Battle Magazine — March 1997

Shock absorbers are broadly divided into monotube and twin-tube designs. A monotube (single-tube) unit has the oil chamber, which generates damping force, and the gas chamber, which accommodates oil displaced by piston-rod movement, arranged in series and separated by a floating piston. A twin-tube unit has a double-wall construction: oil is sealed in the inner tube and gas in the outer tube. When the piston compresses, excess oil flows through the base valve at the bottom of the shock into the gas chamber. In a monotube, the gas chamber also resists compression.

Another design is the ram-type inverted shock. It is installed upside down, so the piston rod moves with the suspension. Because only the lighter rod moves instead of the heavier shock body, unsprung weight is reduced. On a strut suspension, lateral loads are normally supported by the piston rod; with an inverted design, the shock body moves and the shell carries those side loads.

The inverted design is stiffer than a piston rod and gives a firmer driving feel. Its main drawback is cost. Monotube and twin-tube units are similarly priced, but inverted units can be expensive. Because the piston rod carries less load, it can be thinner and the oil capacity larger, improving durability and extending replacement intervals. Balance these benefits against your budget. Adjustable-height shocks have become popular, but the ride-height mechanism is unrelated to the internal shock design. A height-adjustable shock is not automatically a better shock. If only one design exists for your car, there may be no choice, but otherwise evaluate the internal construction before buying.

Recently, hollow tubular stabilizers have also become available. Solid bars are heat-treated for strength, but the treatment may not reach the center evenly. Hollow bars can be heat-treated more uniformly, giving a crisper response during roll while also reducing weight. They cost more, but can be worthwhile. Pillow-ball upper mounts and suspension arms are other options. Compared with stock rubber bushings, they eliminate flex, improving steering response, traction, and braking stability. Pillow-ball upper mounts are the easiest upgrade and can make a noticeable difference: they improve steering response and transmit shock movement directly to the body for more linear handling. Ideally, use them front and rear, but if budget is limited, the front alone can still help.

A stabilizer limits body roll during cornering. In ordinary cars, it was developed to improve cornering while keeping springs soft for ride comfort. Proper use of stabilizers can substantially change handling. Bar stiffness is determined by its diameter; thicker means greater roll stiffness. Motorsport setups often proceed in increments of about 2 mm.