pack lighter!
seriously- look at what you are taking and then evaluate if you really need it or not. You won't need everything you think. I evaluated and reevaluated and still took more than I needed. Should have brought more socks and less shirts. Fit it all in the 2 side cases and a 46L top case with room to spare. One of the side cases held nothing but bike specific gear- rain suit, heavier jacket, first aid kit, tire repair kit, etc.
This is of course, is good advice. However, I'm heading to meet some friends at a conference and I'm expected to bring my share of the goods, thus the need for extra space. If I was just packing for myself, I'd easily have enough room for all my gear.