Originally Posted by DocRay
I've never seen a single manufacturer ever recommend different PSI for weight, they all say run at recommended, usually 120psi for clinchers.
lower pressure may be more comfortable, but prepare for more cuts and flats, and greater rolling resistence.
Something like 60% of the weight is on the rear tire so it makes sense. Sheldon Brown says:
Since most bicycles have substantially more weight on the rear wheel than on the front, the rear tire should almost always be inflated to a higher pressure than the front, typically by about 10%.