Coilover Buyer’s Guide For Classic Trucks

Everything You Need To Know About Coilovers For Your Classic Truck With Aldan American

By Ron Ceridono   –   Photography Courtesy of Aldan American & The Hot Rod Library

02 These are Aldan single-adjustable coilovers
These are Aldan single-adjustable coilovers. The spanner wrench is used to adjust the spring’s preload, the bushings in the shocks are for ½-inch bolts, the four bushings on the right are for 5/8-inch bolts.

Of all the improvements made to a classic truck, suspension upgrades are arguably the most beneficial. There are a number of reasons for making suspension changes, not the least of which is what was expected from these trucks when they were new—trucks were designed to be tough, haul a load, and little else mattered. Today what we expect is a smooth ride, improved handling characteristics, and, more often than not, a lower profile. One of the most popular methods of achieving all those goals is with the installation of aftermarket coilovers.

03 Here are some of Aldan_s double-adjustable coilovers
This is a double-adjustable Aldan coilover: the top knob (arrow 1) is for rebound adjustment, the bottom knob (arrow 2) is for compression adjustment.
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What are the benefits of coilovers?

Compared to OEM suspension components (coil or leaf springs with separate shock absorbers), coilovers are compact and allow optimizing the spring rate by changing the easily replaceable coils. In addition, altering ride height can be done by turning the threaded adjuster on the shock absorber body, which changes the preload on the springs.

04 Jaguar_s Independent Rear Suspension early coilover suspension
OK so it’s not impressive looking in stock form, but the Jag Independent Rear Suspension helped make coilovers popular. Two of the four coilovers are visible through holes in the factory mounting cage.

Read More: 1969 C10 Front Suspension Overhaul

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Initial Introduction Of Coilovers

Coilovers have been around for a while. They began showing up on race cars in the ’50s and ’60s, but what caught the attention of many hot rodders was the use of four coilovers on the independent rear suspension of Jaguar’s XKEs introduced in 1961. Subsequently, there were many attempts at using coilovers on custom Independent Rear Suspension and solid axle installations, but the problem was in those days there were few options in coilover length, spring rate, or damping rates, but all that has changed. Aldan American offers coilovers in a variety of extended lengths, from 11 to 19 3/4 inches, three different damping options, and spring rates from 100 to 800 lb/in.

05 C-notched rear suspension provides adequate suspension travel
To allow this Chevy pickup to be in the weeds, Aldan’s Gary Nelson C-notched the rear frame rails to provide adequate suspension travel.

Aldan American Suspension

Aldan American has been a leading manufacturer of shock absorbers and coilovers since 1981. Their shock absorbers are CNC machined from aircraft-grade 6061-T6 billet aluminum. This process makes them incredibly strong and ultra lightweight when compared to forged steel shocks. For longevity, Aldan shocks use low-friction Viton seals and O-rings and the shock’s shafts are heat-treated, chromed, and finish ground before final assembly to reduce seal friction. Aldan offers shock absorbers with a variety of damping options that include fixed valves, single adjustable that allow compression or rebound rates to be tuned, and double adjustable that provide tuning of both functions with 66 independent settings. Shocks for coilover applications have threaded bodies to accept the adjustable retainer used to set preload on the springs.

06 We add Aldan Coilover mounts to the frame and axle housing
With the ride height determined, Nelson added coilover mounts to the frame and axle housing. The shock brackets were welded on at the midpoint of suspension travel with the mounting bolts parallel. A length of tubing takes the place of the coilovers during fabrication.
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How do I know what size coilovers I need?

To select the proper-length coilover for any application, measure the distance between the upper and lower mounting points with the chassis at ride height. Then simply select a coilover with open and closed dimensions that will fit with two-thirds of the shaft out of the shock body.

Here is what happens when the coilover mounting bolts are not parallel. These bolts were not aligned properly. As a result the shock bushings were destroyed (arrows) in a very few miles and the shaft of one shock was bent.

Before choosing coilover springs there are some terms that you should be familiar with: vehicle weight, as the name implies this is the total of everything from the ground up; sprung weight, which is supported by the springs; unsprung weight, that not supported by the suspension (wheels and tires, brakes axle housing); and half the components attached to the axle from the chassis (four-bars, Panhard bar, and so on). Another important term to be familiar with is spring rate, which is the amount of weight required to deflect a spring 1 inch. The lower the spring rate, the softer the spring.

08 Some billet aluminum shocks from Aldan American
This rack is full of Aldan billet aluminum shock bodies. Those destined to be coilovers will have threads to accommodate the spring preload adjusters.

How To Calculate Sprung Weight vs Unsprung Weight

When selecting springs the best method is to axle weight the vehicle then calculate the unsprung weight—this is the hard part, so you may have to guess. A typical 9-inch rear end assembly tips the scales at just under 200 pounds, and although wheels and tires vary greatly, published shipping weights may be available.

