Originally Posted by cyccommute

I have problems with some of the points in this video. The first is the statement that tire pressure is set to 1/2 the blowoff value of a "standard rim". I've heard this stated in lots of places but I have yet to find a credible citation of where that comes from. Yes, it's higher than the maximum pressure but twice as much? I find that very hard to believe for all tires in all widths and all possible rim widths. I've had tires that blew off at the nominal highest pressure setting.

Going over to the Silca calculator, I have definite problems with their pressure. While some of the pressures would be valid for racing conditions, they become invalid for people who have to actually pay for their parts rather than have a sponsor. The suggested pressure for a mountain bike for me is 23 and 24psi front/rear, respectively. If I add a bikepacking load of 40 lbs, the pressure suggestion is 26 and 28 psi, front/rear. First, I've ridden tires that have that little pressure in them for off-road without a load and it wallows. It doesn't turn well. But, more importantly, that kind of pressure is going to result in the tires bottoming out on hard edges which risks not just a pinch flat but a damaged rim. I've seen some very nice rims ruined because someone was using the "optimum" ride pressure and completely ignoring the other function that tires serve...to protect the rims.