MotorVehicle - Chassis Programming Made Easy


Chassis Programming Made Easy


Programming chassis in video games is a very overwhelming, difficult, as well as tedious process that is hard to get it just right, this library was written to solve this problem. It’s also a great place to dissect the code to learn on how to write your own chassis.

If you are planning on making a realistic car racing game, it’s probably best in your interest to avoid this library as it is not meant to be used in racing games. But if you are making a game like Bloxburg, Emergency Response: Liberty County, or something that doesn’t primarily focus on motor vehicles and you want to save yourself some time, this is probably a library for you.


Getting Started

You will need to get the library and initialize a new instace of the class.

Source Code: GitHub
Roblox Model: Roblox
Example Place:
MotorVehicle Example Project.rbxl (764.4 KB)

local bus ={
	root = VehicleSeat,
	wheels = {Chassis.RL, Chassis.RR},
	torque = 1000,
	maxSteerAngle = 45,
	turnSpeed = 3,
	gearRatio = {2.97, 2.07, 1.43, 1.00, 0.84, 0.56},

And whenever you are ready, you can compute properties via the method below:

local output = bus:compute(deltaTime, {
	steerFloat = -VehicleSeat.SteerFloat,
	throttleFloat = VehicleSeat.ThrottleFloat

You will need to know how to rig a vehicle before doing this, I highly recommend watching this tutorial.

Initialization Configuration


Type: BasePart

The most important part of the vehicle, it will be used to determinate certain things like direction, speed, etc.


Type: {BasePart}

An array of wheels that will be driven (aka “powered”) by the motor, those will be used to determinate certain states, the library will not drive them, that will be your job to do so.


Type: number (preferablly an integer)

The measurement of your car’s ability to do work, meaning that the more torque, the greater amount of power an engine can produce. If your engine has a lot of torque, your car can accelerate more quickly when the vehicle is beginning to start (explanation taken from kia website).


Type: number (preferablly an integer)

Determinates how far the wheel can be turned (angle in degrees).


Type: number

Arbitrary number which defines the top speed at which the wheels can turn.


Type: {number} (preferablly a float)

Ordered array of floats that determinate ratio per gear (their order matters as the system takes ratio from the left side and as the gear goes up the index which is used to take the gear ratio will also increase, move to the right).


Image source:



Returns: number

Computes pitch for the engine sound. Make sure to perform extra math operations on the returned value to suits your specific audio (eg. pitch + 0.5). It automatically clamps the number to prevent large spike when vehicle falls or glitches out (aka you won’t go deaf when the car glitches out at 3000 studs per second).


Returns: number

Determinates the vehicle speed and returns it. The returned value is always positive as your day should be :) (no pun intended)


Returns: number

Determinates whether the vehicle is in neutral, breaking, or accelerating. You can take the returned value and compare it against an ThrottleState enum included in Enums module script.


getThrottleState() == Enums.ThrottleState.Breaking

Returns: number

Determinates whether the vehicle is going forward, backwards, or is resting in place.

  • 1 moving forward
  • 0 resting in place
  • -1 moving backwards


	angularVelocity: number, -- Angular velocity to be applied to vehicle's motor(s)
	angle: number, -- Turn angle for the wheels
	motorMaxTorque: number, -- Maximum torque that the vehicle's motor(s) can run at
	motorMaxAngularAcceleration: number -- Maximum angular acceleration that the vehicle's motor(s) can have


deltaTime: number,
config: { steerFloat: number, throttleFloat: number }?

Computes values required to make the vehicle react to a given input.


for _, wheelAtt in wheelAtts do
	wheelAtt.Orientation =, output.angle, 90)

for _, motor in motors do
	motor.MotorMaxAngularAcceleration = output.motorMaxAngularAcceleration
	motor.MotorMaxTorque = output.motorMaxTorque
	motor.AngularVelocity = output.angularVelocity

This looks cool! I’ll try it out once I find the time :slight_smile:

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Great to hear! I am also planning on adding example project but I need to clean up some of my old messy testing code.

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This is something I need. Thanks for making it!

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Whats the benefit over other existing chassis such as A-Chassis or AG-Chassis which is what some of the games you mention use(modified versions at least).

  • It’s simple; therefore, easy to dissect.
  • It’s lightweight.
  • It’s open-source, anyone can contribute.
  • It’s a library, not a full working out-of-box system that you need to configure and write plugins for. Therefore, you have the full control.

A-Chassis is advanced system, feature-rich, works out-of-box with lengthy configuration, you have to follow it’s rules to make it work.

On other hand, MotorVehicle is a library, needs to be interacted with code and it doesn’t force anything upon your chassis, so you can make your chassis structure how you like it. You simply feed it with information, and it spits out information to you, then can use the output how you wish to.


