Suspension Tuning Guide - Tweaking And Tuning For Twisties

Our Goat
With our LS2-powered GTO injected with a healthy dose of performance, we were eager to test it around Gainesville Raceway's circuit. Before we even touch the car, however, we need to know what each adjustment does so we will have a better idea how to tune.

Shock Tuning
The KW V3 system we installed on our '05 GTO came with independent two-way damping adjustability for compression (aka bump) and rebound. Looking at these shocks on paper, there is an overwhelming amount of possibilities for suspension tuning, with 19 settings for rebound on the top of the shock and 14 settings for compression on the bottom. This leaves us with 266 possible combinations for each shock-wow!

Rebound-Shock Extending
According to KW Automotive, generally a soft rebound adjustment provides a comfortable ride at low vehicle speeds, but less stability at higher speeds, especially the front-end. The vehicle will tend to float if the rebound is set too soft. A hard rebound adjustment offers more stability at higher speeds, but it could reduce vehicle grip and the car will tend to skip across road imperfections, reducing traction. Adjustments to rebound are made on the top of the shock.

Compression/Bump-Shock Compressing
Bump and compression are interchangeable terms, but most of us are familiar with compression, therefore we will also call it compression throughout this article. According to KW, compression damping plays a larger roll in controlling dive and turn-in, since hydraulic resistance of the damper reacts faster than the springs in a dynamic situation. This helps a tire dig-in when you turn, brake or accelerate, and supports the chassis so that it doesn't move excessively. However, too much low-speed compression can reduce grip as it overpowers the tires. Having adjustable compression damping is a great tool if you have to set up for different tire compounds. Setting of the compression is done from the bottom of the shock case on KW shocks.

Shock Settings
Though, KW offered us a good starting point via its out-of-the-box settings, every car will like different shock tuning. When changing settings, you should first zero the rebound and compression by turning them full clockwise while counting the clicks. This will "stiffen" them as much as possible and reseat the damping adjustment check valve to ensure consistent damping forces between the two sides. Then dial back the setting, counting the clicks to your next desired position, and keep a log to document the car's behavior. Adjust by one or two clicks to rebound or compression at a time. This is the most accurate way to make changes and document them.

Our '05 GTO has adjustable Hotchkis sway bars, and Jay Chen of KW suggested that we back them down to their lowest settings and tune the shocks independently of the sway bars. If they were left at the previous, stiffer settings, the car could push through corners. We set the front at 1 of 3 and the rear at 2 of 4. We left them at these throughout the testing because the car exhibited near perfect bodyroll and didn't hit the tires too hard or soft.