When I started I actually rode with tubes around 27psi any higher and the chatter was tough at speed and the tires bounced off of everything. Again I am 6' tall and with pack about 220# I am running 2.4 Maxxis Ardents up front and 2.25 in back and they are 29ers. Since I have gone tubeless I have run down around 20 a few times but didn't like the roll over, but the traction was awesome! It seems with my weight 25psi works well for me, although every now and then I can feel the rim hit on some hard square edges, but only on the rear tire where all my weight is!