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A chassis is the part of an automobile that the suspension mounts to. Most vehicles manufactured since the 1970s use a uni-body construction method. In this type of design, the chassis is not separate from the body, as it is in a vehicle that uses a separate frame. With uni-body vehicles, the chassis is attached to reinforced sheet metal mounting points designed into the body of the vehicle. Some vehicles, such as pick-up trucks and heavy-duty vehicles, continue to use a separate frame and the chassis, for these types of vehicles mounts directly to the frame.
For the most part, the chassis of a vehicle can be identified as any component that moves—other than the body—when the vehicle is bounced. Springs, struts and A-frames are all chassis components on a vehicle. Other well-known chassis pieces are control arms, sway bars and axle assemblies. Lesser-know chassis components such as drag links, tie rods and ball joints are very important to the handling of the vehicle. These lesser known components are often neglected when a vehicle undergoes servicing.
Most suspension pieces utilize a grease Zerk that allows the part to be serviced and lubricated. A few pumps from a grease gun will properly lubricate a suspension component and keep it in peak operational order. The proper time to perform suspension maintenance on most vehicles is at designated oil change intervals. Some newly-manufactured suspension components come without grease fittings. These components are self-contained and require replacement in the case of part failure since no preventative maintenance can be practiced without grease fittings.
When replacing a suspension component, vehicle owners should opt to use the most high-performance part available. Many vehicles are offered in different option levels or performance packages. The high-performance packages used much better suspension pieces for most of the system components. By replacing standard package parts with high-performance parts, the vehicle's ride and handling will be drastically improved.
It is often necessary to replace multiple components when upgrading any suspension item. Components such as sway bar bushings are much stiffer if purchased for a performance suspension package; however, they are also designed to fit a much larger diameter sway bar. In a situation such as this, upgrading to a stiffer sway arm bushing would require also upgrading the sway arm and the sway arm mounts as well as the mounting bolts. The result, however, will be a better-handling vehicle chassis when negotiating tight corners.