rallycross cars on brake they change the differential strenght? if so, why?
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Yes, rallycross cars often change the differential settings on braking, and the primary reason is to optimize car behavior and handling under extreme conditions. Differential settings in rallycross are highly adjustable to suit the unique demands of various surfaces and driving situations.

### **Why Differential Settings Change on Braking**
Differential adjustments during braking are primarily aimed at achieving better stability and control. Here's how it works:

1. **Improved Stability:**
   - During braking, especially hard braking before corners, the weight shifts to the front of the car, reducing traction on the rear wheels. A looser differential (less locking) on braking can help reduce the chance of rear-wheel lockup, minimizing oversteer or instability.

2. **Corner Entry:**
   - A properly adjusted braking differential allows the rear of the car to rotate just enough to aid in cornering. This is especially useful in tight rallycross tracks where sharp turns are common.

3. **Traction Management:**
   - On mixed surfaces like gravel, dirt, or tarmac, different traction levels demand fine-tuned differential behavior. Modifying the diff lock on braking helps manage how much torque is distributed to the wheels when traction varies.

4. **Customization for Driver Preference:**
   - Different drivers prefer specific car behavior during braking. Some may prefer a car that rotates more aggressively (looser diff), while others may prioritize stability (tighter diff).

5. **Adaptation to Track Conditions:**
   - Rallycross tracks feature a mix of surfaces and tight, technical sections. Drivers may need to adjust how the differential locks under braking to adapt to specific track layouts or changing conditions during a race.

### **How It's Done**
Modern rallycross cars often use active differentials, controlled electronically or hydraulically. These systems can dynamically adjust the differential locking strength based on:
   - Driver inputs (e.g., braking force, throttle, and steering angle).
   - Pre-set parameters for specific sections of the track.
   - Real-time data from the car's sensors.

By fine-tuning these systems, teams can ensure the car handles optimally during braking, improving lap times and consistency.


the differential settings changes on braking are made suddenly, or gradually?
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The changes in differential settings during braking in rallycross cars can occur either **suddenly** or **gradually**, depending on the type of differential system and the desired driving characteristics.

### **1. Sudden Changes:**
   - **Mechanically Controlled Differentials:**
     In simpler, mechanically controlled systems like Limited Slip Differentials (LSDs), the transition between open and locked states can occur relatively suddenly. For example:
       - When braking force exceeds a certain threshold, the differential may quickly shift to a looser or tighter state.
       - This sudden change helps create a sharp and predictable response, which some drivers prefer for initiating precise handling adjustments, such as a quick car rotation during corner entry.

   - **Electronically Controlled Differentials:**
     In advanced rallycross cars with electronically controlled diffs, the system can be programmed to change settings instantly at specific trigger points, such as when brake pressure reaches a set level or the ABS activates. These quick adjustments allow the car to respond rapidly to dynamic conditions.

### **2. Gradual Changes:**
   - **Progressive Locking/Unlocking:**
     Some systems, particularly advanced active differentials, allow for a more gradual transition in locking strength. These systems monitor variables like brake pressure, steering angle, wheel speed differences, and yaw rate. The locking force can be smoothly modulated based on the situation.
       - For example, as brake pressure increases, the differential may progressively unlock to enhance stability and reduce wheel hop or skidding.

   - **Driver Preference:**
     Some drivers prefer a smoother, more gradual change in differential settings to maintain a predictable car behavior during braking, especially on slippery surfaces like gravel or snow.

### **Which Approach is Better?**
   - **Sudden Changes** are better for aggressive driving styles or situations where quick reactions are needed, such as tight corner entries on high-grip surfaces.
   - **Gradual Changes** are better for maintaining control and stability, especially on mixed or low-grip surfaces where sudden adjustments can cause unwanted oversteer or understeer.

### **Conclusion**
In modern rallycross cars with advanced systems, the approach is often programmable. Teams adjust whether differential changes occur suddenly or gradually based on track conditions, driver preferences, and vehicle dynamics.