More traction and speed, don't we all want that? I'm 235lbs and for my tubed 26er dual sus I run 28-30 in the front and about 32 rear. On 2.5 inch tires. Less than that and I will pinch flat. On my 29er hard tail I run the about the same pressure using velocity p-35's and tubeless, with 2.4 spec. purgatory tires.