Ok… So what is it that you exactly want? Roblox’s example has a different approach to the equations than I do. UpdateThruster function in the LocalCarScript is the place where it does that.
--If we're on the ground, apply some forces to push the wheel up
bodyThrust.force = Vector3.new(0, ((stats.Height.Value - thrusterHeight)^2) * (force / stats.Height.Value^2), 0)
local thrusterDamping = thruster.CFrame:toObjectSpace(CFrame.new(thruster.Velocity + thruster.Position)).p * damping
bodyThrust.force = bodyThrust.force - Vector3.new(0, thrusterDamping.Y, 0)
but the one I suggested would have more realistic physics.