I am sure this information is out there, but i couldnt find it... I have TKC80s (110/80-19 and 150/70-17) on my F650 GS twin. This far i have ridden them off-road at street pressures. As my skills progress, (i mean as i try harder stuff) i think reducing the tire pressure would help. What pressures do people run with a similar weight bike and similar tires?