Cars in Forza Horizon are categorized into different performance classes, ranging from D (lowest) to S (highest), with additional subclasses like A, B, C, and R. Each car also has a Performance Index (PI) number, which is a more granular representation of its overall performance within its class. For example, a car might be in Class A with a PI of 750. When entering events, you'll often be restricted to specific car classes or PI ranges. It's crucial to understand these classifications when choosing and upgrading your vehicles. A higher PI generally means better acceleration, top speed, handling, and braking. You can upgrade your car's PI by installing performance parts in the 'Garage' under the 'Upgrade' section. Experiment with different upgrades to find the optimal balance for various race types. Sometimes, a well-tuned car in a lower class can outperform a poorly tuned car in a higher class, so don't just chase the highest PI number blindly.
