2D car brakes help???

hello im having trouble with my brake system when i press space and S the car flys off and it only works forward but not backwards this is really made me mad and cant find the answer :|

heres the code

 using UnityEngine;
 using System.Collections;
 
 public class NewBehaviourScript : MonoBehaviour {
 
     public float speedF = 10f;
     public float speedB = 10f;
     public float mph;
     public Vector2 hat;
     public float throttle;
     public float moderation = 0.5f;
     public float decrease = 0.3f;
     public bool braked = false;
     public bool brakeS = false;
     public GameObject wheelB;
     public GameObject wheelF;
     private Vector2 speed = new Vector2(3, 0);
     
     void Start()
     {
 
 
     }
     void OnGUI(){
         
         mph = rigidbody2D.velocity.magnitude * 1;
         
         Debug.Log("Mph: " + mph);
 
     }
     void FixedUpdate()
     {
         handBrake ();
     }
     void Update () {
 
 
             throttle +=Input.GetAxis("Vertical")* 50;
             throttle -= decrease;
             throttle  = Mathf.Clamp(throttle,0,25);
             print (throttle);
             
          
         if(Input.GetKey(KeyCode.W))
         {
 
             wheelB.rigidbody2D.AddTorque(throttle);
 
 
         }
         if(Input.GetKey(KeyCode.S))
         {
             wheelB.rigidbody2D.AddTorque(-speedB);
 
         }
     
     }
     void handBrake()
     {
         if(Input.GetButton("Jump"))
         {
             braked = true;
         }
         else
         {
             braked = false;
         }
         if(braked)
         {
                 //wheelB.transform.rotation = Quaternion.identity;
                 //wheelB.rigidbody2D.AddTorque(-mph * 10);
         
             wheelB.rigidbody2D.AddTorque(-mph * 10);
 
         }
         
         
     }
 }