I dunno, I've been running G1 "38" (40mm) for cumulatively thousands of miles without issue. I ran the 35mm before that and also had no issues. The 40mm were wonderful at Iron Cross race a couple weeks ago. For racing I run them at 32/28psi (F/R) -- I weigh ~175lbs; this feels about right, so this is lower than some other reports here, but 40psi seems like it should work just fine. I am using them now with narrower DT R460db rims, but previously was with Grail rims. These are definitely my go-to tires when I want something sturdier than the Compass Barlow Pass tires -- e.g. for racing.