Trial and error is your friend. I finally found that 29 / 32 was about right, as the tyres got to 32 / 36 after warming up.

Track temp, rain, your weight, your riding style etc will all affect things, so best bet is to jot down start and finish figures (measure as soon as you come off the track) and note what feels good. I personally found they felt best when running at normal pressure once hot...
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