This is a Modified stock clip,...
This is a Modified stock clip, upper control arm mount. This is one of the cleanest and most efficient designs. It utilizes an adjustable mounting plate and aftermarket one-piece upper control arms. If every promoter would allow such changes, the competition would improve along with the handling of the cars.
This unknown factor can wreak havoc on our frontend geometry settings, and we might not even know how it has happened. For example, I could go to a lot of effort to measure my car, make the necessary changes, and then go racing and have a lot of success. Then, the inevitable happens and I get pushed into the wall, bending my right-front spindle. No problem, I think, and order a new 911/44-inch spindle. If the ball joint-taper holes in this spindle were drilled 11/48 inch deeper than the previous spindle, I could end up with an entirely different MC location.
I ran the calculations on a sample car, an outlaw Late Model. The dynamic MC location (its position in the middle of the turns) with the current design is 2.449 inches high and 0.137 inch right of the centerline of the car. I lowered the upper ball joint by 11/48 inch and raised the lower ball joint by 11/48 inch. The MC ended up at 2.230 inches high and 2.288 inches left of centerline. I would need to lower the Panhard bar by 11/44 inch on both sides to maintain a balanced setup after installing that spindle. It could be worse.
If my taper holes are drilled 11/44 inch deeper for the upper and lower ball joint shafts, the MC moves to 1.079 inches high and 18.764 inches left of centerline. That's no place for the MC. My car's handling will go bad and I won't even know why. I will usually blame it on a possible bent clip or whatever else comes to mind.
Here is a clever idea we came...
Here is a clever idea we came across. This team drilled and tapped the spindle and welded a nut on the top and bottom. They then used a large machine head bolt through a mono-ball to create the ideal arm angle for their Late Model. This arrangement allows a much wider range of adjustment, especially for raising the pivot point.
It would be a good idea to keep track of your spindle's taper hole depth after you have measured your car for the MC location. Keep these dimensions in a book, preferably your setup book. If you need to change spindles for some reason, you can check the depth of the new spindle ball joint hole depths and compare those with the "standard" you have established.
Chassis Mounting Point Heights
The heights of your control arm inner chassis mounting points can also be changed to affect the location of the moment center. We are often limited in how far we can go to move these points. To locate the MC in the correct spot, we might need to make changes to the inner mounts and the spindle.
Many chassis manufacturers now build their cars with adjustable mounting points so that we can move the upper and/or lower mounting points up and down to change the arm angles. This comes in handy if we need to make small changes to the MC location to adjust for different racetrack designs.
Many Modified cars as well...
Many Modified cars as well as some Late Model cars have a two-piece upper control arm. These have adjustable links for camber adjustment. The chassis mounting points have plenty of room for vertical adjustment. Please do not write in about the brake rotor being installed backwards. This team has already fixed that problem.
The track banking angle is directly correlated to the MC location. The lower the banking angle, the more toward the left we can position the MC. The range may be different for each type of car, but it is generally true that low banking requires a location more toward the left while high banking requires a location more toward the right.
The MC is usually designed for location as well as ideal camber change for the right-front wheel. We need to have zero camber change at the right-front wheel after the car dives and rolls in the turns. That is what the tire wants. The upper control arm angle largely dictates the camber change for the right-front wheel. Once we have established an upper angle at the right-front, then we need to keep that angle. Changes we make to move the MC right or left should be done by altering the upper-left arm angle. That's why we need adjustable upper mounting plates, especially on the left side.
Do not be afraid to cut off the upper mounting brackets and mount new ones that are of a correct height. It ends up being a few hours of work and months, or even years, worth of good results. Before you cut, make sure you know exactly where you need the new bracket to be placed both vertically and laterally so that the control arm shaft will clear the plate with the proper camber set.