Help - Max Size Tire For Gs400 With 20" Rims

[LexusWoman]

I recently purchased a 99 GS400 with L-Sportline 20" Rims and suspension kit (2" lower I think). Tires are worn adn I am ready to buy new tires....preferably not Pirelli. Currently Front is 245-35-20 and Rear is 275-30-20 which is recommended by L-Sportline. My concern is that the actual tire diameter of Michelin tire (same size) is 1" greater than pirelli....so my quesiton is what is the MAX Diameter/Width that will fit so I can shop around adn see what will work.

Thanks