I whack em up to 100 psi whatever they are…. must be a legacy of riding rock hard 18mm tyres in my youth
I run them all (various flavours of 25mm - currently riding GP 4 Seasons the most) at 120 psi, through some weird fear of pinch flats. ![Undecided :-\](/forum/Smileys/classic/undecided.gif)
I used to do that, until I realised that the gauge on the pump I was using was chronically under-reading and what I thought was 100PSI was more like 75-80. 100 actual PSI turned out to be pointlessly skiddy on the Streetmachine (40mm Marathons), but somewhat better rolling on the Dawes (28mm Marathons, gets used for hauling a lot of stuff). I didn't have the Brompton at that point, but 80PSI on the back would noticeably up the treacle factor.
So I invested in a reliable gauge, did a bit of trial and error, and arrived at pressures that seem to work well for each bike.
I've only had a pinch flat when a regular puncture has sneakily robbed the tube of pressure before I've noticed... Even on the mountain bike at 30PSI (though I've yet to do much in the way of rocky stuff on it). Barakta managed a spectacular one on the trike once, by landing the rear wheel squarely onto a nasty pothole at 30mph - in that instance we were mostly pleased that the rear mech was undamaged.