Firestone R4Tech Air-Over-Leaf Rear Suspension

Story & Photos by Trent Riddle
Super Smooth Hybrid Truck Suspension
The R4Tech kit doesn’t change the overall look of the truck. From a distance it looks stock and sweet as ever. However, the truck owner tells us that the ride, both unloaded and towing his trailer, is much better and handling well too. In his own words, “The kit worked flawlessly all weekend. Rode well, and handled well.”
Do you have a love/hate relationship with your 3/4 or 1-ton truck? You love the way it looks, the ease with which it tows your trailer and toys, its ability to haul a bed full of whatever heavy stuff you need to transport. However, the way your truck rides when unloaded and empty spikes the hate meter. The bouncy ride and harsh bumps when empty are something you can do without. Sure you could trade it in for a 1/2-ton rig, but then you lose a lot of capacity that you wanted when you bought your rig.
Now there is a solution and it fits both stock, and lifted late model Chevy/GMC, Dodge and Ford 3/4 or 1-ton trucks. This solution is the R4Tech suspension system from Firestone Industrial Products. This is the group that offers the well-known and reliable Ride-Rite and Coil-Rite air helper springs. However, the R4Tech suspension takes light trucks, 3/4 and 1-tons, to a new level.
The R4Tech setup is a hybrid air-over-leaf design that provides the ride quality of a big rig’s air ride suspension with the ease of installation found in standard leaf springs with Ride-Rite systems. With an R4Tech rear suspension installed, you can expect a better ride, both loaded and empty. This results in reduced wear and tear on both the rig, the cargo and the passengers by reducing noise and vibration and bounce. Another feature is the automatic load height adjustment. As you add cargo and/or trailer tongue weight, the R4Tech system will automatically adjust the suspension height back to unloaded ride height. This is not infinite, as the system is designed to work with your truck’s stock load capacity. In other words, you’ll still have the 3/4 or 1-ton capacity of the original truck (Air bags do not make your light truck a super 2-ton hauler.).
Besides a better ride, the R4Tech system also adds improved handling both loaded and unloaded. This is not to say that your truck will become a canyon racer. The air-over-spring rear suspension provides a wider optimum behavior window than a thick and stiff spring pack. This is under both loaded and unloaded conditions. There is a lot of math to explain this, and we won’t get into it right now, but you can find simple to understand information at Click on “Technology” and then click on “Advantages of a Level Vehicle.”
Firestone industrial is the point company on the R4Tech product line, but they have partnered with two other industry giants to bring this ultimate air-over-leaf rear suspension to market. These companies are Rancho Suspension and SANLUIS Rassini. Rancho is supplying custom valved RS9000 shocks and SANLUIS Rassini is the preeminent supplier of springs to the North American light truck industry. You’re getting the best from the best when you install an R4Tech system.
So you want to know how easy the R4Tech kit is to install? The answer is, very easy. The kits are designed to be a no-drill installation. This means that everything is bolt-on for the trucks they are designed to fit. Of course, this doesn’t take into account the addition of any aftermarket parts or prior modifications you may have made. But honestly, the same can be said for anything you want to install on a modified truck. The air plumbing uses simple push-on connectors and the compressor comes with a pre-wired harness that needs only four connections. Virtually everything needed comes in the kit. For our installation, only the two stock spring shackle bolts where reused. Simple hand tools, a 1/2-inch air impact, and other standard equipment required to swap the rear springs are all that are needed to install an R4Tech system.
1. The first part of the installation is to remove the stock rear springs. These massive bundles of steel are heavy. In fact, installing an R4Tech setup can shave over 140 pounds off some 1-ton truck applications. 2. As with all the parts in the kit the frame brackets go in with no drilling. The lip on the inside frame brackets grip the frame as the bolts are tightened. The front spring hanger brackets locate off of the stock spring hanger brackets and bolt to the inside frame brackets. These brackets are the forward mounting point for both the R4Tech replacement spring and the J-link (shorter secondary spring).
3. The lower spring mount is bolted to the lower air spring bracket with a single bolt. This assembly is held in place by the U-bolts and spring so this bolt is just to keep everything in place for assembly. The difference between a kit for stock or lifted applications is the height of the lower spring mount and the length of the air bag. Other than this, everything is the same. This means that if you install the kit on your stock truck, you can order a few parts and lift the rear. Then all you have to do is find a front kit only. Some manufacturers will allow kits to be sold as components and of course 4 Wheel Parts can help with this. 4. The upper air spring bracket is installed in approximately the same place as the rear bump stop for this Ford kit. Again, it is a simple bolt on.
5. The air springs are mounted to the lower spring mount and air spring bracket assembly with a single bolt. The entire assembly is then installed over the axle housing with the included U-bolts. Note: The Air Springs are rated at 100 psi continuous operating pressure, with large safety factor for intermittent pressure spikes from pot holes and such on the road. 6. First the main replacement spring is installed and the U-bolts are torqued down. Next the secondary spring (called the lower control link or J-spring) is installed.
7. An air compressor is standard for the R4Tech system. The standard unit is a 30-percent duty cycle compressor and is suitable for 90-percent of applications. In the extreme case where a commercial user is constantly raising and lowering the rear of the truck, a longer duty cycle unit is an optional upgrade. 8. Here’s the main part of the R4Tech suspension upgrade completed. The R4Tech kit comes with a thinner and lighter replacement main spring and a secondary forward spring. This secondary spring is called the lower control link or J-spring. The J-spring controls axle wrap and brake hop. This extra spring results in what is essentially a 4-bar rear suspension. The J-spring also contains a bump stop that contacts the main spring under extreme load or travel from uneven roads and trails and pot holes.
9. The Kit comes with a 3-gallon reserve air tank. This tank holds enough air to raise and lower the rear of the truck two cycles before activating the air compressor. The tank also serves as a buffer when loading the truck so that activation of the self-leveling system will not always result In compressor activation. 10. An air intake filter is provided to ensure clean air for the compressor. This filter should be mounted high under the hood to be sure that water is also kept out of the air intake.
11. In the upper right of this photo you can see the “height control valve.” This is essentially the brains of the load leveling system. This is a completely mechanical valve that controls the ride height of the truck. When loaded, the valve moves down and the compressor/tank adds air to the air springs. Then you remove the load, the arm moves up and the valve dumps air from the air springs, without losing air from the storage tank. This load leveling mechanical switch must move 3-degrees off center and stay off center for 30 seconds to activate. This prevents air transfer from minor suspension travel due to road surface conditions, pot holes etc. 12. Custom Rancho Shock RS9000 shocks with “load adaptive valving” are part of the R4Tech system. These shocks are plumbed into the air circuit for the air springs. As pressure in the air springs raise and lower for load conditions, the valving in the shocks adjusts too. This operation is automatic and seamless.
13. The R4Tech, and all Firestone Air Spring kits, come with the option to fill the air springs manually. This is great for the initial fill and as a backup, should you have a compressor issue in the far future. These manual valves are independent side to side. Here you see the lower plate mounting holes have been used to locate the air fill valves. 14. The manual air dump valve, standard in the kit can be used to raise and lower the back of the truck. This is useful when connecting to trailers or loading large items into the bed. For our application, a 2008 Ford F350, the height difference is a full five inches. This varies with the application, depending on axle centerline to rear of truck length.
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