Crown Victoria, Town Car, Grand Marquis, Front Position
Spring Rate: 650 lbs.
Shock Adjustability: 3-Way Adjustable
Shock Type: Mono Tube
What are Coilovers?
Coil over shocks are an “all in one” suspension system. Instead of a spring (be it leaf, coil, or torsion) to control ride height and a separate shock to control jounce and rebound the coilover shock features a shock body, often made of aluminum, with external threads either machined into the body or as a separate sleeve and a compact coil spring that surrounds the shock body and is retained by a spring seat and collar at the bottom and a spring hat or on chassis spring cup at the top. The coil spring’s rate is user defined and can be changed to support the chassis/engine’s weight. Furthermore, the coilover spring can be adjusted on the shock by raising or lowering the spring collar to raise or lower ride height. If equipped, the user can also adjust the coilover’s compression and/or rebound rates via adjustment knobs on the shock body. The coilover shock and spring assembly is often much easier to package than a separate spring and shock absorber, making for additional room to fit larger tires and saving on a vehicle’s unsprung weight. While using lowering springs will provide a fixed drop, they are not user adjustable, so when it comes to lowering springs vs coilovers, the coilover shock setup will always be the preferred route.
Which Mounting End do I Need?
Let us start with the mounting end types available. The end style will be dictated by your chassis and suspension pieces like control arms, axle housing, and so forth. There are three major end mounts: the eyelet mount, the T-bar mount, and the stud mount. The eyelet mount is essentially an open eye that a stud or bolt passes through. The T-bar mount is like an eyelet mount, but instead of a bolt or stud a fastening bar passes through the eye and the bar itself has two smaller holes for mounting bolts to secure the coilover shock end. Lastly there is the stud mount where the shock end is a threaded stud with bushings and washers that pass through a hole in the suspension component. Many rear coilovers are of the eyelet mount design on both ends, while the ever-popular Mustang II IFS usually uses a coilover with an eyelet on the bottom at the control arm and a stud mount at the frame. So, before you go any further, look at your frame and suspension pieces and make note of which ends your coilover shocks need to be before ordering.
How do I determine the Correct Coilover Length?
Once you have concluded the appropriate end mount style you will need for your coilovers your next step will be measuring for the proper coilover length. First you need to have your suspension installed and the vehicle at ride height (so it is best to have your wheel and tire package on hand or know the overall diameter of the wheels and tires you want to use and have something with the same specs for mock up). Once you have the ride height confirmed you can measure from the centerline of the upper shock mount to the centerline of the lower shock mount. This will give you the installed length, however, there is a bit more to this measurement. Taking that installed length measurement you can scan through our selection of universal adjustable coilovers, taking note of two additional measurements—the coilover shock’s compressed length and extended length. This info is found on each product page. You generally want about 60 percent of the shock shaft stroke in play at ride height. This will aid in preventing you from installing too long or too short of a coilover shock on your ride. The good news is we also provide mounting length data for every coilover shock as well, making your decision that much easier.
What is Spring Rate and Which Rate do I Use?
Spring rate is measured in pounds per inch and relates to how many pounds it will take to compress the coil spring one inch. So, a 300-pound spring will compress one inch with 300 pounds of weight exerted against it; two inches with 600 pounds of force, and so forth. The coil diameter and number of coils are the primary driving factor of spring rates but generally you want the spring compressed about 30 percent of its free length. Knowing your vehicle’s front and rear weight is critical to ordering the correct spring rate for your ride. You will also need to correct for shock mounting angle, as the higher the mounting angle the less spring rate you will have for a given spring’s rating. For example, to obtain the same results as a 300-pound spring mounted straight up and down in a 20-degree mounting configuration you would have to increase the spring’s rate to 350 lbs. We do not have the room here to show all the math, but you can find spring rate charts all over the web and more in-depth details right in our own Toolbox section here. The critical things to know are your car’s front and rear weight and the angle, in degrees, of your coilover mounting points.
What Makes a Coilover “Adjustable?”
While coilover shocks are adjustable just by their vary design of capturing the spring on an adjustable spring seat with locking collar, we are in fact referring to single- and double-adjustable coilover shocks that allow you to adjust the rebound and compression together (single adjustable) or individually double adjustable). When you opt to upgrade from a fixed-valve coilover shock to a single- or double-adjustable coilover shock you are adding the ability to adjust the coilover shock even further via a single or pair of knobs directly mounted on the shock body. These knobs have detents, or “clicks” that they seat on, providing a specific number of adjustments. With a single-adjustable coilover shock the internal oil that is pressurized flows through a single orifice (the orifice size is what you are changing when you rotate the adjustment knob), thus you are making the same adjustment to both rebound and compression on the coilover shock. Essentially you can make the whole shock softer or stiffer. With a double-adjustable coilover shock you have even further control of the dampening by now being able to adjust the rebound and compression individually of each other. The internal oil passages are separated, allowing precise flow adjustments. So, whether it is drag racing, road racing, oval track, or just spirited street use, the individual adjustments allow quick, on car changes to counter track conditions and other variables. Let’s put it this way, if a single-adjustable shock has 12 settings, that’s all you get, but on a double-adjustable shock those 12 settings on compression and 12 settings on rebound now mean you have 144 total adjustment combinations! Taking the time to learn how to adjust coilovers will mean better handling, faster lap times, and an improved ride.
Updated By Mark Houlahan