Tires and suspension bushing also greatly influence ride quality. Most OEM suspensions use large soft rubber bushings and tall tires to enhance ride quality and noise transmission. Some classic truckers like to use polyurethane bushings and low profile tires. It is especially tough to get a decent ride quality with such a combination.
CT:Other than being able to raise and lower your vehicle, how do air bags affect ride quality?
BV: This is exactly where the air spring suspension shines! Assuming that a feasible air spring is selected for the suspension, it can be tuned to the parameters of the vehicle and the customer by changing air pressure while on the road. Likewise, an adjustable shock can be tuned to individual taste. In theory it is possible to make a vehicle ride as good with traditional springs as with an air suspension. This would require the aforementioned spring and shock testing. All of this tuning would need to be repeated when there are significant changes made to the fuel load, passenger load, or road surface. With an air suspension and an adjustable shock, these changes can be made in a fraction of the time. It is analogous to tuning a carburetor or tuning EFI. The EFI is much more versatile.
The analogy to EFI is relevant in other ways, too. As with anything adjustable, it is possible to adjust yourself into a terrible ride quality. The mistake most people make is too low of air pressure or too soft a shock [or shock adjustment]. This will allow the airspring to collapse too rapidly over a bump. Since an airspring is very progressive (spring rate rises in compression) it feels too firm. Many times adding air, or using a firmer shock will actually result in a better ride quality.
Symptoms of low air pressure are bouncy ride on rolling bumps and bottoming on potholes. The best way to start tuning an air suspension is to inflate the airsprings to their design height. Any competent air suspension manufacturer will be able to tell you this dimension. This is where the airspring is designed to work the best.The best ride quality should occur within a 1/2 inch of that dimension, regardless of the air pressure. After that is accomplished, start playing with the shock adjustment.
CT: What is the ideal air pressure for bags?
BV: That's a question with many answers! Run whatever air pressure it takes to get the air spring to its design height. A '32 Ford may take 45psi; a '57 Chevy may take 75-psi; an F-100 may take 60 psi. Keep in mind that the weight of the vehicle is only one factor in determining how much air pressure is required. A much more important influence is the geometry of the suspension. The relationship of the load point versus the pivot point versus the position of the air spring will be a huge factor in determining the selection of the air spring as well as what air pressure is required. If you are building your air ride suspension from scratch, these are just some of the factors that have to be considered. While you are at it, you must account for ground clearance, driveline angles, and ball joint travel limits. If you have purchased a pre-designed system from a manufacturer, these issues have been addressed [or should have been].
CT: How difficult is it to build a custom suspension from scratch?
BV:No Problem! Building a successful air ride suspension is no different than any traditional suspension. It is actually easier.
In a leaf, coil, or torsion suspension you have to have some educated guesswork as to where the vehicle ride height will end up and how the ride quality will be. Everyone has their favorite recipe for using coil springs out of a Malibu with one coil cut off, or leaves from an S-10 with one leaf removed. These will all work to a certain extent, but lets look at why they work and what would make them not work as well.