Even for the wheels i swapped to parts instead of meshes to get a even more perfect geometry, but its still bouncy.
However, when i drive on a baseplate or a singular part the car doesn’t bounce, its only when there are lots of consective small parts. I tried things like grouping the map as union, which does help but it still randomly bounces at times.
This is expected behavior, no physics engine can process distant colliders quickly enough to realize that at the next physics step there will be a colission at that far away object. I can only suggest against using seperate parts for flat surfaces, you can achieve so by unioning the set of parts and setting the ColissionFidelity to Hull or PreciseConvexDecomposition. You can see how they look here or via the option in the studio (I recomend the studio’s default colission viewer over any kind of plugins as they do not work on mesh parts):
