Does Your Suspension Bite?

As if suspension tuning weren’t already hard enough with the multitude of components that affect setup, manufacturers offer an optional tuning component called a third link, or torque absorber. While some racers might cringe at the thought of complicating the setup, others have embraced this component to help combat roll steer and boost forward bite.

“When you have a solid-rod upper third link, the very instant you accelerate exiting the corner all the energy is immediately transferred to the rear tires of the car,” says Glen Myers of Coleman Racing. “Depending on the track conditions and the chassis setup, this energy may be too much and too quick for the tires to control, and they begin to slip, causing a loose condition and loss of forward bite.”

Myers continues, “But with a torque absorber, the energy is stored in the spring or rubber bushings—depending on the style. This allows the rear tires to gradually, instead of abruptly, pick up the momentum from the drivetrain, producing more forward bite.”

Is a third-link torque absorber right for your team? And if so, what type should you choose? To find these answers and more, we talked to manufacturers and racers about the benefits derived from proper utilization and tuning of third-link torque absorbers.

What It Does

“The rear torque absorber is designed to do exactly what its name suggests,” Myers says. “It absorbs the torque that is transferred from the drivetrain to the rear axle, allowing the tires to get more bite on the track surface.”

As part of the rear suspension, the third-link torque absorber helps the rear axle accomplish two major functions: it gives the rear tires maximum traction and helps the front end turn. Mounted to the rearend and the chassis, essentially it is another component of the rear suspension racers can use to fine-tune handling. Of course, a lot of factors go into creating and managing those forces.

A third-link torque absorber will not correct, replace or even compensate for an improper chassis setup. Racers will still have to use traditional suspension techniques to find the right combinations. However, once you have a good setup, adding a third-link torque absorber and properly tuning it can improve the race car’s momentum through the turns. It’s not a secret, but it’s something that takes time and experience to tune properly.

“The torque absorber allows the rearend housing to wrap up and thus takes that instant shock away from the rear tires when a driver first jabs on the gas pedal,” says Wayne Lensing of Lefthander Chassis.

“If the rearend were solid, there would be nothing to absorb the throttle coming down,” says Super Late Model racer Rip Michels. “So the torque absorber acts like a damper for the power being applied. I don’t know if it’s really necessary, but it’s there for fine-tuning if we need it.”

The Choices

There are four basic choices in third-link torque absorbers: rod end, rubber pivot bushing, captured rubber bushing and spring link. The first three types feature solid rods in the center of the unit, while the latter has a spring link in the middle.

“Rod ends are common to asphalt racing and the most basic,” says Chas Howe of Howe Racing. “These are used most often on high-speed tracks where traction is of little concern. The rod ends keep the pinion angle consistent for fewer horsepower loss through driveline misalignment, as well as preventing tow change on rearends with a great deal of camber.”

While many race teams have started switching to the more elaborate, adjustable spring torque absorbers, Howe says rubber pivot bushing torque absorbers are still the company’s most popular-selling third link.

“The pivot bushing fits mounts for all three types of rearends and houses two high-durometer rubber chassis bushings to cushion torque in both acceleration and deceleration,” says Howe. “Plus, the steel housing of the pivot bushing assembly is legal in divisions that prohibit aluminum.”

Howe says that, thanks to the compliance of the rubber bushings, this type of torque absorber can be misaligned a great deal in any direction without binding. “Installed with a rod end at the front of the link, the pivot allows racers to run the third link at different angles laterally to affect handling,” he says. Myers further explains how the geometry of these bushings work.

“Once the car accelerates on the straightaway, and the tires grip the surface and the race car gains speed, the torque absorber begins to release the stored energy and the spring or rubber bushings return to their neutral position,” he says. “Most torque absorbers also have a dual-action rubber bushing that stores energy on deceleration. This bushing compresses when entering a corner and adds bite on corner exit.”

The final type of solid-rod torque absorbers is what Howe calls “captured rubber bushing third links.”

“They are basically an OEM A-frame bushing housed in a steel sleeve with a threaded stud attached,” he says. “The captured bushings work basically the same as the rubber in the pivot bushing, but with a stiffer rate and less travel.

“They are made with right- and left-hand threaded studs so they can be installed anywhere in place of a ¾-inch rod-end bearing,” Howe says. “However, the captured bushings allow for very little misalignment and can not be preloaded.”

Spring Link

The spring link torque absorber has become increasingly more popular with racers. But beware: the spring-loaded torque absorber can introduce unwanted handling problems for inexperienced suspension tuners. Racers who have never used a torque absorber should keep in mind the solid rod and bushing third links are much easier to tune and less expensive. However, if a racer wants to have ultra-fine tuning ability, adjustable spring torque absorbers could be the way to go.

“With the spring torque absorber we are able to change springs, or change the preload on the springs, so under acceleration it doesn’t shock the race car,” Michels says.

In addition to the spring, altering the mounting position of the torque absorber can have a dramatic effect on corner handling.

“The steeper you run the torque absorber, the more it will tend to tighten the car up under acceleration,” Michels says. “With the leverage geometry, it pushes down on the rearend and gives the race car more bite. The problem is you can get to a point where it has too much bite, because it unloads when you get off the gas.

“There’s a fine line there. The idea is to run as much bite as you can get coming out of the turn, without it hurting you coming into the corner.” Myers says Coleman’s spring-loaded torque absorbers meet the rules requirements for IMCA Modifieds.

“These rules require an all-steel construction, and the cars must run 5-inch diameter springs anywhere on the car,” Myers says. “Basically, this rule was intended to eliminate coilover springs and small spring torque absorbers.”

Coleman offers this style of torque absorber in two versions: a single spring with 5-inch diameter and 4.5-inches long and a dual-spring version that allows the driver to run two different rate springs on the same unit so it can work progressively.

“The softer spring will absorb the initial energy and gradually transfer that energy to the stiffer spring,” Myers explains. “This allows a longer length of time that the dual-spring torque absorber can absorb energy.”

There are a lot of options to choose from when it comes to third-link torque absorbers, but knowing how to tune them will generate the most success. “The position where the third link gets installed is more critical to performance than the type of third link or torque absorber you choose,” Howe says.

A third-link torque absorber is not the magic solution to suspension woes. But, along with a strong foundation in suspension tuning, third-link torque absorbers can be just the extra difference between a Top-10 and a Top-5 finish.