whats the biggest tire size i can put on my truck

[Kyer7]

hey can anyone help me out. I have a 2007 gmc sierra 1500 slte 5.3L. I installed a 2.5 inch leveling kit on my truck and I am wondering what size of tire I can fit on my truck. I am currently running 275/55R20 on stock gmc rims. whats the max height and width of tire I can fit on my truck.

 

thanks

 

[DwayneJ]

Are you prepared for the negative impact this will have on gearing?