Setting the ride heights and...
Setting the ride heights and corner weights is the very foundation of every setup. Most of us don't have a steel surface plate to use for setting our ride heights and corner weights, but we can improvise using a fairly level floor and then spacing our scales so that the tires rest on a level plane.
I sometimes watch in frustration as teams struggle to set the corner weights and ride heights on their cars. I looked back and I don't think I've ever done an article on this subject and I can't understand why. The process is so basic to the setup of the car. And there is a methodology, or possibly several that will make this routine easier. Let's explore some ways to do this in an orderly and sensible way.
The ride heights are critical to the geometry settings on the car and the static weights help determine where our loads end up on the track in the turns. Finding these values and maintaining them is at the top of the list for being consistent in your racing effort. Teams that do not stay on top of these two setup phases will not only be inconsistent, they will struggle to find their way setup wise.
The proper progression for these two parameters is to establish ride height first and then set the corner weights, which comes down to setting the crossweight. There is a reason for this order. Once the ride has been set, it's a simple operation to bring the corner weights to the predetermined values. So let's study ride heights first.
Why Ride Height is Important
Your ride heights determine your arm angles up front, as well as the cambers, and, to a lesser degree-excuse the pun-the caster angles. Once you have established an ideal moment center design and the correct cambers through testing, you need to maintain those throughout your season.
Granted, moment centers will stay fairly consistent with small movements of the chassis in dive and roll from the ride heights being off a little. That is because all of the points move together. If you moved only one point, then the problems begin. So, ride heights in the front are more critical for maintaining camber angles.
There are legal issues too at the front. No, not as in the law, but in being legal in tech. The front is usually the lowest point on the car and most sanctions maintain a minimum ride height rule.
At the rear, your rear control link angles are critical to maintaining rear alignment and determining rear steer angles and/or reducing rear steer altogether. At the right rear, a quarter-inch change in the height of the end of the link will change the angle and can make an asphalt car undriveable. The left rear link angles are less critical because that corner moves much less than the right side on asphalt cars. On dirt cars, both rear corners can move quite a bit, so the link angles on both sides are important.
Establishing Ride Heights
Now that we understand the value in maintaining ride heights, just what heights do we want? First off, you must maintain the legal ride height to pass tech. Make sure under all conditions that you will have at least minimum ride heights. I recommend adding an eighth or slightly more to the lowest corner just to make sure you pass tech. Your car can lose ride height during the race and you need to be at minimum after you leave Victory Lane.
Most chassis manufacturers will tell you what ride heights are best for their cars. The car is built on a jig for a particular ride height layout. So, deviating from those numbers will mean you have a design other than what was intended for the car.
Some racers like to take matters into their own hands-and that's OK. Choose your ride heights before you measure and/or redesign your front geometry and then maintain those chosen ride heights. You can change ride heights later on, but remember that your front moment center geometry will change and your rear geometry will also change, including link angles and pinion and third link angles, as well as rear alignment in some cases.
The ring adjuster on a coilover...
The ring adjuster on a coilover shock is what is used to set ride height and corner weight distribution. Mark a place on the spring so you can measure the number of turns as you're setting ride height and weights.
This is a very good example...
This is a very good example of a stock class spring adjuster. We count the number of turns on the jack screw to determine how far we have raised or lowered that corner. Remember that a change to one corner of the car will affect the ride heights and corner weights on the other three corners as well.
Even in stock classes where...
Even in stock classes where jack screws are not allowed, we can use adjusters and still be within the spirit of the rules. Here we have found the correct spring height for our desired ride height and weights and then welded the ring so that it can't be adjusted. This makes it more of a spacer than an adjuster.