No discussion of shocks would be complete without including coilovers. Basically a coil spring wrapped around a shock absorber, coilovers offer the ultimate in suspension flexibility. Coilover shocks are available with fixed or adjustable damping, spring pre-load is adjustable, and optimizing the spring rate is a simple matter of swapping coils.
When selecting coilovers there are a number of factors to consider, not the least of which is the space available. That will dictate the length of the complete unit and the diameter of the springs. In most cases independent suspension systems need 2-1/2 to 3 inches of compression stroke while solid axles will require 4 inches or more (motion ratio will explain the reason for the difference). RideTech suggests that the shocks have approximately 60 percent of their travel available at ride height to handle the worst bumps.
Choosing the right spring for coilovers is critical and that's often where things go wrong. Coilover springs are rated by the number of pounds required to compress them 1 inch, and there are a number of steps to determine the spring rate required. Obviously vehicle weight has to be considered, however the goal is to find "corner" or wheel weight rather than total weight. RideTech recommends using race car–style individual wheel scales to accomplish this. Another option is to "axle weigh" each end of the car and divide the results by two.
With the wheel weights established, the unsprung weight, or the weight of the components not supported by the springs, like the wheels, brakes, spindles, rear axle housing, half the suspension links (because one end is attached to the chassis and the other to the wheel), and similar parts, are deducted from the wheel weight to determine the sprung weight.
The next consideration is motion ratio. That is the mechanical advantage independent suspension control arms have on the springs. Control arms act like a lever that not only makes the springs easier to compress, it also means they don't compress as far as the wheel travels. The more leverage the control arms have on the springs, the higher the spring rate needs to be.
Finally, is the angle of the spring or coilover in relation to the control arms (or the solid axle is so equipped)? Typically, this measurement will fall somewhere between 70 and 90 degrees.
Armed with all the pertinent numbers there is an easy way to determine the spring rate required: Plug them into the spring rate calculator found on RideTech's website (ridetech.com). While that procedure is not complicated, for anyone who has questions and would like to talk with a live person to get them answered, the tech team stands ready and is just a phone call away. And, if finding the necessary scales to do the job turns out to be an obstacle or if the array of shocks is confusing, RideTech has accumulated data on a variety of cars and trucks that makes it possible to make specific recommendations for almost every application.
Recently we had the opportunity to give a Model A Ford and a 1934 Chevy the shock treatments they needed. The Model A had parts house shocks of some sort and as a result of totally inappropriate damping when driving through curves and encountering rough pavement the suspension would chatter, which made the car feel as though it was skipping around. In addition, the suspension was extremely stiff over small bumps and things like expansion strips and seams in the pavement.
To improve its road manners we decided to give a set of RideTech Q-series shocks a try and as soon as the last one was put in place we went for a drive. The difference in the Model A was immediately noticeable—the disconcerting cornering behavior was gone and the ride was improved in all respects. While these shocks lacked a rebound adjustment, in this case it wasn't needed.
Our subject Chevy was equipped with independent suspension fore and aft with coilovers and antiroll bars—all the ingredients for a great ride and outstanding handling. Unfortunately, the springs must have been spec'd for a Mack truck judging by the retina-separating ride. The coupe was particularly brutal on SoCal's concrete ribbons, it was stiff and choppy as a result of spring rates that were too high and poorly calibrated compression and rebound damping.
After weighing all four corners of the coupe and plugging the info into the RideTech calculator we ordered four single-adjustable HQ series shocks with the recommended springs. With the proper springs and the rebound damping dialed in, to say the improvement was dramatic is an understatement. The new combination made the Chevy seem like an entirely new car.
When it comes down to measuring ride quality there are a number of sophisticated methods to evaluate shocks and coilovers. In competitive applications you can rely on lap times, skid pad numbers, or other measurable forms of performance. But with street-driven cars the results are far more subjective, so the feedback we rely on most comes from the seat of our pants. The methodology may not be high tech but it's accurate (no pun intended). When the suspension components are right, you'll feel it there first. We sure did.