GCN Says 15 Compression
If you hunt through the GCN videos you'll come upon one from last summer where a Tour De France team mechanic was quoted as saying their teams starting pressure goal was a 15% height compression. In theory on a near weightless bike, the contact patch would be a small dot. So bike and rider weight should set the tire pressure. I'm still not running my CONTINENTAL GRAND PRIX GP 4000 S2 28 MM /700C tires as low a pressure as the 15% test indicates but the lower I go the fast I go. I sweep a weekly ride of twenty with three out and back legs so I've have been using where I meet the leaders as my indicator. The lower pressure the lower the actual rolling resistance as the tire absorbs road vibrations that would normally consume power as the mass of the bike and rider is moved.