Slam It: 5 Basics of Airbag Suspensions
We recently posted a story about the basics of lowering trucks and thought it was fitting to go beyond by explaining how some trucks are able to sit flat on the ground. Many of the vehicles we’ve featured on this page are so low that some people think they don’t function. That is a bit true as they can’t really drive like that, but with the help of an adjustable suspension system, these vehicles can lay low when parked and raise up to move around.
Although adjusting the height of a vehicle was popularized with the introduction of hydraulics on lowriders, truck enthusiasts prefer airbags. In the lowrider scene, hydraulic suspensions are a quick way to make a car go up and down and even hop on command. Well, custom trucks are more about cruising low than getting airborne and airbags are a better way of getting there.
These systems use compressed air to inflate rubber "bags" that replace conventional springs, which have a fixed height. To drop a vehicle with this setup, the air is released from the system and the bag deflates to compress the suspension. Airbags also provide a smoother ride as long as they are used in combination with shock absorbers to prevent a vehicle from bouncing vigorously. They can be also be very reliable as long as they are mounted away from hot components like an exhaust and sharp objects that might puncture them.
Here is what a typical airbag looks like with a rubber bellows implemented for adjustability. Slam Specialties is one of the leading airbag providers and this example shows the solid upper and lower parts that are used for mounting locations. There is a port located up top so it can be plumbed for its supply of compressed air.
A variation to traditional airbags is the ShockWave produced by the folks at Ridetech. These are a great way to simplify installation as the airbag is integrated with a tuned shock. Though they are limited on how much height adjustment they provide versus regular airbags, ShockWaves hold up better for vehicles with high performance engines.
Airbags require compressed air in order to function and that means there are a few other parts that must be installed along with them. They need a steady supply of air from a reserve and most people use single or dual 5-gallon tanks to meet the demands of a system. Filling the tanks is done with compressors and it’s a good idea to incorporate water traps to prevent corrosion from condensation that may develop.
To regulate airflow to the bags, a set of valves are required, which will need to be managed by a pressure monitoring system or a controller like the Slam Specialties MC.2. These accessories are available from many distributors like AVS, Lowrider Depot and Switch Suspension.
The easiest way to swap in a set of airbags is to purchase or fabricate mounting equipment. If you have a coil front suspension, the springs can be removed to allow for an airbag to go in. The preferred method for a rear suspension is to add a multi-link system.
For older trucks that are a bit more difficult to modify, there are companies like Porterbuilt that offer complete front and rear kits. These products are easy enough for the DIY builder to install in a garage or driveway with a minimal number of tools. They are also better designed for tucking large wheels and providing modern drivability.
4. Full Chassis
A common problem for those working on classic trucks is rust and worn out pieces. Also, old frame rails were never designed to handle modern components and are usually tired. To really get the most out of a truck, a new chassis will get it there. Most of the offerings come with all modern components including rack and pinion steering for a better driving experience.
Though there are many options when ordering a full chassis, these systems are designed to bolt up to existing mounting points on specific bodies. Making the switch takes a bit of labor but there is very little guess work with a new chassis. Some of our recommended chassis builders include GSI Machine and Fabrication, the Roadster Shop and Scott’s Hotrods ‘n Customs.
5. Body Modifications
The latest trend in slammed trucks is to add air suspensions along with 20-inch plus wheel and tire combos. Since trucks were not originally intended to tuck large rolling stock, truck bodies usually have to be modified. Yes, the inner fenders can simply be cut open to make room for them, but open spaces will lead to road grime getting flung everywhere.
For those that have metal working skills, trailer fenders can be used to make new inner fenders to cover openings. There are also companies like Slosh Tubz, which make prefabricated pieces to fill the void. They can also be finished off to compliment the rest of the vehicle. Once installed, an airbagged vehicle can look good rolling and shock all when completely slammed on the ground.