So how far can I air down my stock Rubi tires. So far, I haven't gone any lower than 15psi. It looks like I'm gonna be snow wheeling this weekend, and I'm not sure if it's safe to go lower. I don't want to risk blowing a bead, but a little less air might help.

With the stock rubi tires I had on before I aired down to single digits on more than one occasion and never blew a bead.. But that's low for those tires. In hindsight I probably shouldn't have. I found that if I really needed traction, 11-12 psi worked well.. If I was just doing a trek out I'd air down to 15 and then air down more if I needed more traction further down the trail.