Just changing the Audi timing belt isn't enough. Why? Most Audi timing belt failures can be caused by worn timing belt tensioners and idlers. If you just replace the Audi timing belt, a thousand miles later it can fail due to a worn timing belt tensioner, idler or roller and still cause major engine damage. Not replacing ALL Audi timing belt components can be very dangerous. This is because the Audi timing belt tensioner pulleys or rollers may visually appear to be fine, but may actually be near or at the end of their service life. That is why the Audi timing belt tensioner and idlers should always be replaced when installing a new timing belt. Skipping their replacement is a hazardous choice. This probability is also the reason why some Audi mechanics recommend performing the Audi timing belt replacement before 60,000 miles instead of 90,000 miles.