I have a pair of Vittoia XGs 34mm wide. I'm ran them at 40psi. After practice, I noticed grass lugged between the tire bead and the rim. Am I running too low of a PSI? Is this an indicator that I might pinch flat?
I would guess that when your tire was flexing grass was able to get stuck in there. May also have to do with the width of your rim in relation to the width of the tire. I'm pretty sure this has happened to me before as well but not on the cross bike. With 32's I've run right around 40PSI front and rear with no issues. I usually run the rear up more around 50 recently though. The 25% of your weight method is actually pretty spot on for what I run after doing the math. I say if you aren't denting rims or getting pinch flats, then you're fine.