Thule Frame Adapter - Bicycle Cross Bar. Get it as soon as Tue, Sep 15. FILTERS. Gender. 4.3 out of 5 stars 736. You're not alone — most cyclists don't know much past how to add air (and even that can sometimes be tricky). Red. It attaches to the seat tube and stem, creating a durable top tube that allows your bike to fit onto your car rack safely and securely.