For some reason only rear wheels are so stiff, bouncy yet stable. I think hubs are the cause, because without tires they are still unreasonably hard and causes bounciness. I checked everything I could think of at this point. Does anyone have an idea what might be wrong? I'll put the vehicle folder link. https://ufile.io/nl3cm
It could be collision triangles, if nodes of axle/hub are colliding with some collision triangles, you get rear suspension that is not moving much and acts like how you describe. That is without checking the file, sorry had no time now, but at least something you can check out.
I uploaded a video, have a look, I it's not collision triangles that is causing this, unless hub wheels have those? I doubt. I uploaded a video of showing what I described. Have a look, it's not collision triangles that is causing this. Also the stress visualization of rear tire differs a bit compared to the front, the colors are more contrasted on outer edge and softer on side surface, my guess the hubs are causing this.
Oh, by looking the video, it appears to be mass/spring/damping related. You have lot less weight on other set of tires, so they would need lot less spring to behave same as other set. However as your axle is not attached to rest of the vehicle, there is very little weight, but once you attach axle and increase mass, those should start behaving better.
Yeah, once I separated the front axle it was stiff and bouncy too. Adding more weight and tweaking springs a bit made it smoother. TY.