Finally some new tires!

[cleveland48]

Hey guys finally got me some new tires, the are Cooper at3 285/70/17. So far no rub going from lock to lock, but I'm gonna take it off road this afternoon to no for sure. I removed my mudflaps before the install. Now here is my ? Going by my GPS with factory tires my speedo was 1mph fast with 285's my speedo is mph slow. This is at 70 mph. Theses tires are 3.5 % larger than factory tires according to tire calculator. So when I try to check my mpg I will multiply trip by 1.035 correct? I'm just checking since my speedo was off from the factory anyways. Does this sound like the best way to check current mpg still? Thanks for any help guys.
Will try to do some pics soon

 

[cleveland48]

I flexed it good in some ruts today turning lock to lock and backing up lock to lock and zero rub. I very happy needless to say, and very curious. I know all vehicles are different but I was prepared to to some trimming, and possibly chop body mounts. Sorry crappy phone picks.