A lot of the art of shock adjustment is seemingly pretty basic, but as a Motorsports Engineer and someone who is hired frequently to sort out ill-handling cars, I have found the #1 cause of handling problems to be miss adjusted shocks! Even well-funded pro teams with engineers often get shock adjustment wrong or screw themselves into a corner where the shocks don’t work and the car gets slower and slower. The major things I see people mess up on are the most simple basics, and the more knobs a shock has, the more screwed up they get things. Because of this, I am going to start with the most simple stuff first on the most basic performance shock, the single adjustable Coilover. I would like to thank KW suspension and ST Suspension for loaning me the shocks out of their trade show booth and giving me some supporting graphics that look better than my crude drawings would. If you are into this sort of stuff, it would not hurt to also read my Ultimate Suspension Set-Up Guide stories.
This video goes right along with this article!
The #1 problem I see with most people is that they set the ride height too low. The manufactures recommended ride height is the best place to start but everyone is always tempted to go lower because that looks cooler or something. Several bad things can happen. You can run out of travel and dwell on the bump stops during steady-state cornering, this causes bouncing and a loss of mechanical grip. If one end of the car bottoms out during cornering and the other doesn’t, the wheel rate of that end of the suspension gets nearly infinitely stiff which can cause sudden under or oversteer. Going too low can affect your suspension geometry to where things like, bump steer, too fast of a camber curve, weird anti-effects, and roll center issues like jacking arise. Finally, if you set your ride height too low, especially with the type of coil overs that have independently adjustable spring preload and ride height, you can put your suspension into places where it was not designed to go, leading to parts binding and even breaking, both severely affecting your handling!
One quick tip to ascertain if your car is too low is to put a small zip tie on the shaft. Now drive around quickly but don’t go out of your way to hit FIA curbing or other big bumps, you mostly want to see if the suspension is bottoming just under the loads caused by cornering, braking, and acceleration. After you can do this, you can see where the zip tie ended up. If the zip tie still has a bit of travel on the shock shaft, you are ok, if it is shoved way up into the bump stop, you should either raise the car or get stiffer springs, maybe both!
Many coil overs have adjustable camber plates. This means you should align your car after you install them. What specs to use is a whole different subject but you would be amazed about how many people don’t do this! You should also check your alignment every time you change your ride height as well. While on the subject of this part of your chassis setup, you should always be cognizant of your corner weights, this could also be the subject of an entire article on its own but I will skim over it here. If you have a race car, you should corner weight it and attempt to get your wheel weights as even as possible with equal right and left cross weights. For street cars, getting the same ride height from side to side usually gets the corner weight close enough. This all might seem obvious but many times I see cars done by people who are not even aware of these things.