Need help with controller script.

I am trying to work on a more simple car script for a place holder in my project.

The concept is simple, while W is held down, then curSpeed++ until it reaches the maxSpeed. while curSpeed is greater than 0 it will addforce(value being curSpeed) to the rigidbody making it move forward. Now that works great and suprisingly enough its more realistic than I had thought it would be lol. But now stoping the vehicle is the issue. I press SPACE and it stops the accelerator and makes curSpeed-- but its not seeming to work. I am probably making a simple mistake but a set of more experienced eyes would be appreciated. Here is what I have so far.

 using UnityEngine;
 using System.Collections;
 
 public class CarController : MonoBehaviour {
 
 
     public int fuel;
     public int maxFuel;
 
     public float curSpeed;
     public float maxSpeed;
 
     public float accelRate;
 
 
     // Use this for initialization
     void Start () 
     {
         fuel = maxFuel;
     }
     
     // Update is called once per frame
     void Update () 
     {
         Bounds();
  
         if (fuel > 0)
         {
 
             if (Input.GetKey(KeyCode.W))
             {
                 print("Accelerating.");
                 curSpeed++;
                 rigidbody.AddForce(0,0,curSpeed);
             }
             if (Input.GetKey(KeyCode.Space))
             {
                 print("E-Brake Applied.");
                 curSpeed--;
                 //I know something else needs to go here I just can't think of what.
 
             }
         }
     }
 
     public void Bounds()
     {
         //I know mathF.Clamp idk why I am using it this way.
         if (curSpeed >= maxSpeed)
         {
             curSpeed = maxSpeed;
         }
         if (curSpeed <= 0)
         {
             curSpeed =0;
         }
 
         if (fuel >= maxFuel)
         {
             fuel = maxFuel;
         }
     }
 
 
 }