Every modification in the custom car industry goes through a maturing process.
The technology is refined, heavily critiqued, and maybe if the modification is lucky, the public will approve and it gets mass produced (the really lucky ones get outsourced to China where it is cut and trimmed until it can be sold at the low-low discount price of $19.95 on late-night TV). In one way or another, this holds true for just about anything you can do to a vehicle. From a chop top, to a custom intake, to Lamborghini doors, there is a natural progression of things. You might even go so far as to call it survival of the fittest. If an intake manifold is produced that doesn't provide any performance gains, but it looks really nice, there is a good possibility that someone will keep tweaking with the design until it does produce horsepower. Certain modifications have been proven to work for so long that they become scripture. Take replacing your stock exhaust manifold(s) with headers for instance, that is a staple engine modification, no one would argue with you if you did it.
Air springs are not immune to that same cycle of things. I'm not exactly sure how far air springs go back, but I know that GM used them in the late '50s on passenger cars, but only for a short time and I can only guess at their reasons for not continuing the use of them. In the early '80s Randy Davidson manufactured one of the first air spring "kits" for the front of the Chevrolet 1/2-ton fullsize pickup. It was an easy truck to kit because the shock was already located on the outside of the A-arm, so it was a true bolt-in kit and NO it didn't lay frame. In 1992 Brian Jendro used airbags on a Toyota pickup for Jason Pang instead of using the then popular air shock, thus setting the stage for an industry revolution (in my opinion, it has developed into THE defining modification of the minitruck).
So for over 17 years minitruckers have been installing airbags in order to slam their vehicles lower than any other custom automotive clique. In fact, it has become such a mainstream modification that numerous companies have spawned out of the need for better quality or easier-to-install air suspension parts. Yet through all these years, it seems that there are some people who escaped the grip of evolutionary progression. How, after all these years of custom suspension advancement, can anyone still believe that you don't need to run a shock with airbags? And to make things worse, these same people (you know who you are) will tell others that their truck rides great without shocks. What I believe started this phenomenon of ignorance is that many people had their trucks static-dropped way too low without a notch or proper installation, making them nearly intolerable to drive. Then, once they installed 'bags and notched their frame, the truck rode wonderful in comparison. Many will say that using a Slam Specialties airbag and 'bags with stiffer spring rates work great in the front without shocks. But that's just it, a truck without shocks will ride great compared to a truck that is constantly banging the rearend against the frame and viewed in the same light, a broken finger feels great compared to a gunshot to the abdomen. So if you insist, you can continue to tell everyone how great your broken finger feels, but in the meantime let's ask the experts what they think about not running shocks.
After spending only ten minutes on the phone with the guys over at Slam Specialties it was obvious that they agreed wholeheartedly about this. Here's what they had to say:
Shock absorbers are an integral part of any suspension system. No matter what type of system you have, when you break down your suspension into its various parts it's easy to see the direct function of each component.
Springs: Whether leaf, coil, torsion bar, or air spring, their sole function is to lift or support the weight of the vehicle. Spring rates come into play in various guises but, ultimately and in its simplest form, the spring pushes the vehicle up to the desired height. Springs are not designed to absorb shock or provide damping in any way; which is why you'll see older vehicles, even with steel springs, "float" down the road.
Shocks: Shock absorbers are what actually control the movement of the vehicle's suspension under driving conditions. Properly set-up shocks allow for precise and predictable control over your vehicle; whether cruising, accelerating, braking, or cornering. In air suspension systems, shocks are also important for other reasons. Because air is compressible, and airsprings are essentially flexible pressure vessels, the spring rates vary. This variance is dependent on the height of the spring and the pressure inside. In most cases, this variability, along with the inability of the airspring to damp shock, causes the vehicle to bounce continuously after hitting an irregularity in the road. Bouncing can unload the tires and make handling difficult, if not dangerous. Shocks damp potential bouncing and allow the suspension to normalize very quickly keeping the contact patch of the tire pressed firmly against the road. This, in and of itself, allows the driver to remain in control.
Now, I know what you might be thinking-"I run stiffer 'bags and don't need shocks." While a 'bag with a stiffer spring rate inherently helps to damp shock to the suspension and reduces that bounce effect, they are no replacement for a good set of shock absorbers. Utilizing a properly set-up airspring and shock combination not only will give the safest ride but, in most cases, will also give the most comfortable and longest lasting. In any case, when setting up your suspension, always remember to work within the parameters of the components that you are using. Airsprings and shocks have the ability to work in a variety of situations. The keys to success when working with them are simple. Select the size and capacity of the components to fit the vehicle, make sure the angular travel of the airsprings are within manufacturer limitations, ensure that the air springs and shocks have adequate clearance throughout their range of movement and don't over-extend or bottom out either the 'bag or the shock.
Bottom Line: Shocks and air springs should ALWAYS be used together.
I've also been working with Steve Duck over at RCD for over two years about this same issue and they have developed a custom Bilstein shock that is designed specifically for air spring applications. I called upon Steve's input and here's what he had to say.
After spending the better part of 17 years in the aftermarket, hot rod and muscle car shock absorber industry, I was surprised to find out that a lot of vehicles were not running front shocks. At a show I came upon a beautiful '60s Chevy truck, 'bagged and sitting on the ground. After admiring it from a distance I took a closer look to see what kind of shocks it was running, but to my surprise, there weren't any shocks at all. How could this be, is there something inside these bags that damp the motion of the bag? I asked the owner how the truck rode, "great on a smooth road" was the answer. Well, in a perfect world, with only smooth roads, that would be ok I guess, but this is not a perfect world. How many of you have been driving down the road watching a wheel bounce off the pavement or felt the chatter of the car going around a corner as the suspension is upset from hitting a bump in the road? Bottom line is whether you have a vehicle with air, coil, or leaf springs a shock is necessary to control it.
Now, I have never been someone that tries to baffle people with engineering and numbers crap, so let's just start with the basics. A shock absorber's job is simple, it controls how fast the spring (or air spring in this case) compresses and rebounds. When hitting a bump in the road you want the suspension to compress absorbing the bump, the shock slows this compression motion down so that the tire can return to the ground quickly and get back to its job of holding the vehicle off the ground. How fast the shock slows the wheel can determine what you feel in the vehicle. If the shock has too much compression rate slowing the movement down too rapidly, it will translate into a harsh or jarring ride. On the other hand if it is has too little the vehicle will dip/dive and have less control when cornering. The opposite motion is rebound; this controls how fast the spring expands. Not enough rebound rate, feels as if you are getting pitched out of the seat and there will be a lot of upward body motion. Too much rebound rate and the vehicle will feel like the rear end is kicking when going over bumps. Often this is hard to differentiate between too much compression and rebound in the rear.
To get the best ride quality at RCD we set up our Bilstein shocks with valving that slows the compression movement, keeping the tire planted on the pavement. But the rebound rate can be 2-3 times more aggressive to control the expansion of the bag, this helps to settle the car quickly after hitting the bump. That said, just because you have a shock on the vehicle doesn't mean it is the correct shock, but having the wrong shock is in most cases better than no shocks at all.
I feel much better now after consulting the experts, knowing that it's not just me and that I'm not going crazy! Hopefully after reading this you can see how shocks not only offer a better ride in almost every case but can make the vehicle safer as well. If you're still not convinced, try shooting yourself in the stomach and see how that feels. For more information, contact the companies listed in the source box.