Here's a link to the Bicycle Quarterly article on tire pressure. I have found quite useful. For me, it resulted in using lower pressure than I used to. I am 167, and I run my front 25mm at 70 and rear at 100.
http://www.bikequarterly.com/images/TireDrop.pdf
I believe this calculator uses the same math:
http://www.dorkypantsr.us/bike-tire-...alculator.html
A started using this a couple months ago, and wow!
This is the greatest improvement I've made on my bikes in a long time, and it cost nothing!