How to Fix Vehicle Drift From a Physics Substep Mismatch in Unreal

Your car handles fine at 120 FPS but slides unpredictably at 30. The physics step length tracks the frame time, so integration error scales with frame rate. Enabling fixed substepping makes handling deterministic.

How to fix it

1. Enable substepping

In Project Settings / Physics turn on Substepping so the engine runs multiple fixed-size physics steps per frame instead of one variable-length step.

2. Set max substep delta

Configure Max Substep Delta Time (e.g. 1/120) and Max Substeps so each physics integration covers a consistent time slice regardless of render frame rate.

3. Apply forces in the substep callback

Apply vehicle and custom forces inside the async physics / substep tick rather than the game tick so they are integrated at the fixed substep rate.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every Unreal Engine error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.