Powerslide Kart Physics
This is the most straightforward solution for achieving smooth, responsive kart physics. Familiar mechanics including jumping, drifting, and turbo boosting are all here, along with limited item/powerup support and basic waypoint AI.
More Info + DemoDocumentationDownload Unity PackageDownload on GitHubConvex Collider Creator
Tired of tediously modeling collision meshes from scratch in external software?
Sounds like you need Convex Collider Creator, a flexible tool for crafting convex mesh colliders in the Unity Engine. The powerful editor window and collider group component allow you to nondestructively design multiple colliders at once and generate them both in the editor and at runtime.
Randomation Vehicle Physics
An open source vehicle physics package for the Unity Engine supporting many vehicle configurations, damage, and stunt detection. It’s designed to achieve a semi-realistic balance in handling and comes with many prefab vehicles ready to customize.
Download on GitHubDocumentation