hey guys just got the Old Man Emu kit. Now its time for winter and it dose get very cold here. - 20 c - 25 c. I'm thinking 245 70 15, 255 70 15, 265 75 15. Im running 235 75 15 cooper LT. plus I have some Gateway Gombo mudders with a size that only says 12/15 12 wide 15 rim do any of you now how to tell how to size that. bias ply