Unstable during braking carbotech xp10/xp8

MaysEffect

Tire pressures are very much dependent on alignment and weight balance. If you have more weight in the rear and additional negative camber i would keep the pressures the same front and rear no greater than 39psi hot

More camber and no additional weight - less pressure overall but less in the rear (this will induce a bit of understeer at first, drive accordingly)

Also like Hotrodz said, its dependent on tires too. More so the tread depth, design and sidewall profile.

Extremes or summer sports - higher cold pressures around 35-37psi.

Lower profile tires need less air for the same level of rigidity. Stock or larger profile tires require a bit more.

Also i personally don't recommend running low pressures under 30psi unless you know you will be putting a lot of force into them and have a stiff enough suspension to force pressure on to them like Rodz car.