The How, Why, and Where Guide to Suspension - Up Or Down
The How, Why, And Where Guide To Suspension
From the December, 2004 issue of Sport Truck
By Sport Truck Staff
Photography by The Sport Truck Archives
Static lowering (nonadjustable) has been around about as long as cars have been on the road. The first lows probably came from a grease monkey and his oxygen/acetylene torch heating the spring and letting it collapse. Then it moved onto pulling the spring out and lopping off a coil or two. Well, both of these methods worked, but, man, the ride quality went in the toilet. Thank goodness the aftermarket world came to our rescue with reengineered springs, drop spindles, and drop-pocket control arms to bring down the front of our trucks. Out back, you can expect to use blocks, short shackles, raised hangers, lighter springs, or a flip kit. Blocks can be used if the axle is over the spring pack; if not, look for a flip kit that will position it that way. A flip kit usually drops the truck about 6 inches, so if you're looking for something less, using a combination of short shackles, springs, or hangers will get you where you want your back to be.
When it comes to lifting a truck, the type of lift will depend on the specific model, but for the most part, lift kits now consist of drop-down brackets. These move the mounting points of the lower suspension components down. Then, an extended spindle will take up the added space created between the upper and lower arms. For some of the earlier trucks, all that's offered are longer springs and new control arms that are installed to keep the alignment true. Some trucks can also benefit from a basic lift spindle. To raise the back, you will be looking at extended shackles, new hangers, or new leaf springs. If you're looking for a smaller lift, there are cost-effective spring spacers and lift blocks that can add an inch or so without busting your budget.
That is just a quick breakdown of what it takes to lift or lower your truck, but we thought, Why not go into more detail about the basic parts in a suspension system? Each of the following sections should give you a small primer on what they are and how they work. Then we put in a list that will hopefully point you in the right direction to get the parts you want to get up or down.
Coil Springs A coil spring...
A coil spring is constructed from round-bar stock wire that is wound or coiled in either a hot or cold procedure. Of course, the thickness of the round-bar stock and the amount of coils will determine the strength and rigidity of the coil spring. The coil spring winding is also a very important segment of the coil spring process; the distance between coils will dictate the spring rate. Spring load and spring rate are often misinterpreted. When we refer to spring load, we are taking about the amount of weight that will compress the spring to a specific height that is translated in pounds. Spring rate is the amount of weight applied to the spring to compress it 1 inch, which is expressed in pounds per inch. Remember that the spring rate will not change during the compression of the spring, but the spring load will.
Leaf Springs The other type,...
The other type, a leaf spring, is constructed of flat-bar stock. Its tapered thickness helps give it both strength and flexibility, and it's arched to create added strength and recoil action. To develop increased strength to the suspension, additional leaves can be added or stacked. Most leaf springs are made of SAE 5160 alloy steel.
Coilovers A coilover spring...
CoiloversA coilover spring is used in conjunction with a shock running through the center of the coil spring. The coil spring is then contained by two collars, one at the bottom of the shock and the other at the top. The adjusting collar at the top or bottom of the shock is threaded, along with the shock tube, while the other collar is fixed. By loosening or tightening the threaded collar, the ride height and spring load can be adjusted. Coilover shocks can be used in both the front and rear suspension.
Airbags One of the newer...
One of the newer components in the suspension world is airbags. They are a direct replacement for the coil springs or as a load-helping device. There are two components that make up a 'bag: the cap and the bellow. The cap is either constructed from steel or billet aluminum, with ports ranging from 3/8 to 3/4 inch for the air to get in. The bellow is made of varying-thickness rubber and a high-strength fabric in either a tapered-sleeve or convoluted design. Numerous styles, sizes, and capacity ratings are available. The air pressure in the air spring varies the load capacity and ride height. The air spring has certain design parameters that allow it to operate at maximum efficiency. These parameters are design, height, stroke, and load.
Antisway Bars The best way...
The best way to cure the truck's body roll (roll angle) is to install antisway bars both front and rear. Antisway bars effectively tie the left and right lower control arms to the framerails. The arms can still articulate up and down, but once you put the truck into a turn, the arms share the lean and keep the truck flat.
The effectiveness of an antisway bar depends on its length, as well as its diameter. The longer the swing-arm length, the less force the bar can provide with the same amount of movement at its ends. Another major contributing factor is the antisway bar's diameter (material girth equals strength). Also, the total stiffness of an antisway bar depends on the rigidity of the frame mounting points and endlinks.
Shocks The purpose of shock...
The purpose of shock absorbers is to control the compression, extension, and velocity of the truck's suspension. If the shocks don't have enough resistance, the spring will move the suspension too fast and it will have an underdampened motion. If the shocks are too firm, the motion will be overdampened. When the truck goes over a bump, the shock will compress; when the truck goes over a pothole, the shock will extend. The amount of time it takes to go back to its normal or static ride height is referred to as rebound. To help control the shock absorber's frequencies (movement of compression and extension), the shock body is filled with a hydraulic fluid (a petroleum-based oil) that is moved through a series of valves, and a single piston controls the shock travel.
As the truck's suspension is lowered, the amount of travel within the shock is also decreased, so this means you have to get a shorter shock or add extensions. When lifting a vehicle, you will have to purchase a longer shock with more throw to compensate for the added travel.
Spindles Spindles are a cast...
Spindles are a cast piece of steel with a machined spud sticking out upon which the wheelhub and bearings ride. They bolt between the upper and lower control arms and provide a place to mount the brakes and wheels. You can raise or lower your truck with the spindle. Many companies manufacture lift- or lowered-type units; moving the spud in relation to the center (distance between the ball joint mounts) will change ride height. If the spud is moved up, it will produce a lower ride height, and if it's lowered, the truck will go up. Raising or lowering with spindles will retain proper suspension geometry, so if you're looking for a couple inches, this might be the starting point. The only issue you might come in contact with on an aftermarket spindle is rim interference. When the spud is moved, the rotating assembly will get closer to the rim, so a larger-diameter rim and tire combo might be needed.
Control Arms (A-arms) Control...
Control Arms (A-arms)
Control arms (aka A-arms) are a triangular-shaped component used to hook the suspension to the chassis and allow it to pivot. They are made of stamped steel or cast aluminum, or fabricated from steel tubing. Aftermarket A-arms are used to either raise or lower a vehicle and maintain the ability to have your vehicle aligned by correcting ball joint geometry. Drop-pocket control arms are just that: The area where the spring rides on the arm is lowered, making the spring seem shorter.