Rear Suspension Kits

What Are the Types of Rear Suspension?

There are several types of rear suspension systems. There are leaf spring, 3-link, and 4-link rear suspensions, along with independent rear suspension arrangements. A leaf spring rear suspension either uses a transverse leaf spring design or a pair of longitudinal leaf springs. This design uses either a single, or mono-leaf spring, or several leafs attached together, and bolted to the rear end. Leaf spring rear suspensions are prevalent in many street rods, muscle cars, and older trucks.

An improved rear suspension system came along with the invention of three- and four-link rear suspension designs. These designs used control arms top and bottom to attach the rear axle to the body or frame. With a 3-link design, you have two lower control arms and a single upper control arm. With a universal parallel 4-link you have two upper control arms paired with two lower control arms. With a 3-link and a universal parallel 4-link, a Panhard bar, or track bar is needed to center the rear axle. With a triangulated 4-link kit, the upper control arms are attached at an angle to the lowers. A triangulated 4-link kit keeps the rear end centered in the car without the need for a Panhard or track bar.

A ladder bar suspension is like that of a four-link suspension, except that most of the time, a ladder bar suspension uses one arm on each side, but they look like an upper and lower control arm in one. Ladder bar suspensions are popular in racing applications, but in most cases, true upper and lower control arms within a 4-link suspension offers more adjustability. Like ladder bar suspensions, some arrangements use a radius rod rear suspension, or a truck arm suspension. All of these are derivatives of a four-link suspension.

An independent rear suspension (IRS) uses a chassis/frame mounted center section that drives half shafts on each side to transmit power to the rear wheels. It also uses, in most cases, an upper and lower control arm on each side. An IRS offers better ride characteristics over that of a leaf spring or 3- and 4-link suspension since each wheel and tire are suspended independently from each other. Meaning, if one side hits a bump, the other wheel isn’t affected as much as would be in a typical non-IRS suspension. An IRS car will, more often times than not, handle better than the other suspension designs, as well. An IRS is better able to keep both rear tires on the pavement during hard cornering thanks to its independent suspension.

How Does a Rear Suspension Work?

A rear suspension has two jobs. The first is to absorb the bumps and the second is provide traction by controlling the rear end’s movement. A leaf spring suspension uses a plate and locating pin arrangement for an optimum pinion angle. That is another job of a rear end, to maintain proper pinion angle for a vibration-free ride. With a leaf spring vehicle, make sure the pin is properly located. Most of the time, the locating pins are on the bottom leaf since most often the leaf springs are on the bottom side of the rear end housing. Regardless, the mounting plate has a provision for the pin.

With a three- or four-link suspension the control arms dictate pinion angle. A rear suspension is designed to provide traction on acceleration, and the leaf springs or control arms are designed to keep the pinion angle within optimum specifications. Pinion angle doesn’t have a direct effect on traction, but a changing pinion angle does, so inferior control arm or leaf spring bushings will have an impact on traction. That is because if the control arms or leaf springs are allowing the rear end to move around, that will have an impact on pinion angle and traction.

How To Tell If Your Rear Suspension Is Bad?

There are a couple different ways a rear suspension manifests problem issues. If going over bumps you hear a loud banging noise, your springs or shocks could be worn out, and your rear axle is most likely bottoming out. Inspect your springs and shocks to confirm they are in good working order and replace anything that appears worn or damaged. If you have excess bouncing after going over bumps, your shocks are the most likely culprit.

For a leaf spring car, leaf spring rear suspension kits locate the rear axle using a spring perch bolted to the rear end housing. There’s a locating pin on the perch that fits into a provision on the housing that also uses U-bolts for attachment to the rear end, and either shackles or chassis mounts on each end fore and aft. With a leaf spring rear suspension, sometimes the locating pin can become damaged or worn, causing rear end alignment issues. You will know this issue when your steering wheel alignment differs from normal, and your car is dog tracking or “crabbing;” meaning your car is basically going sideways down the road due to a variance in your vehicle’s centerline versus its thrust line. Regardless of what suspension design you have in your car, pay close attention to the bushings, and make sure they’re in good shape. The bushings alone can make a big difference in your driving experience.

Can Rear Suspension Affect Steering?

Yes it can. A leaf spring rear suspension, if not properly attached, can affect steering alignment, and cause dog tracking as well. Also, bad rear suspension bushings can affect your steering too. If rear suspension bushings are defective or worn out, on throttle/off throttle acceleration and deceleration can affect steering. When accelerating, the rear end will shift to one side, then when you come off the throttle the rear end shifts back. This is something you can definitely feel in the car, and can be attributed to worn out bushings. If you have a 3-link or a triangulated 4-link kit rear suspension, the housing bushings or upper control arm bushings, if applicable could be worn out. If your vehicle makes directional changes during on throttle/off throttle acceleration and deceleration, and your tires are properly inflated, your next check needs to be the rear end bushings.

How Do I Stiffen My Rear Suspension?

The easiest way to stiffen your vehicle’s rear suspension is by adding performance-oriented coil springs, heavy-duty leaf springs, and/or stiff, polyurethane or solid bushings. For most, the simple addition of performance shocks will stiffen the rear suspension, but for even more stiffening, performance springs, and replacing rubber bushings with those made of either Polyurethane or Delrin material will also help.

If you’re wanting to stiffen or tighten up your vehicle’s rear end movement, perhaps from a pinion angle standpoint, traction bars for a leaf spring arrangement, and solid control arm bushings along with a Panhard bar or torque arm suspension will help the typical 3-link and 4-link rear suspension kits. Usually when a person wants to stiffen their rear suspension, it’s to improve handling. Our G-Comp suspension kits are designed to stiffen the rear suspension, and improve handling at the same time. If you have an early hot rod or street machine, any number of our four-link rear suspension kits will greatly improve performance and handling.

How To Improve Rear Suspension?

The easiest way to improve your vehicle’s rear suspension is by bringing it into the 21st century. Old technology is exactly that, old. Not everything new is great, but when it comes to older hot rods and trucks, technology has provided new ideas to help improve rear suspension compliance. Whether it’s through new ideas in componentry or new ideas on geometry and how parts act when paired together, updating your vehicle’s rear suspension with new bushings, new control arms, a new triangulated 4-link kit, or ladder bar suspension can really ratchet up the driving experience.