In a four-link suspension, the axle can move up and down and articulate while being restrained from moving side to side and back to front. We must concur with the majority when they say that a four-link suspension with coils, coilovers, quarter-elliptics, or air springs is unquestionably cool, and it is the most typical justification for creating your own system. The issue emerges when you just start installing bars and links under your truck because you believe you know what you’re doing. Even though we have no issues with you making one just to give it a shot, just because you saw it on a race truck or rockcrawler doesn’t mean you need it for your weekend wheeler.
Running a four-link has certain undeniable advantages, but doing it properly requires time, money, and even more time and money. In order to provide you a realistic perspective of a straightforward rear four-link suspension, we will first discuss its advantages and disadvantages. You decide, but please think carefully before making a decision. It is nevertheless true that a well-designed and proven four-link suspension will offer better power transfer to the ground and a smoother ride than a leaf-sprung suspension. The testing section is where the secret lies. If you construct a four-link on your rig, be ready to modify it and disassemble it numerous times until it functions well. Additionally, we do not advise using a 60 mph highway to get to work during this testing phase. You might be fortunate the first time, but if not, keep in mind that disassembling and rebuilding your truck is enjoyable.
Considerations How long the links should be and where they should attach to the frame and axle are the two primary concerns when creating a four-link. This alone will decide how the axle pulls the car, whether the car’s back rises or squats when it accelerates, if the rear axle pivots and steers due to wheel articulation, and how the body rolls in corners and over obstacles. Depending on what the vehicle is supposed to do (go quickly, corner, crawl, or articulate), as well as how the driver wants the car to behave on various surfaces, the desired amount the vehicle performs each of these things varies. Similar to how there is no one perfect off-road vehicle, there is no one proper method to build a four-link, although it may be tweaked to accomplish some things better than others.
An all-purpose four-link is what most truck owners want, but it may not be the finest suspension for rockcrawling, desert jumping, and mud bogging.
The challenge of creating a four-link involves a lot of geometry, but there is also the issue of what will really fit on the vehicle you are making. Will the links be supported where you want them in the frame? Will the driveshafts, crossmembers, fuel tank, exhaust, and any other components fit with the links and provide correct articulation? Unless you are designing a truck or buggy around the suspension, prepare to make some concessions in order to have the finest configuration possible. We don’t blame you if the thought of preserving the leaf-spring suspension is beginning to appeal to you. Keep an eye out for next month when we start getting into the technical portion of the buildup if you’re up for the challenge.
You still have some homework to do until then. You’ll need to gather a pencil, graph paper, calculator, and tape measure. Go ahead and determine the height of the tires you want to run on your rig by measuring the wheelbase. Then, when the truck is on level ground, measure the width of the rear axle just inboard of the brake mounting plates and the height of the frame at various positions between the axles along the framerails. Next, measure the distance between your bellhousing’s top center bolt and the ground. Additionally, start looking into where you can purchase the supplies we’ve listed below. Just keep in mind that you should wait to tackle the four-link problem under your truck until you have finished reading the second installment of this narrative next month.
Managing axlewrap, improved departure angles, controlling axle path, and reducing the number of uncontrollable factors affecting axle movement to simply spring rate and shock valving are all advantages of a four-link suspension over a straightforward leaf-spring suspension. A four-link suspension can also allow for additional travel and articulation, which can increase traction, however we believe that having too much of either might lead to issues. The modern wheeler is likewise concerned about weight since too much weight depletes power. Even though a coil spring is lighter than a leaf spring, the weight savings are negligible when you also take into account the weight of the links, mounts, and other components.
Cost and upkeep are the key advantages of a leaf-spring suspension over a four-link. If you do it yourself, it will take more time and money to remove leaf springs and design, build, test, and rebuild your four-link suspension than it will to just install a reliable leaf suspension. Considering that shop charges can range from $25 to $75 per hour, a professionally constructed four-link will seriously dent your wallet. Additionally, several extremely impressive leaf-sprung suspensions with lots of travel and articulation have been demonstrated.
Material is a significant consideration for safety and strength. Depending on how low you install your lower links to the axle, they might run into trail impediments, therefore we advise using at least 1 3/4-inch DOM tubing with a 0.25-inch wall thickness. You should use even larger tubing, or better yet, sleeve the 1 3/4 x 0.25 with a slightly larger piece of tube, if your truck is a fullsize or particularly hefty, or if you intend to put your shocks on the lower arms like certain race trucks. Although rocks and other objects are less likely to strike the higher links, we still do not advise using anything less than 0.120 wall, 1 3/4-inch DOM tubing.
In This Article...
Are leaf springs replaced by a 4 link?
One of the biggest improvements you can make to your muscle car or truck with a leaf spring suspension is a 4-Link. Leaf springs are a tried-and-true suspension method that were created in the 1700s. Although leaf spring technology has advanced much since the “It has one big drawback: a leaf spring is expected to locate the axle and suspend the vehicle chassis, just like in the horse and buggy days. With the help of solid control arms and a separate spring, advanced suspension design has demonstrated that it is significantly better to isolate those two functions, which are also known as “links.
- Using the right jackstands, carefully support the vehicle. It’s risky to work on and underneath cars, so do it correctly.
- Remove the leaf springs and stock shocks. Leaf springs weigh a lot. Your rear axle is also. Make a plan for carefully removing these items. The day before the procedure, it is helpful to soak any hardware that might be seized or rusted with a solution like Liquid Wrench.
- Additionally, you might need to temporarily remove all or a portion of your exhaust system.
- the upper shock crossmember into place. You could decide to weld in the upper crossmember after grinding the paint off the frame rail.
- Use a set of jackstands to support the rear axle. To make installing the lower links easier, you should elevate the axle to around ride height.
