Sanluis Rassini is the manufacturer who makes all of the leaf and coil spring suspension for the automakers in North and South America. They engineer their products to an exact science with software that allows them to calculate and understand the limits and characteristics of how metals will react under loads and stresses that are put on them from any number of conditions that a vehicle will encounter. This allows them to manufacture a vehicle's springs with perfect math and geometry. However, in an effort to hit the bottom line that allows the automakers to be competitive in their product offering to the public, OEMs request a simple and cost effective solution that meets the requirement to handle the payload capacity they are selling. The compromise on a heavy-duty diesel pickup suspension is the traditional leaf spring pack that comes with the truck. The leaf springs that come from the factory are designed to carry the maximum GVWR that the manufacturer gives the truck. This is why your truck's ride improves when it has a 1000-pound load in the bed. This is also why your truck has a stiff ride when it's empty. Sanluis Rassini designed the R4Tech kit to provide an aftermarket suspension solution that would spoil us with regard to the way our trucks ride. They've shown us that we really can have the best of both worlds-our one-ton truck can ride smoothly and handle like a half-ton truck when it's empty. And when we want to haul something heavy, we just throw it in the bed or hook it up to the hitch and watch as the truck automatically levels itself to carry the load. Even better, when we want to hook up to a trailer, we just throw a switch on the dash and as if we're cruisin' with our homies in East L.A., the back of the truck drops down so we can back under the trailer without cranking the trailer jack. Once we're under, throw the switch again and the truck rises back up, bringing our trailer with it.
How It Works
The large, heavy factory leaf pack is removed and replaced by this light-weight spring. This light spring provides a lot of flex and because of the reduced number of leaves, the friction between them is reduced, which provides smooth travel throughout its range of motion.
The lower control spring connects the front of the axle to the frame, which reduces axle wrap under acceleration and axle hop under heavy braking.
The load of the truck is carried on large Firestone airbags. The system is connected to an onboard air tank that remains pressurized to allow the airbags to self-level the truck as needed.
Leveling valves that tie to each side of the axle sense when the truck is high or low and adds or releases air to/from the airbag as necessary.
Adaptive shocks are tied to the airbags with an air line so the shock stiffness automatically adjusts to match the amount of air that's in the airbag.
The R4Tech kit utilizes the factory leaf spring perches for the main spring, but also uses this forward bracket to support the lower control spring. The bracket clamps over the frame and bolts to the factory spring perch.
The Firestone airbags mount between the axle and to the bump-stop brackets on the frame of the truck. This photo also shows the adaptive shock absorber and the small black air line that is used to provide proportionate amounts of shock dampening, depending on vehicle load.
The air compressor mounts to the frame rail under the truck. All of the air lines are slip-fit connections that make plumbing the truck for air a piece of cake.
We would like to have mounted the air tank under the truck on the frame rail, as it was intended, but we didn't have the space under the truck because the combination of following items got in the way: AMP Research PowerStep motor, 5-inch exhaust, the spare tire, and plans for a 56-gallon under-bed fuel tank. So we decided to mount the tank under the Roll-N-Lock cover's enclosure at the front of the bed.
After installing the R4Tech kit, the ride of the truck when empty and unloaded has dramatically improved over the stock suspension. You'll notice that in your three-quarter-ton or one-ton truck, most of the harshness of the ride comes from the rear axle. The front axle always has the weight of the engine on it to keep springs loaded with the weight they were intended to carry. Also, the amount of weight on the front axle of a truck doesn't fluctuate with different loads as much as the rear axle. If you hook up a 15,000-pound trailer to a gooseneck ball in your bed, you'll probably see the front axle gain about 200 to 400 pounds, while at the same time you'll see the rear axle gain around 2,500 pounds, depending on the tongue weight of the trailer.
When the truck is loaded with a heavy trailer, the airbags inflate effortlessly to level the truck. The R4Tech suspension doesn't allow the truck to squat like it did before at any time and the ride when loaded is much better than it was with the stock suspension. Load control is great too. If one side of the truck is loaded heavier than the other, the airbag on the heavy side will automatically level the truck on that side. When using a truck with this kit installed, it's important to note that there won't be any signs of overloading if the truck's weight capacity is exceeded. You would probably see the tires fail or brakes overheat before the truck began to sag, so it's important to be aware of how much weight you're carrying or towing.
The leveling system is always on the lookout for the correct ride height. We've noticed that even with a few people in the back seat of the truck, we can hear the air bags relax by releasing air after the passengers exit the vehicle.
The only negative criticism we have about this kit is that the installation instructions could be better. There were several instances where we found ourselves scratching our heads, trying to figure out the placement of a bracket or two. But now that we've completed the install, it's really not so bad. We think we could install another kit within eight hours now that we know where everything goes. We also wish that the air compressor was a little more quiet when it's running. The compressor keeps the tank charged with air up to 150 psi before the pressure switch shuts off. It won't kick on again until the tank pressure drops down to 100 psi. So, the compressor doesn't usually run more than a couple times a day, but when it does you're passengers will ask, "What's that?" But as we mentioned earlier, this suspension kit and this truck have spoiled us, so take our griping for what it's worth.
We highly recommend the R4Tech kit for anybody with a three-quarter-ton or one-ton truck.