Adjustable rack assemblies and end caps for appliances, such as a dishwasher appliance, is provided herein. A rack assembly may include a frame, a rack, a first front wheel, a second front wheel, and an end cap. The rack may be selectively mounted to the frame to receive articles for washing within a wash chamber, and may be slidable along the frame between an extended position and a retracted position. The first front wheel may be rotatably attached to the rack above the frame. The second front wheel may be rotatably attached to the rack below the first front wheel in vertical alignment therewith. The end cap may be attached to the frame at a forward end thereof. The end cap may define a top-end catch profile and a bottom-end relief profile.