COILOVERS
FUNCTION
A coilover is an automobile suspension device. "Coilover" is short for "coil spring over shock". It consists of a shock absorber with a coil spring encircling it. The shock absorber and spring are assembled as a unit prior to installation, and are replaced as a unit when the shock absorber has leaked. This provides for optimal damping without torsional loads. Some coilovers allow adjustment of ride height and preload, using a simple threaded spring perch similar to a nut. More advanced adjustable coilover systems will use a threaded shock body, coupled with an adjustable lower mount for ride height adjustment, while an adjustment knob is used to adjust damping. Stiffness can be changed by switching the spring for one with a different spring rate.The coilover style of spring placement is a basic component of the MacPherson strut suspension system, which is distinguished from other arrangements by employing a particular design of anti-roll bar as a longitudinal constraint. This was the first widespread use of the coilover in automobile suspensions, but there are other designs. The word coilover should not be considered a synonym for the MacPherson strut arrangement.
Coilovers should not be confused with struts or independently mounted shock absorbers.
Coilover suspension systems have become a popular staple in the automotive aftermarket. Once limited to racing teams with the research and development budget to create performance parts, these suspension systems are now widely available from most online and retail aftermarket auto part merchants. There are 2 different types of coilovers, full coilovers and slip on coilovers. The full coilovers are matched up with a shock from the factory, while slip on coilovers are mostly just adjustable springs.
PROS
Cheaper than AIR. German JOM adjustable coilvers can be bought for as little as 500$.Just like AIR, coilovers have adjustible height. Unlike AIR, the lower you go the stiffer it gets.
Enhanced performance!
CONS
Making your car handle better isn't easy. Camber, caster, toe, roll centers, motion ratios-suddenly building a show car sounds like a pretty good idea. Aside from tires, your coilover shocks are the single most critical component to your car not handling like a turd.The adjustability of coilovers is a two-edged sword. You can tweak the setup and make it better, but it’s far easier to make it worse. You also need serious time to make these adjustments and test to compare what adjustments are better. Lots of people don’t put in the time to do this, especially if they aren’t going to be doing any track driving, and just install coilovers on their car and lower it. At that point, it’s a waste, because new dampers and springs could have done the same for much less money. The amount of people who can really put a set of full coilovers to use is rather small.
Coilover sleeves are also available, and these can be added to dampers to provide that lowering adjustability while still costing less than full coilovers. One very popular setup over the years for moderate to serious driving has been Koni’s yellow adjustable dampers, with Ground Control coilover sleeves. This type of combo also helped many people who couldn’t find a full kit for their car, though there are likely many more kits out there now.
However, it's the argument of function and performance that stands above all others, and while few are prepared to argue that purpose-built racing suspension will be outshined by air struts, Air Lift Performance has put together a video pitting their best against your typical coilover system.
sources:
http://oppositelock.kinja.com/air-suspension-vs-coilovers-1462964641
http://www.stanceworks.com/2013/11/air-lift-performance-air-vs-coilovers/
http://www.reddit.com/r/cars/comments/2wycih/pros_and_cons_of_getting_coilovers_over_standard/
http://forums.vwvortex.com/showthread.php?4443963-PRO-and-CONS-of-Coilovers-VS-SPRINGS-and-Struts
http://www.automotiveforums.com/t492427-some_pros_and_cons_on_coilovers.html
http://www.ehow.com/how-does_5010001_how-air-bag-suspension-works.html
https://en.wikipedia.org/wiki/Coilover
http://www.superstreetonline.com/how-to/chassis-suspension/sstp-1303-how-a-coilover-works/
http://www.audizine.com/forum/showthread.php/187898-Coilovers-vs-Springs-Pros-and-Cons
https://en.wikipedia.org/wiki/Air_suspension
http://www.autotrader.com/research/article/car-tips/212905/pros-and-cons-of-air-suspension.jsp