You should add this into your post, they are all good selling points.


looks interesting!
i may try to add this to my game :+1:

Release 2.0.0

What’s New?

  1. Made wheel retract their turn angle faster when player stops turning.
  2. Renamed and added some API methods to make it more consistant.
  3. Added documentation comments.
  4. Added example project with 3 vehicles.
  5. Added chassis stats to the example project.

API Changes:

  1. getPitch() has been renamed to getRevPlaybackSpeed()
  2. getSpeed() has been renamed to getAssemblyVelocity()
  3. getThrottleState() has been renamed to getAssemblyVelocityState()
  4. getDirection() has been renamed to getAssemblyDirection()
  5. gear has been replaced with getGear()
  6. engineRPM has been replaced with getMotorRPM()
  7. getMotorHorsepower() has been added
  8. torque has been replaced with getMotorTorque()

What’s next?

I am working on 10th generation of the chassis where constraints will be replaced with pure math and raycasting, it should enable greater control of the chassis feel without it tilting/rolling over at high speeds.


How well does this function with fluctuating or low FPS? There have been times whilst working with chassis that a user’s FPS will affect how well the chassis functions.

Are you talking about the current chassis? If yes, then FPS should not affect how the chassis behaves because it’s relying on Roblox’s constraints.

On the other side, the upcoming chassis will be using raycasting, which so far is unfortunately affected by FPS because Roblox doesn’t give us frame rate independent loop with fixed delta like Unity does with it’s fixed update function. I am not sure how to solve it yet but I am leaving it for later since it’s not important at the moment.

But, here it how the raycast chassis looks so far:

It still needs gearbox, and all that fancy stuff that the current chassis has.

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Looks awesome!

Since the upcoming system will be using raycasting.
Does this mean that this system also can be used to create vehicles without wheels like hover cars or vehicles with two wheels?

Since I’m assuming you are using raycasting to adjust the height and balance of the car and not the actual physical wheels?



Here is more progress:


API v3 Design Draft


local Players = game:GetService("Players")
local RunService = game:GetService("RunService")

local CarController = require(packages.CarController)

local model = script.Parent
local driverSeat = model.DriverSeat

local car =

local heartbeat

local function serverControl()
	-- Remove network control from the player, let server do it

	-- Handle the wheels
	heartbeat = RunService.Heartbeat:Connect(function(deltaTime)
		local steerFloat = 0
		local throttleFloat = 0

			steerFloat = steerFloat,
			throttleFloat = throttleFloat,
			deltaTime = deltaTime

local function clientControl(player: Player)
	-- Give network control to the player

	local client = script.Client:Clone()
	client.Parent = player.PlayerGui
	client.Enabled = true

	-- Revoke server control, if any
	if heartbeat then

car.onOccupantJoinedSeat(driverSeat, function(humanoid)
	local character = humanoid.Parent
	local player = Players:GetPlayerFromCharacter(character)

	-- We only want players to use the car, not NPC's, etc.
	if not player then


car.onOccupantLeftSeat(driverSeat, function()

-- By default the server will control the car
local RunService = game:GetService("RunService")

local CarController = require(packages.CarController)

local model = script.Vehicle.Value
local driverSeat = model.VehicleSeat

local config = require(model.Config)

local car =


-- Handle the wheels
local heartbeat
heartbeat = RunService.Heartbeat:Connect(function(deltaTime)
		steerFloat = driverSeat.SteerFloat,
		throttleFloat = driverSeat.ThrottleFloat,
		deltaTime = deltaTime

	model.Root.Engine.Rev.PlaybackSpeed = car.engine:getRevPlaybackSpeed() + 0.75
local CarController = require(packages.CarController)
local Wheel = CarController.Wheel

local model = script.Parent

return {
	root = model.Root,
	engine = {
		torque = 3,
		gearRatios = {3.587, 2.022, 1.384, 1.000}
	suspension = {
		height = 1.5,
		stiffness = 200,
		damping = 4
	wheel = {
		radius = 1.25,
		friction = 5.5,
		maxSteerAngle = 30
	wheels = {{
			part = model.Wheels.FL,
			isSteer = true,
			part = model.Wheels.FR,
			isSteer = true,
			part = model.Wheels.RL,
			isSteer = false,
			part = model.Wheels.RR,
			isSteer = false,

I want to know what you guys think about this API design, things like:

  • What to improve
  • What to add
  • What to remove

And any other thoughts you might have.


Whoa, you’ve just singlehandedly shot down my single biggest excuse for not revamping my own NGChassis project from a few years back: transmission math. You good with me integrating this into that project and publishing it?

Yes, because It’s under the MIT license.

Could you also make it compatible with R6? Because when I tested it in only seems to work with R15.

Are you sure? What happens when you use R6?

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When I enter the car my head is flying above it, and when I leave the car, my face is gone.

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How is this going are you still working on it?