Probelms with wheels going trough terrain and objects

Alright, so i got the buggy working as the player, so the player spawns as a car

then
i jsut changed the shape of the car dts file. and now the car tips over, or when it doesnt and i drive, the front wheels dig into the ground until u cant drive it, or randomly a wheel goes trough the terrain and then alll hell breaks lose


could some one please explain to me why this is happening?? exspecially the wheels trought he terrain

shouldnt they always stay on the terrain? im using the buggy wheels so why is it behaving wierdly??