Read More: Affordable Coilovers For F-100 Crown Vic Front Suspension Swap

09 Aldan has several option for coilover mounting options
Aldan offers several coilover mounting options, including polyurethane bushings, spherical bearings, crossbars, and more. Polyurethane bushings isolate noise and vibration, spherical bearings are more forgiving of misaligned mounts.

How To Pick The Right Spring Rate

Once the unsprung weight is determined, subtract that from the axle weight then divide that number by two and you have the sprung weight. As an example, if a truck’s rear sprung weight is 1,400 pounds the weight on each rear spring is 700 pounds. Divide 700 by 2.5 (the constant Aldan recommends) and the result indicates 280-pound springs are appropriate.

10 Aldan coil springs are powdercoated or polished
Aldan coilover springs are available in long-lasting black powdercoat or a polished hard chrome finish.

How does shock angle affect spring rate?

Another consideration when selecting coilover springs is the mounting angle. The greater the installed angle, the stiffer the spring rate must be to support the same weight. Aldan uses the following mounting angle correction factors:

10°…………………………………..  0.98
15°…………………………………..  0.93
20°………………………………….   0.88
25°………………………………….   0.82
30°………………………………….   0.75

That means coilovers that would require 300-pound springs using our original calculations would require 400-pound springs when mounted at a 30-degree angle.

With the coilovers installed all that’s left to do is make any adjustments necessary. Obviously there’s nothing to do with non-adjustable shocks, fortunately Aldan’s valving works well in most applications. 

11 Here is how Aldan coilovers are assembled
To begin assembling coilovers the shock is held upside down in a vise (use plastic protectors or something similar to prevent damage to the shock body) then copper based antiseize is applied to the threads.

How To Adjust Coilover Rebound

On rebound adjustable shocks there are 11 settings, Aldan’s Gary Nelson will often start with three clicks clockwise from the softest setting as a starting point. From there adjustments can be fine-tuned as required.

12 The coilover is then dropped over the shock absorber body
Next the coil spring is dropped over the shock body, making sure it seats properly in the upper retainer (the end in the vise).

How To Adjust Coilover Compression

For compression adjustments Nelson suggests starting on setting number one of the six positions available and then making further adjustments as necessary. Be aware the compression knob doesn’t have a stop and will rotate 360 degrees. As the adjuster is a barrel valve, if the knob is rotated past six it returns to position one.

13 The spring is held in play by adjustable lower retainer
With the spring in place the adjustable lower retainer is installed. You’ll see there is a raised part that faces the spring and fits inside the coil.

Read More: Making A Canyon Carving C10: Big Brake Kit & Suspension Upgrades

When it comes to suspensions, Aldan coilovers tick all the boxes on the classic truck performance wish list: they provide excellent ride and handling characteristics, the spring rate can easily be changed, and ride height can be adjusted. What else could you ask for?

14 The adjustable collar acts as the spring seat allowing you to compress the spring
While holding the shock body, the adjustable spring seat is tightened to begin compressing the spring the specified 1 inch.
15 In this case our 12-inch spring was compressed 1 inch to establish the proper preload and spring rate
In this case our 12-inch spring was compressed 1 inch to establish the proper preload and spring rate.
16 Install an Allen setscrew in the adjuster, however don’t tighten the screw until final ride height is achieved
Install an Allen setscrew in the adjuster, however don’t tighten the screw until final ride height is achieved. The set screw has a yellow “locking compound patch” to keep the screw from backing out.
17 Full counterclockwise is the lowest setting, turning the dial clockwise increases rebound stiffness.
The top knob adjusts rebound. Full counterclockwise is the lowest setting, turning the dial clockwise increases rebound stiffness.
18 Compression adjustments have six numbered settings, the higher the number the stiffer the compression damping becomes
Compression adjustments have six numbered settings, the higher the number the stiffer the compression damping becomes. The knob is held in place with a slotted screw.
19 If it’s necessary to remove the compression knob there are two dots to align the number 1 position
If it’s necessary to remove the compression knob there are two dots to align the number 1 position
20 Coilover mounting bolts should always be front to rear to allow articulation during suspension movement
Coilover mounting bolts should always be front to rear to allow articulation during suspension movement. Bolts 90 degrees to the centerline of the chassis will cause binding and eventually break the shock mounts or the shock itself.
21 Coilover suspensions require some sort of lateral locator, the most common is a Panhard bar.
Coilover suspensions require some sort of lateral locator, the most common is a Panhard bar. Ideally the mounting points should be level, but Nelson points out that’s not always possible. With a long bar such as this, side-to-side movement will be negligible.

Source

Aldan American
(310) 384-7478
aldanamerican.com

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