So, now that I have those Ortlieb backroller panniers everyone was so kind in pointing me to, what should I know about loading them? I used them yesterday to haul a ton of books back to the library and today to haul groceries, and they are truly da bomb. I am wondering, however, what I should know about handling the bike with heavy panniers or if there are effects I'm not aware of (what does it do to your tire life, for instance, to ride with a heavy load? Should I change the pressure in my tires since the load adds many pounds to my weight? How heavily can I load them without adverse effects?). Tips/tricks/traps?