The MaxxRaxx bike rack supports and securely grips the top-tube of your bicycle. Almost all bikes are compatible with the MaxxRaxx system. However, certain bikes that have no top-tube such as full suspension Y-frame mountain bikes or "step through" ladies bikes (without a cross bar) may require an X-bar, available from our Accessories section. This enables a bike without a top-tube or cross-bar to be carried on the MaxxRaxx cycle carrier.