I changed my brake pads a while back and the new pads rattle. The pistons push against the pads, but the pads rattle up and down inside the calipers. I just changed brake pads on a friend's car today and noticed that he had some retaining clips that went inside his calipers to hold the brake pads more tightly. Is my 98 blazer supposed to have these? Or can you buy them aftermarket?