The brake pads work with the brake discs to slow your Audi A4 down by applying friction. Over time these wear down and require replacing to give you optimum braking, keeping you and other road users safe. You may find that as the pads wear down there is a metalic sound upon braking on pads using an acoustic wear indictor or a warning light on the cars dashboard for those that use an electronic wear sensor. This would indciate that your brakes need changing. If you need to replace your pads then orangespanner hold large stocks to suit all budgets.