We can see by diagraming the suspension (or just reading the part description) that MCA’s traction mod reduces anti-squat. Anti-squat geometry loads forces through the suspension linkages and bushings and ultimately to the chassis. The traction mod alters the characteristics of how these forces get loaded via modifying the trailing arm pickup. Let’s visualize this.
https://www.ft86club.com/forums/atta...1&d=1625862766
This diagram is simplified, but notice that the acceleration force transfers through the trailing arm (black line), into the chassis. Negative anti-squat tries to push the chassis down, lifting the rear wheel up and resulting in less traction. Positive anti-squat tries to lift the chassis, and there’s a corresponding downward force on the tire providing additional grip. Neutral anti-squat would result in no downward or lift forces, instead the acceleration force is just transferred forward into the chassis. Maximum acceleration is tuned using this geometry to determine how much of the engine’s power pushes the tires into the ground, and how much pushes the chassis forward. This is well documented in drag communities.
Next let’s look at the effects at equilibrium. When neither accelerating nor decelerating, the amount of force in the trailing arm is greatly reduced - until we hit a bump. The instant we hit that bump the tire momentarily gains a ton of traction. The wheel wants to move up and back. ‘Up’ should be handled by our spring/shock, so let’s focus on the ‘back’ right now. We can visualize this by reversing the acceleration force, which in turn reverses the other forces as well.
In the negative anti-squat scenario, we’re now lifting the chassis up, pushing the rear wheel down. This increases traction on the rear tire in a bumpy scenario (lots of mini deceleration forces). The amount of ‘up’ force our spring/shock deals with is also reduced since part is transmitted directly to the chassis.
In the positive anti-squat scenario, we’re now pulling the chassis down and lifting the rear wheel up. This jacking force means we have less traction at the rear tire in a bumpy scenario. This increases the ‘up’ force our spring/shock deals with and we are dependent on the resistance given by it for tire grip.
So that’s the theory as I understand it. There’s a lot of implications here, and keep in mind geometry is ever changing as the suspension works. In reality the MCA mod is a relatively mild change. Corner exit on rough surfaces is improved and it’s a little harder to kick the tail out when I want to. There’s probably a loss of performance from a dig and during corner exit on smooth surfaces, but I don’t see too many of those.
