Most people who own a heavy-duty pickup know what it's like to live a life of compromise. You purchased a three-quarter- or one-ton truck because you need the load-carrying capacity. But with the extreme GVWR comes a heavy-duty ride quality-or lack thereof-often accompanied by reduced vehicle control created by rear axle bounce. And did we mention axle wrap under acceleration and braking? That's just the way it is.

The engineering teams at Firestone Industrial Products and Sanluis Rassini felt they could find a solution with a new rear suspension system that tilted the compromise in favor of the end user. Firestone is known for its Ride-Rite air spring technology, which delivers additional load-carrying and load-leveling capability. Sanluis Rassini engineers and manufactures 96 percent of the leaf springs used in new vehicles in the U.S., bringing a slew of OEM-level design and testing tools to the joint program.

The two companies worked together to develop and patent the R4Tech hybrid air- and leaf-spring rear-suspension system. This new system gives customers improved ride quality and handling when the truck is loaded and unloaded. Additionally, it minimizes a counter-steering characteristic of a leaf-spring suspension that causes the rear axle to steer to the outside of a curve when there is a body line that compresses the suspension on one side and extends it on the other. The system also incorporates a kneeling feature that allows the rear of the truck to drop between 3 and 5 inches to facilitate loading the bed or connecting a trailer. Finally, the system keeps the rear of the truck at a ride height you can set, even as you add weight all the way up to the truck's factory-rated load-carrying capacity.

The R4Tech system replaces the massive factory spring pack with a leaf spring whose primary job is to locate the rear axle. A pair of Firestone air springs takes on the load-carrying responsibility. One significant advantage of loading the air springs is that the effective spring rate is variable, which means improved ride quality loaded and unloaded. As more weight is added, air pressure is increased and the spring rate goes up as needed, but it's still less than those of the original leaf springs. One of the key goals with the R4Tech system was to deliver a better ride quality than stock, regardless of the load in the truck.

A height-control adjust valve moderates the pressure in the air springs to keep the truck at the desired ride height. To control axle wrap, a J-link is added under the front section of the leaf spring. This maintains the distance between the axle and leading leaf spring mount, incorporating a rubber pad that contacts the main leaf under hard acceleration. The last component in the system is a pair of Ride-Rite LS tritube mono-flow shock absorbers. The valving in these shocks is automatically adjusted for greater control as weight is added to the truck.

Step 1:
The R4Tech system looks intimidating, but installation is easy and requires no drilling or special tools. All the brackets are powdercoated for a durable finish. The kit provides everything you need to complete the installation.

Step 2:
Start by giving the underside of the truck a bath to reduce dirt and road debris. We're using a vehicle lift, but the installation can also be managed with a jack and four heavy-duty jack stands. Make sure the truck is safely secured before removing the wheels. Support the axle on jack stands before removing the leaf spring.

Step 3:
In this GM 2500 application, the original four-leaf spring pack plus helper spring are replaced with a new leaf spring that has one full leaf and one half leaf. Sanluis Rassini is the maker of the original spring and the new one. The components in the R4Tech suspension system are manufactured to OEM standards.

Step 4:
Firestone's Brad Munchel is performing the installation on this truck. He recommends completing one side at a time to keep the rear axle located properly. The J-link front-mounting brackets use the leaf spring mount and the frame rail for location. Bolt the inner bracket to the top of the frame reusing an original bolt.

Step 5:
An outer bracket (arrow) bolts to the inner bracket and frame rail. Brad uses the leaf spring eye bolt for proper alignment. A third bracket clamps the front assembly to the inner frame rail and keeps the front mount from twisting.

Step 6:
The mounting brackets for the height-control adjust valve sandwich the frame rail where the original jounce bumper mounted. These brackets are designed to leave room for typical fifth-wheel mounts against the frame rails. New jounce bumpers are located inside the air springs.

Step 7:
The air spring and lower mount brackets bolt together. The air spring can then be bolted to the assembly.


Step 8:
The air spring assembly mounts atop the axle with U-bolts. The interlocking bracket that sits atop the factory leaf spring perch maintains the original spring pack height and provides a secure mount for the J-link bracket.

Step 9:
The air fitting on top of the air spring inserts into the upper air spring and height-control adjust valve bracket. There is also an alignment pin (arrow) on the air spring that must be inserted into the bracket: This keeps the spring properly located and precludes rotation.

Step 10:
Now the J-link can be installed. Start by inserting the front bolt in the bracket and link. Then the rear axle can be raised or lowered until the rear eye of the link and the bracket align. The link uses large-diameter rubber bushings to allow some movement for smooth, nonbinding operation.

Step 11:
An additional bracket installs with the rear link bolt, further tying the J-link mount into the leaf spring U-bolts. New U-bolts and lock nuts are provided with the R4Tech system. With all the brackets in place on one side, the bolts can be tightened. The leaf spring and J-link bolts are not torqued until after the truck is sitting on the ground at ride height.

Step 12:
The Firestone Ride-Rite LS shocks use air to adjust the internal valving. They are not air shocks, but use air pressure to provide variable adjustment. As the air pressure in the springs increases, the valving in the shocks is also increased for more load control.

Step 13:
With all the new rear-suspension components installed, Munchel turns his attention to the air-supply system. He threads the air fittings into the storage tank and bolts it to the mounting brackets. The kit uses U-bolts to attach the tank to the frame rail.

Step 14:
The air compressor mounts to the opposite frame rail, also using U-bolts to secure it. All air hoses included with the system use push connectors. Simply cut the hose to length and push the end of the hose into the connector.

Step 15:
The height-adjuster switch includes an air-release valve for the kneeling feature. When the toggle switch is flipped, the valve opens and lowers the rear of the truck 3-5 inches in a few seconds. The air tank holds enough air to allow the system to come back up to ride height with the ignition turned off.

Step 16:
There are a couple electrical connections to make underhood. A relay is included with the wiring harness. Battery power is tapped at the distribution block near the battery (shown), and a trigger wire connects to a keyed power source in the fuse box. The air filter (arrow) for the air compressor is also mounted here, keeping it high and dry.

Step 17:
The final steps are completed with the wheels replaced and the truck sitting on level ground. To set the desired ride height, lengthen or shorten the connecting rod from the spring mount to the ride-height switch. You can measure your truck before installation and set the height to that measurement, or you can level the rear of the truck to match the front. Torque the leaf spring and J-link

TAKING THE SUSPENSION FOR A TEST DRIVE

We tested the truck suspension before and after the R4Tech installation; we drove it both unloaded and with 1000 pounds of ballast secured in the Silverado HD's bed. You're familiar with the stock ride: bouncy, jarring, axle wrap under hard acceleration, and a lot of ABS activation as the tires bounce off the ground.

Driving the truck with R4Tech suspension installed and unloaded, we noted a couple differences. First, the freeway chop was greatly reduced. As the truck went over the concrete expansion gaps, that familiar bucking bronco feel was reduced to what you would feel in an average passenger car. The next place we found a significant improvement was on a washboard road. Previously, the back of the truck bounced so much that we felt we were merely aiming the truck down the road. With the R4Tech suspension, we had much greater control and it removed the worst ride qualities.

When we tossed 1000 pounds in the bed, the qualities of the R4Tech system really came to life. First, within seconds, the suspension leveled itself to the original ride height. In addition to looking good, it keeps weight on the front suspension for better control and retains the optimum front suspension height for alignment and handling. With the load, the new suspension actually made this heavy-duty truck a joy to drive and ride in. The ride was much less harsh, and the truck was very easy to handle. We especially noticed the improvement on the washboard road, over railroad tracks, and under heavy braking.

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