[tuff_girl]

Both the Thule 400XTR Rapid Aero Complete Roof Rack Base System and the Thule 400XT Aero Complete Roof Rack Base System will fit your 2004 Audi s4 perfectly and are very quick to install, just follow the easy install instructions. No matter what gear attachments you plan to carry on your roof, you will need a multi-purpose roof rack base system. The sleek looking Thule 400XTR Rapid Aero system includes four 400XTR Aero feet, four FitKit 249 Clips (specific to your 2004 Audi s4) and two Rapid Aero load bars (please note you will need to choose the 47" length elliptical Rapid load bars for your roof top). Likewise the more classic looking Thule 400XT Aero system includes four 400XT Aero feet, four FitKit 249 Clips (specific to your vehicle) and two square load bars (please note you will need to choose the 50" length square load bars for your roof top). You will attach the bike carriers to the front and rear load bars on either of these systems. Once you've installed either of these car racks systems as your Audi s4 roof rack system you can then connect any of Thule Racks bike racks. I prefer the Thule 594 Side Arm for rapid quick loading of any style of bike, no need to take the front wheel off or anything either.