A coilover 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 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 use a threaded shock body, along 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.
Two of the main types of coilovers are full coilovers and slip on coilovers. Full coilovers are matched up with a shock from the factory, while with slip on coilovers, the dampers and springs are bought separately and then assembled.
Coilovers are found on many vehicles, from RC cars to normal passenger cars, race cars and 4x4 vehicles. They are sometimes used as a factory suspension option on new cars. Many aftermarket companies also make coilovers for vehicles, many of which allow the customer to adjust various settings such as ride height, damping, rebound and camber angle. This high level of adjustment is what gives coilovers an advantage over a typical MacPherson strut.
Coilovers can be used to lower the center of gravity of the vehicle to reduce weight transfer when the vehicle is going through turns at high speeds.
Coilovers are made up of several components, including the shock absorber, coil spring, bushings, bumpstop, upper and lower mount, jam nuts, various nuts and washers, threaded sleeve and collars.
For adjustable coilovers the bottom mount is a threaded sleeve that will have two adjuster nuts. The adjuster nuts are used to preload the coil to increase or decrease the vehicles ride height. To do so a spanning wrench is needed to. The wrenches are grooved C shape bars that grip the adjuster nuts used to break the seal on the threaded sleeve and can be adjusted.
Mono-tube vs. Twin-tube
A mono-tube coilover is a single piston and rod assembly in a damping case where compression and rebound both occur. A larger mono-tube shock will be able to displace more hydraulic fluid, providing a more sensitive response time to small suspension movements than twin-tube shocks.
A twin-tube coilover has more mechanics to it. Twin-tubes have an inner cylinder moves up and down and an outer cylinder which serves as a hydraulic reserve. Allowing for an increase in piston stroke which provides a better ride quality and handling.
Compression & Rebound
There are three type of damping adjustability; manufacturer, single, and double adjustable. Manufacturer coilovers are pre-set to what the manufacturer believes car owners need. These coilovers are valved to the springs they are paired with. Compression is the piston in the shock moves into the body controlling the vehicles un-sprung weight. Rebound is when it pulls away from the body which controls the motion of its sprung weight.
The springs purpose in a coilover absorbs bumps as well as controlling body roll. Their purpose is to prevent the chassis from bottoming out, supports each individual wheel on the vehicle, as well as maintain body roll when going into turns or cornering. The springs on coilovers also help control squatting when accelerating as well as reducing the vehicle from diving when the brakes are applied. The springs also can set the vehicles ride height which directly affects handling.
Preloading is the amount of set pressure applied to the springs setting how far they are to be compressed. Preloading is required to help improve mechanical grip to improve wheel contact when turning; however excessive amounts can damage your performance. A known issue with slip-fit coilovers and full-bodied coilovers is they are not adjustable on the lower mounts; however, ride height is adjusted through preloading the spring itself.
- Steve Hendrickson Gerry Burger. Hot Rodder's Bible : The Ultimate Guide to Building Your Dream Machine. MotorBooks International. pp. 179–. ISBN 978-1-61060-963-0.
- Keith Tanner (2 December 2010). How to Build a High-Performance Mazda Miata MX-5. Motorbooks. pp. 113–. ISBN 978-1-61060-970-8.
- Julian Happian-Smith (2001). An Introduction to Modern Vehicle Design. Elsevier. pp. 285–. ISBN 978-0-7506-5044-1.
- Tim Gilles (2005). Automotive Chassis: Brakes, Suspension, and Steering. Cengage Learning. pp. 329–. ISBN 1-4018-5630-6.
- "Coilovers vs Springs – What are coilovers and what's better?". www.aptuned.com. Retrieved 2018-06-10.
- Team, Low Offset (2018-06-05). "Coilovers vs Lowering Springs: Which is Better?". Low Offset. Retrieved 2019-01-11.
- "schoolphysics ::Welcome::". www.schoolphysics.co.uk. Retrieved 2019-01-11.
- "How A Coilover Works - Super Street Magazine". SuperStreetOnline. 2013-04-09. Retrieved 2018-04-25.
- "How A Coilover Works - Super Street Magazine". SuperStreetOnline. 2013-04-09. Retrieved 2019-02-14.
- http://www.pirate4x4.com/tech/billavista/coilovers/Part_1/, in-depth explanation of coilovers and their function.
- http://www.corbymotorsport.com/tuning_guide.php, article related to setting up coilovers
- http://accutuneoffroad.com/articles/shock-tuning-101/, how to tune rebuildable coilovers