Originally Posted by msu2001la

Every tire, rider and course is a bit different, so it's something you should experiment with, but generally speaking your teammates are probably correct in saying that 30-35psi will be faster than 40+, assuming you can run that low of a pressure without pinch flatting. Lower psi will smooth out the ride and roll faster over bumps, give you more traction in wet/mud, but it also comes at a greater chance of pinch flatting. This is the basic risk/reward factor in CX tire pressure.

Generally you want to run the lowest psi possible. Clinchers with inner-tubes pinch flat much easier than tubulars, and they also have stiffer sidewalls so the benefits of running them at ultra-low pressures more diminished and also come with higher risks. Keep going down this rabbit hole and you'll quickly learn why tubulars are so popular for CX.

I weigh around 165lbs and 35psi is about the minimum I feel comfortable running my 33mm clinchers, but I'll run as low as mid 20's on my 33mm tubulars, and the newer Donnely tubulars don't even have an inner-tube to pinch (it's a tubeless casing), so I would imagine they can be run extremely low and still not flat.