Shocks are both one of the most important aspects in a suspension and the most overlooked. Much attention is given to picking out just the right tubular control arms, and gearheads agonize over the decision between a three-link, four-link, panhard rod, Watt’s link, or whatever whizbang setup is the suspension du jour at the time. But when it comes time to pick out some shocks they often just fall back 10, punt, and hope for the best.
Part of this bad decision making stems from the buyer’s lack of understanding about what a key roll shocks and springs play in how their car rides and handles. In some cases manufacturers make it easier by packaging shocks with their suspension kits, but if not, it’s easy for someone to choose poorly rather than getting what’s needed to let the rest of their suspension operate at its full potential.
In a nutshell, shocks convert the kinetic energy of a spring’s movement into heat. With the energy converted to heat it can then be dissipated into the air through the body of the shock. Shocks and springs work together to maintain the maximum tire patch to the asphalt. If the road is flat and smooth this is pretty easy, but as corners and surface irregularities are added to the equation it becomes much trickier. If not for shock absorbers even the tiniest divot or bump in the road would send the car into an unending undulation down the road. This excessive bounce could be controlled by upping the stiffness of the spring, but that would result in a harsh and jarring ride that you would hate, but your dentist would love.
Fortunately, shocks do exist. While having the wrong shocks is better than having no shocks at all, the right ones can make a big difference in the performance of your Camaro and the quality of its ride. Nonetheless, in order to pick the right shocks it’s important to know a few basic concepts.
In shocks there are two basic settings: rebound and compression. Rebound damping helps control the part of the car’s sprung mass that is stored in a compressed spring and the rate determines how long it takes for the compressed spring to regain its static ride height. The farther you dial this up, the more the shock will resist the compressed spring’s effort to “rebound” to static height. Compression, also referred to as bump, is a damping function that controls the oscillation of the car’s unsprung weight. The higher the compression number, the more the spring will resist “compression” from its static ride height. Together these two forces work to give a car’s suspension its personality; either firm and sporty, or soft and cushy. Normally, compression is set less than damping, but like every rule, there are exceptions. One of these is when more compression is dialed into a particular corner to slow its downward movement, in essence giving the effect of a stiffer spring, however one should resist the urge to fix suspension issues through the shocks.
Also, spring rates play a role in this mix. They dictate how far a chassis pitches, rolls, or squats, while shock-rates determine how long it takes each of these movements to happen. But, that’s another story for another time.
Twin-tube Versus Mono-tube
For our purposes there are two basic types of shocks on the market today, twin-tube and mono-tube. Twin-tube shocks have been around for a long time. As the name states, the shocks are comprised of two chambers: an inner and a outer tube. The inner tube is where the piston moves through a main supply of oil. The outer chamber, or tube, contains an extra supply of oil and generally a low-pressure gas. This gas can be anything from regular air in the “el-cheapo” versions, to nitrogen in the nicer shocks. Whatever the gas, it’s typically pressurized at 100 to 150 psi. The downside is as the oil heats up, and it will under hard driving, it can mix with the gas and foam up causing shock-fade and a substantial dropin performance.
One key measurement that Steve Duck, of Race Car Dynamics (RCD), needs to know is how much room he has to work with. With the car at its ride height, a measurement is taken with the shock in the car from one eyelet to another. This data will help him determine what length shock will work best in a particular car.