I've been working on a car prototype myself and I've had more success not using colliders for the wheels at all.
I don't wanna link a video in a comment here but if you find "Space Dust Racing UE4 Arcade Vehicle Physics Tour" on youtube, that video was really enlightening to me on how to make simple car physics (in any engine), even if you want less arcadey feeling, I've found a lot of other tutorials that dug further into it but that basics laid out in the Space Dust video are solid and gave me a lot better understanding.