TRYING TO FIND THE RIGHT GEAR RATIO FOR MY BIKE

WELL IT IS TIME TO FIX MY BIKE I AM TRYING TO FIND OUT A GOOD GEAR RATIO FOR MY BIKE
AS IT STAND I AM RUNNING A 36T FRONT 18T REAR WITH 1.50 REAR TIRE BUT I WANT TO PUT BIGGER TIRES ( 2.25 tires) SO HEAR IS WANT I AM TRYING TO FIND FIRST I GOT A 35T MILWAUKEE BASH GAURD I WILL BE PUTTING ON WHAT I WANT TO KNOW IS HOW DO I FIND THE SAME GEAR RATIO I AM RUNNING NOW WITH BIGGER TIRES IS THAT POSSABLE

ROBBIE IS ON HIS GAME BOARDZ