Physics based kart is applying force forward-only issue:

[7Delta (Delta)]

Hello, I’m trying to recreate Mario Kart 8’s kart movement in Unreal Engine 5.6.1 and when I apply force ONLY straight-forward (just pressing the W key) something weird happens:
(Watch until the end)

Basically, for some reason when applying force forward, the kart rotates a bit to the left or right and sometimes it rotates too much (like seen in the video).

Here is how I have it setup:

Project gravity Z: -3500,0

[dZh0]

I think there is a subtle change in the terrain geometry which hits one side of the cart for the sudden turn. Also there might be some barely noticeable incline that makes the car turn as it goes.

Try it on a simple flat box and do tell if it behaves better.

[7Delta (Delta)]

In a flat box behaves well. However, if i want to make a landscape the issue will still occur. Is there a solution for that?

[dZh0]

You will get the best result if:

• Use physics based vehicle solution like Chaos Vehicle or PhysX vehicle. (physX will still need considerable amount of integration)
• Implement your own simplified physics vehicle movement. (works if you are making a simple game)

Before doing that though, try to minimize your contact with the ground. Make your wheels sphere colliders or something similar to avoid one wheel hitting an edge. I think this is what makes the sudden turn. Make your whole cart use one sphere collider if you can get away with it.

Also, try to introduce some friction to avoid sliding sideways down the slope. I think this makes your car slightly turn no uneven terrain. To be honest the friction part is the key here as wheels have very high “move sideways” resistance and almost none in the direction they roll.