We can offer you lots of choices in roof-rack-mount bike carriers for use on your 2015 Audi S3. Before you commit to a dealer-installed OEM type rack you might want to consider one of the aftermarket systems shown on the linked page. Options include round, square and aero-style crossbars and racks systems for your S3 are available from quality brands like Yakima and Thule.
Often the aftermarket racks will be priced much lower than OEM alternatives, just something to consider unless you're... view full answer...