How to Edit JBeam Cars in BeamNG.drive

BeamNG.drive is built around a physics engine that simulates soft-body dynamics in real time — and JBeam is the file format that makes it possible. Every vehicle in the game is defined by JBeam files: structured data that tells the engine how a car's nodes, beams, and collision surfaces behave under stress. If you want to modify vehicle handling, change structural rigidity, or tweak how a car crumples, you'll need to get comfortable editing JBeam files.

What Is JBeam and Why Does It Matter?

JBeam (JSON Beam) is BeamNG's proprietary vehicle description format. It's built on JSON syntax, which means it's human-readable plain text — no compiled binaries, no special exporter required. Just a text editor and an understanding of the structure.

Every vehicle is made up of:

• Nodes — points in 3D space that define the skeleton of the vehicle
• Beams — connections between nodes that simulate structural material properties
• Collision triangles — surfaces the physics engine uses for contact detection
• Flexbodies — the visual mesh layered over the physical skeleton

When you edit JBeam, you're changing the underlying physics model — not just the appearance. That distinction matters a lot.

Setting Up Your Editing Environment

You don't need specialized software, but a few tools will make the process significantly more manageable.

Recommended tools:

JSON doesn't forgive formatting errors. A missing comma or mismatched bracket will prevent the vehicle from loading entirely. VS Code with a JSON linter extension catches these problems before you even launch the game.

Finding the Right JBeam Files 🔧

Stock vehicles are stored in BeamNG's core files, but you should never edit those directly. Instead, use the game's mod system.

For stock vehicles:

1. Navigate to DocumentsBeamNG.drivemods on your system
2. Create a new folder structure mirroring the vehicle's path in the game directory
3. Copy only the specific JBeam file you want to modify into your mod folder
4. BeamNG loads mod files with priority over base files — your copy overrides the original without touching it

For mod vehicles: Mod vehicles are typically installed as .zip files in the mods folder. Unzip the mod, locate the vehicles subfolder, and find the .jbeam files inside.

Always keep a backup of any file before editing it.

Core JBeam Concepts You Need to Understand

Nodes

Nodes are defined with a name, X/Y/Z position, and a set of properties:

["nodeName", posX, posY, posZ, {"nodeWeight": 25}] 

Node weight directly affects inertia and how the physics engine models mass distribution. Increasing a node's weight makes that point in the vehicle heavier — which shifts handling balance and crash behavior.

Beams

Beams connect two nodes and carry properties like spring, damp, deform, and break values:

["node1", "node2", {"beamSpring": 2500000, "beamDamp": 200, "beamDeform": 100000, "beamStrength": 200000}] 

• beamSpring — stiffness; higher values make the structure more rigid
• beamDamp — resistance to oscillation
• beamDeform — the force threshold at which permanent deformation begins
• beamStrength — the force threshold at which a beam breaks entirely

Adjusting these values is how you make a car stiffer, floppier, more fragile, or more resistant to damage.

Hydros and Powertrain

Suspension geometry, engine output, and drivetrain behavior live in separate JBeam sections — often in separate files within the same vehicle folder. Changes to suspension.jbeam affect ride height and damping; changes to engine.jbeam affect torque curves and power delivery.

Testing Your Changes in BeamNG

BeamNG supports hot-reloading of vehicle files during a session:

1. Make your edit and save the file
2. In-game, press Ctrl+R to reload the current vehicle
3. The physics model updates without restarting the game

This makes iteration fast. Change a spring value, reload, drive, repeat.

Use the Node/Beam debug visualizer (available in the game's debug menu) to see your structural changes rendered in real time. Nodes appear as dots; beams appear as lines — green for intact, red for stressed or broken.

Where Skill Level Changes the Outcome 🎯

This is where things diverge significantly depending on your background:

• If you're comfortable with JSON and have read the BeamNG documentation, small targeted edits (stiffening suspension, adjusting break thresholds) are accessible within a few sessions
• If you're modifying powertrain files, you'll encounter Lua scripting woven into the JBeam — a separate layer that handles dynamic behaviors like engine simulation and gear logic
• Building a vehicle from scratch requires understanding node placement in 3D space, beam triangulation theory, and aerodynamic surface construction — a substantially steeper curve

The official BeamNG documentation wiki and the community forums contain reference tables for all standard JBeam properties, which matters because using an out-of-range value (say, an astronomically high beamStrength) doesn't cause an error — it just produces unrealistic physics silently.

The Variables That Shape Your Results

How far you can go with JBeam editing — and how quickly — depends on factors specific to your situation:

• Your existing familiarity with JSON and structured data formats
• Which vehicle you're editing (some have dozens of interdependent JBeam files; others are simpler)
• What you're trying to change — visual tweaks via flexbody adjustments are simpler than reworking structural physics
• Whether you're modifying a mod or a base game vehicle, since mod files vary widely in how they're organized
• Your tolerance for trial-and-error, since JBeam physics tuning is inherently iterative

The same set of edits that takes an experienced modder twenty minutes can take a newcomer several hours — not because the tools are difficult, but because understanding why a physics change behaves a certain way requires time with the system.