I think it depends slightly on the brand of tire, but I set the cold pressure on Dunlop 208GP's around 28 front / 29 rear and then check them immediately after exiting the track. Depending on the ambient temps, I would expect to see about 3 psi gain or maybe a bit more if it's hot out. If you do do a trackday there will most likely be a tire vendor on site and you might ask them or one of the instructors. Walk the pits and see who's running your tire and ask those guys as well. Anyone else?