Does anyone have an idea of how much tyre pressures should rise between cold and hot?

I have a rise between cold and hot from 22 to 22.5 front and 25 to 27.5 rear.

Does this sound reasonable?

The Xtreme wieghs 750kg and then has a significant amount of lard added when I get in

i'd say thats a couple fo psi high, i run mine about 18-20 psi and im 11 st

[Edited on 16/8/10 by omega0684]

I seem to remember reading somewhere about a certain percentage increase between cold and hot, but I can't find it now.

I guess the effect of the pressures being to high will make for less grip?

When I used to race, we took readings cold and set to the required pressure, did qualifying and as soon as we returned to the pits, checked again and let out some air to the cold "required" pressure. When they cooled they were lower than optimal. That way we knew that once hot during the race they would return to the right pressure.
Each circuit obviously made each tyre heat differently so extensive notes were kept for return visits.

My slicks were 16psi when hot, 12 when cold, Yoko o48's increased a couple of PSI.

Its spooky, makes you wonder about tin top tyres on hot day!

it does indeed, my tin-top fronts are supposed to be 36