Troubleshooting the kart plugin | UE5 Kart Physics docs

Find your symptom below. Each entry names the usual cause and the fix.

Setup and driving

The kart does not move

Cause: no player controls the kart, so your input goes to another pawn (or nowhere).

Fix: select the kart in the level and set Auto Possess Player to Player 0 in the details panel. Or select BP_KartPawn as the Default Pawn Class of your game mode. See Getting started.

Smearing while drifting

Cause: temporal anti-aliasing (TSR or TAA) blends several frames, which smears the fast sideways motion of a drift.

Fix: in your project settings, disable TSR and TAA and use something else, like FXAA, for anti-aliasing. The setting is Anti-Aliasing Method in Project Settings > Rendering > Default Settings. The example project already uses FXAA.

The kart behaves differently at another framerate

Cause: the kart is tuned for a fixed 60 Hz physics tick. Without Tick Physics Async, the physics steps with the frame time, so the handling changes with the framerate.

Fix: in Project Settings > Physics > Framerate, check Tick Physics Async and set Async Fixed Time Step Size to 0.016667 (60 Hz).

You want another physics rate on purpose: turn on Tick Rate Independent Acceleration (Kart Base Settings > Acceleration), then re-tune. All other defaults are still tuned for 60 Hz. Coming in 1.1
Wheels or lean micro-stutter on a 120 Hz or faster display: check that Smooth Visual State is on (Kart Base Settings > Visual Smoothing, on by default). See Visual smoothing. Coming in 1.1

Why the kart needs a fixed step: async physics in Unreal Engine, on the blog.

Surfaces or offroad have no effect

Cause: usually the ground’s Physical Material has a different surface type than the one you set up. For example, the material uses SurfaceType2 while the project named SurfaceType1 “Offroad”.

Fix: check these in order.

Project Settings > Physics > Physical Surface: note the name of your surface, for example Offroad.
Open the ground’s Physical Material: its Surface Type must be exactly that surface.
Check that this Physical Material is assigned to the ground you drive on (in its material or landscape layer).
Check that Surface Properties (Kart Base Settings > Surfaces) has a row with that Surface Type. An empty list turns the feature off. Coming in 1.1

The kart only hops and does not drift

You are not steering. A drift starts only when you press the drift button while steering left or right. Without steering, the kart just jumps.
The kart is too slow. Below Minimum Speed Needed for Drift (Kart Base Settings > Drifting) the press is a plain jump, and a drift that falls below it ends.

See How a drift works.

Multiplayer

Multiplayer is part of version 1.1. Coming in 1.1

Karts drive into or climb onto each other in multiplayer (1.1)

The required ini line is missing. Check this first. Without it, karts can drive into each other after a network correction, then get pushed apart upward. Fix: see the red on-screen message below.
Kart Collision Mode is Ignore on either kart: the two karts pass through each other on purpose. Use Arcade Bump or Physics on both.
Suspension Ignores Other Karts is off: the suspension treats other karts as ground, so a kart can ride up onto another. Turn it back on (the default).

See Kart collisions.

Other karts look delayed in multiplayer testing (1.1)

Emulation Target is Everyone: every packet is delayed at both ends, so the round trip roughly doubles. In Play > Advanced Settings > Multiplayer Options, set Emulation Target to Server Only and Network Emulation Profile to Average (30 to 60 ms each way). Type stat net in a client window to see the real ping.
Some delay is normal: another player’s input reaches you a round trip late, so their taps, brakes and turns show up as small corrections.

See Multiplayer setup.

Red on-screen message about AccelerationStructureCacheOverlappingLeaves (1.1)

In development builds, a networked kart prints this in red once, and the Output Log shows it as an error. The message starts with:

KartDriftingPhysics: networked Kart collisions need p.Chaos.AccelerationStructureCacheOverlappingLeaves=0.

Cause: Unreal Engine 5.7 skips refreshing a physics cache while it replays a correction, so karts can drive into and over each other. The setting must be active before the physics scene starts, so the plugin cannot switch it for you.

Fix: add this to Config/DefaultEngine.ini (if the section already exists, add the line to it), then restart the editor. Typing it in the console at runtime is not enough.

[ConsoleVariables]
p.Chaos.AccelerationStructureCacheOverlappingLeaves=0

Single player games do not need it.

Still stuck?

Ask on Discord. Tell us your Unreal Engine version, the plugin version, whether it happens in single player or multiplayer, and what you see. Comparing your settings with the example project often finds the difference fast.