Tejanse (talk) 14:31, 30 October 2011 (UTC)

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Electronic Air Suspension
Is there any reason the article on Electronic Air Suspension shouldn't be a single paragraph in this article? There appears to be nothing unique or notable about it, and most of the contents are trivia about the particular implementation (like speed limits). Maury Markowitz (talk) 14:55, 4 April 2017 (UTC)
 * ✅ Klbrain (talk) 09:13, 6 October 2018 (UTC)

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dubious claim
"Air suspension is used in place of conventional steel springs"

In the large majority of cases, "air springs" are used in addition to,  not in place of, coil springs.Lathamibird (talk) 11:24, 9 November 2017 (UTC)

No the statement says "on passenger cars". Very few passenger cars have air suspension in addition to original suspension. Some commercial vehicle do have "semi-air" but numerical virtually all air suspension systems are the sole suspension - don't have figures to hand but something in the region of 60-80% of all buses and lorries. Those cars with air suspension its probably a higher %. Only aftermarket retro-fit conversions use both for the most part. — Preceding unsigned comment added by FabulousPhil (talk • contribs) 21:50, 9 November 2017 (UTC)

Wrong about years w/o it on the market
This thing had it, for the rear: https://en.wikipedia.org/wiki/File:1974_Mercury_Montego_MX_Villager.jpg

(give or take a year perhaps, and possibly subject to trim level... it is that generation of Mercury Montego station wagon though)

97.104.70.92 (talk) 04:58, 4 October 2018 (UTC)

Anonymous user advertising VB Air Suspension
An anonymous user has added the section and edited it. They are insistent on advertising VB air suspension on the section although it adds little to the information. Companies work in this way all the time - the system is not revolutionary, and the note adds nothing to knowledge. It is tracked to several IPs in VBs homeland and appears simply to be VB Air suspension adding entries to promote their company. FabulousPhil (talk) 08:54, 28 October 2019 (UTC) — Preceding unsigned comment added by FabulousPhil (talk • contribs) 08:43, 28 October 2019 (UTC)

The section also makes unsubstantiated claims which are incorrect regarding different types of air suspension. It is done in a manner which is clearly advertising material and would appear to be VB or their agents. FabulousPhil (talk) 08:54, 28 October 2019 (UTC) — Preceding unsigned comment added by FabulousPhil (talk • contribs) 08:47, 28 October 2019 (UTC)