This chart shows suggested...
This chart shows suggested dynamic MC locations for various types of asphalt circle track racecars. This information comes from research and feedback from teams.
5. The circle track stock car wants zero camber change, relative to the racing surface, in the right front wheel after the car dives and rolls through the turns. The right upper control arm angle mostly affects the RF camber change characteristics. When designing our MC location, we need to find the correct right upper control arm angle that will result in the least camber change after the car dives and rolls in the turns. This of course cannot be accomplished when running the BBSS setups where excessive dive will always cause excessive camber change.
The left front wheel will always lose plus or minus two degrees of camber regardless of the upper control arm angle and so we can incorporate changes to the left upper control arm angle to locate the MC range laterally once we have found the optimum angle for the right upper arm for ideal camber change.
6. The entire dynamic MC range for dirt and asphalt stock cars lies between 10 inches to the left or right of the centerline of the car. MCs that lie outside that range will be detrimental to the performance of the car. Shallow upper and excessive lower control arm angles (inside points lower than the ball joints) contribute to MC locations that are outside of the optimum range.
This is a chart showing suggested...
This is a chart showing suggested dynamic MC locations for different types of dirt racecars. This information is definitely in use today and comes as a result of a lot of research and feedback from dirt track teams.
Differences In Handling Caused By MCLocation
The primary reason why two seemingly identical cars will handle differently can often be traced to a front MC that is in a different location from car to car. It doesn't take much of a difference in arm lengths or chassis mounting point heights to cause a pair of cars to experience different handling characteristics.
It was just a few years ago that many professional stock car teams experimented with different lengths of upper control arms to tune the handling while holding to pre-selected spring packages and weight distribution numbers. What they were doing was moving the MC left and right in a trial and error way to try to find the ultimate handling balance for a particular racetrack.
Today we know better than to waste time tuning with control arm angles and lengths. We know that there is a combination of spring rates, moment centers, and weight distribution for each car at each racetrack that will make the car balanced and consistent. Knowing the role of the MCs and being willing to make changes so that our MCs are in the right position is one of the very first and most important steps we take to achieve the total handling package.
If you don't know where your MC is located, then you don't know the most important piece of information about your car. It's like not knowing what your timing is, or what tire pressures you are running, or gear ratio. Whether you are a team, a car builder, or engineer, make sure you understand the dynamics of the MC and know where it is located in your car. It's not a theory at this point in racing history, it's a fact, Jack.
Many racecar builders are...
Many racecar builders are incorporating slotted mounting holes in the chassis so the racer can tune their MC locations. This Lefthander upper chassis mount has a series of overlapping holes cut in it so that the bolt can be located at different heights to change the upper control arm angles. The lower control arm chassis mount is also slotted so that the lower control arm angles can be adjusted.
This lower control arm chassis...
This lower control arm chassis mount is slotted so that the lower control arm angles can be adjusted. Note that this one is all of the way up. This can compensate for the high amount of travel associated with the BBSS setups.
Note how these CRA Super Series...
Note how these CRA Super Series late models are rolling to the right as they go through a turn at Music City Motoplex. Photo by Kevin Thorne