Handling is kinda bad after getting new rear tires - change the fronts or the brand

[Racer Boy]

Sounds to me like you have mismatched tires. If new rear tires are the only change you've made to the car, then that is the only possibility. I'm not familiar with either tire model you are running, but it's likely that the new rears don't have as much grip as the used fronts (or vice versa). I bet if you get new fronts to match the new rears, your problem will be solved.