The replacement of brake pads depends on how long your pad has been used in your car. Generally speaking if you have drived more than 80000 kilometers on the road, it is the time the brake needs to be replaced. However, if you hear any sound of the wheels when driving, no matter how many miles you have drived, you should replace the brake pads. If you're not sure how many miles you've been exercising, you might go to the store to replace the pads, or go to the car service shop to install them.