Heading west along chambers st until you get to the end of the old college building a little cobbled lane runs between old college and the museum turn left up the lane. About half way up on the left hand side is a door, a big door but definitely a door, it is usually open. You can wheel your bike through and you are then on the terrace around what use to be the old college car park and is now the warriors light show. Rackets are down three steps.
If going in the main entrance can you not take a right and cycle on to the terrace and cycle round to the racks. I am not suggesting this as it is a bit like a pavement. Just take my route. Tis is also always the way I would go in to the Talbot rice Gallery, well when I were a nipper and went to that gallery.