Running at 40 psi cold will be near 46-47 psi when hot and you will be driving on the centres of the tyre and less rubber on the tarmac, hence less grip and turn in feel. 36psi is more than enough in the tyre for the weight of the car. The point of xl tyres is so you need less pressure rather than more. Id reduce the pressures in your tyres and the grip will increase as you have more tyre touching the tarmac.
