You may be thinking, "what's the deal?" After all, we have a set of new, custom made leaf springs under our truck. Why would we need a set of Air Springs? Well the answer is quite simple. We're carrying a LOT of weight on this truck and we did not want leaf springs so stiff that it feels like the axles are bolted to the frame. So we contacted Air Lift and explained our predicament. They were happy to help and send out a set of their super duty air spring kit along with their Easy Street Dual Paddle Valve Gauge with which to control the pressure in each spring.
The 5700 super duty air spring kit comes with two 2-ply fabric reinforced air springs which are built like tires. They offer an additional load capacity of 5,000lbs. The air springs are molded with high-strength Zytel nylon. It is as strong as steel, but weighs less and is corrosion proof. The springs are mounted to the frame with the included brackets as well as brackets for mounting to the leaf spring pack.
To mount the air springs, we first had to find out how everything would line up considering we had the new Carrier leaf springs installed which have eight inches of lift in the arch. The first thing we noticed was that the ends of the u-bolts from Superlift would have to be shortened. So we broke out the DeWalt grinder and changed over to a cutting disc. We then chopped off the bolt ends so the Air Lift spring mount would set over the u-bolts and u-bolt plate. Then we put one of the springs together, hand tight, so we could determine where everything came together. It turns out the height of the springs meant that the frame brackets would not work in their designed mounting position. However, we found that if they are mounted upside down, that they work perfectly. In fact, in the inverted position, they almost perfectly match the contours of the factory frame rails. So we took the brackets to the local welding shop and had the outer lip of the bracket removed and a new piece welded on the other side for support. Once the brackets were modified, we were able to locate and drill the four holes per side so the brackets can be mounted to the frame. The big trick here is to have the truck jacked up so that the tires are just ready to leave the ground before installation. This way, the air springs will have the necessary resistance when the truck is setting under normal load. The supplied bolts were 3/8" but we decided to use 7/16" bolts to eliminate any play in the bolt holes.
Now that the holes were drilled, we had the brackets cleaned and then powder coated over at Spectrum Industrial Coatings. From here, it was just a matter of bolting everything in place and running the air lines. This is where it got fun. As mentioned earlier, Air Lift sent us their Easy Street Dual Paddle Valve Gauge assembly which is pre mounted in a panel meant to be mounted below the dash. We removed the gauge and paddles from the supplied panel. Next, we used the panel as a template to locate the new hole locations in the driver's side rear cargo compartment. We don't need to change the pressure on the fly, only when filling the RKO skid unit with water. So mounting them in the rear of the truck makes the most sense.
Using a 2" hole saw, we cut out the hole for the gauge. Then we used a drill type sanding wheel to enlarge the hole to fit the gauge. This was the easy part. Now we had to cut the rectangular holes for the paddle switches. With the hole locations marked out, we used a cutting disc on a dremel tool to make remove the metal. With a steady hand and a lot of patience, we had the holes cut. The edges of the metal were painted to prevent rust and after the paint dried, the gauges and switches were installed. All that remained was the routing of the air lines.
We decided to make the air line run as short as possible. So we started from the end of the Kilby air tank under the bed and ran the line up the the switches. From each switch then, we ran air lines to the individual air springs. Once again, the truck had to be raised. The instructions call for applying about five psi to the springs before setting the truck back down. Once in place, the springs can then be pressurized up the maximum of 100psi if necessary.
With the water tank empty, we'll be running at around 20psi. Loaded, we'll have the springs up around 80psi to keep the truck level and prevent side to side sway. We can't say enough about these springs and the extremely well engineered kit from Air Lift. We wholeheartedly recommend a set of Air Lift air springs for anyone with a vehicle hauling heavy loads. These air springs are the only way to travel.