- Install the lower links to the axle pads and front leaf spring mounts that were already on your automobile.
- The upper links should be put into the upper crossmember.
- Attach the weld on tabs to the upper links’ opposing ends. Double verify the centering of the rear axle. The placement of the lower link aids in axle alignment.
- To the upper axle, weld the tabs.
- Install the coilovers or shockwaves of your choice.
- Before your test drive, double check that all hardware is securely fastened.
- Your tailpipes might need to be modified, or you could have custom tailpipes built by a nearby muffler company.
- Go for a test drive after adjusting your CoilOvers or Shockwaves to the proper riding height.
thoughts on “4-Link Swap: A Smart Upgrade for Your Muscle Car or Truck
Says James Miskell
If not, do you have a kit that will work? Thank you. Can this kit be placed on a 1935 Plymouth sedan street rod with a Ford 8 rear end?
For drag racing, do you want a strong suspension?
It’s simple to get faster and more reliable elapsed times at the drag strip if you have a solid understanding of how to tune the rear suspension of a car. It’s simple to become lost in the wealth of information while examining how to adjust a suspension because there are so many different aspects and elements to take into account. Every racer needs to see this QA1 video, which provides a succinct overview of rear shock adjustment.
You must become familiar with the ideas of rebound and compression if you want to build a strong understanding of how to tune the rear shocks of your racecar. A firm setting will cause the shock to rebound more slowly, which will cause you to hit the tire harder when you need to contact the track hard with the tire. You can prevent the tire from “bouncing back up” and keep it firmly planted to the track surface by adjusting the shock’s compression setting. The amount of movement the tire will have depends on how stiff or soft the compression set is.
There are primarily two types of shocks with programmable compression and rebound settings. Single-adjustable shocks have a single knob that may be used to simultaneously modify the shock’s compression and rebound. These shocks aren’t the best for complete race cars because they are made for vehicles that get a lot of street driving. Double adjustable shocks include two knobs that let you modify the compression and rebound separately. High-horsepower race cars require these shocks to assist regulate how the tire interacts with the track.
When adjusting the shock, it’s essential to watch a slow-motion video. You can see in detail how the tire and the car are responding to the application of power in the slow-motion video. To determine how much separation is occurring and how the tire is responding to the shock setting, you should watch the car’s first movement. Based on how much separation you observe, the type of track and tire will also influence how you change the shock settings.
To learn more about modifying the compression and rebound of the shocks to tune the separation of the suspension, be sure to watch the complete video, which is being hosted by Steve Smith from QA1.
What distinguishes a 4 link from a radius arm?
Vehicles with solid axles typically utilize one of two suspension designs: the radius arm or the four-link. For a variety of reasons, different vehicles employ different settings. Older Land Rovers, which are noted for their superb off-roading, have a radius arm system instead of the 4 link setup used by Jeeps, which is supposedly better for off-road use. We’ll discuss the variations in the two suspension configurations in this succinct tutorial.
There must be a method for regulating the axle’s movement on a solid axle vehicle. Leaf springs serve as both a spring and a means of limiting how the axle moves. The leaf spring is fastened to the axle by u-bolts and is secured to the chassis at two locations, one of which contains a shackle to accommodate spring expansion and contraction. Unfortunately, coil springs cannot be used for this, which is why suspension links are required.
To help you understand how each design influences axle rotation, here is a brief demonstration.
By attaching the axle to the circular path the links will take, a coil spring system might control the vertical movement of the axle with just one set of links. There is only one issue: a single set of links won’t be able to prevent the axle from freely turning. You may keep the vertical control while also providing rotating control of the axle by adding a second pair of links. The axle spins differently as the suspension cycles depending on the length of one set of links or where it is mounted on the chassis.
By using a second mounting point on the axle per link, the same rotational control can be attained. By fixing the rotation to the course of the links, the two mounting points per link prevent the axle from rotating. The term “radius arm” refers to this kind of mechanism. A radius arm does away with the requirement for additional links while giving up the capacity to finely control the rotation of the axle.
Sadly, neither system is flawless, and they both have flaws. Strength and the capacity to regulate the axle in various scenarios are the main problems for both systems.
A radius arm setup has the drawback of effectively converting the axle housing into a torsion bar, which is somewhat akin to a sway bar. Even though there isn’t enough pressure to harm the housing, it is still present. Because the rotation of the axle is bound to the course of the link, radius arm systems similarly struggle to control the caster angle when the suspension cycles. Theoretically, this could increase bump steer, but unless you have a lot of travel, it usually won’t.
The simplicity and space efficiency of radius arm systems is one of their great features. The engine oil pan is frequently in the way, thus a long arm four-link system must be built to avoid hitting it. A radius arm arrangement prevents the chance of the link running into the engine oil pan by keeping the links away from the axle. Radius arm systems are also significantly less expensive than four-link systems since they require less research, development, and testing.
Depending on how the links are configured, four-link systems have the potential to bind the U-joints on the front driveshaft. The axle of the U-joints will grow as the suspension descends if zero caster change is tuned throughout the suspension cycle. Any solid axle system might theoretically experience death wobble, however the four-link configuration is more susceptible to it because there are more bushings that could wear down.
A four-link system’s capacity to triangulate the upper and lower arms is one of its extremely remarkable features. A Panhard bar is not required because the entire system is triangulated. Theoretically, the four-link system should have reduced binding, which can lead to increased articulation. It is possible to use just three links instead of four because the upper arms are essentially only used for rotational control.
In conclusion, there are a few significant differences to keep in mind. One link is used on either side of the axle in the radius arm system. Two mounting points on the axle side and one on the chassis are included on each link. Two links are used in the four-link system on either side of the axle, usually one at the top and one at the bottom. Both the axle and the chassis have a single attachment point for each link.