Don Johnson

I have a 2006 Cannondale T-800 with a stock drivetrain that consists of Shimano 105 9-speed shifters, Tiagra FD and Truvativ Blaze triple (26-36-48). All I want is a lower granny gear than the 26-34 that I currently have but have never been able to get a definitive answer as to whether that is a simple job or not. Can someone answer that question in layman's terms please?

Thanks, in advance, for the replies.