public void update(float delta, boolean accelerating) {

   float speed = v.length();

   Main.renderStringFormatted(29, "%d", (int) rpm);
   Main.renderStringFormatted(30, "%d", gear + 1);
   Main.renderStringFormatted(0, "Geschwindigkeit: %.1fkm/h", speed * 3.6);

   rpm = wheelSpeed * vehicle.getGearRatio(gear) * 30 / Constants.PI;
   if (rpm < vehicle.getMinimumRPM())
      rpm = vehicle.getMinimumRPM();
   if (rpm > vehicle.getMaximumRPM())
      if(shiftGearsUp())
         rpm = wheelSpeed * vehicle.getGearRatio(gear) * 30 / Constants.PI;
      else
         rpm = vehicle.getMaximumRPM();

   float Fdrive = vehicle.getEngineTorque(gear, rpm)
         / vehicle.getTireDiameter();
   Vector2f Ftraction = accelerating ? dir.mul(Fdrive) : new Vector2f();
   Vector2f Fdrag = v.mul(-vehicle.getShapeDrag() * speed);
   Vector2f Frr = v.mul(-vehicle.getShapeDrag() * 30);

   Vector2f Flong = Ftraction.add(Fdrag).add(Frr);

   Main.renderStringFormatted(1, "LW-Kraft: %.1fN",
         Fdrag.lengthSigned(dir));
   Main.renderStringFormatted(2, "RW-Kraft: %.1fN", Frr.lengthSigned(dir));

   float Wr = vehicle.getBackTireLoad(Flong.lengthSigned(dir)
         / vehicle.getMass())
         / (vehicle.getMass() * 9.81f);
   Main.renderStringFormatted(5, "Load V: %.2f%s", Wr, "%");

   Flong = Ftraction.mul(Wr);

   Vector2f Ffriction = new Vector2f();

   if (speed > 0) {
      float slip = (wheelSpeed * vehicle.getTireDiameter() - speed)
            / speed;
      Main.renderStringFormatted(4, "Slip: %.2f", slip);

      Ffriction = Ftraction.mul(Math.min(16.6666667f * slip, 1));
   }

   Flong = Flong.add(Frr);
   float Tfriction = Ffriction.lengthSigned(dir) * vehicle.getTireDiameter();
   float Tdrive = Flong.lengthSigned(dir) * vehicle.getTireDiameter();
   float Ttotal = Tdrive - Tfriction;
   float aa = Ttotal / vehicle.getRearTireInertia();
   wheelSpeed += aa * delta;
   Main.renderStringFormatted(6, "Tfriction: %.2fNm", Tfriction);
   Main.renderStringFormatted(7, "Tdrive: %.2fNm", Tdrive);
   Main.renderStringFormatted(8, "Ttotal: %.2fNm", Ttotal);
   Main.renderStringFormatted(9, "Angular acc.: %.2frad/s^2", aa);
   Main.renderStringFormatted(10, "Wheel vel.: %.2fkm/h", wheelSpeed * vehicle.getTireDiameter() * 3.6);
   
   Flong = Flong.add(Fdrag);
   Vector2f a = Flong.div(vehicle.getMass());

   Main.renderStringFormatted(3, "Beschl.: %.2fm/s^2", a.lengthSigned(dir));

   v = v.add(a.mul(delta));
   if (dir.dot(v) < 0)
      v = new Vector2f();

   pos = pos.add(v.mul(delta));
}