The suspension system in a truck is key to the driver's comfort. Obviously the suspension system for the axles needs to be very good, but what a lot of new drivers forget is that the seats in the truck cab also have a suspension system. Two types of systems are available for truck seats for makes like UD: air and mechanical. Both of these work well in particular situations. You need to be aware of how your body reacts to constant sitting — low back pain is a problem among many truck drivers — as well as how the type of suspension would fit into the cab of the truck you're using.
Better Cushioning and Movement
Air suspension is a system in which the seat is protected from jostling and shocks by what are essentially bags of air (air bladders). You can refill the bladders using a button attachment on the seat. This type of suspension is more easily customised to the driver's needs and liking. While the driver may still feel movement, it will be less jarring, as the air acts as a buffer between the movement of the truck below and the driver's body on the seat. The result is better cushioning and less shock to the driver's lower back, spine and hips. Mechanical suspension, which is a more traditional spring-based system, can be more jarring, as the springs provide a direct, physical connection between the truck and the driver's body. More vibrations are transmitted to the driver, resulting in more stress on joints and muscles.
Cost Is a Factor
Air suspension systems are more expensive, so cost is a factor if you're buying your own rig. However, the added comfort of air suspension may allow you to drive for a longer time (within legal limits, of course), letting you get more deliveries done and earn more money. That suspension could pay for itself very quickly. If you're buying a totally new truck and can afford the extra cost, air suspension seats would be a good investment. If you have to get mechanical suspension due to cost issues, have the suspension inspected often to ensure it stays in good shape.
Replacing One With the Other
If the truck you own already has mechanical suspension and you want to add air suspension seats, you'll need to look at how the change in suspension configuration could affect your position in the cab. Some air suspension systems for seats are bigger than spring systems and can add height to the seat. You have to be sure that you can still reach the controls and see out the windows comfortably if that extra height is a concern.
Consider looking for for OEM parts from service dealers if you are looking to replace any parts, like a UD truck seat retailer.