So I went wheeling this weekend and learned that the rubbing when I turn hard wasn't in fact rubbing on the fenders, but the back of the tires are actually rubbing on the LCAs!

Is this pretty common? Whats an easy fix? I think im only running 31X10.5's

 

I am guessing your running the stock rims in your pics. If so its the BS of the wheel. I was running those rims with 30x9.5 tires and rubbed at full lock. You could get spacers or some rims with less BS.

 

Tkdtim
Take a close look at your turning knuckle, there is a bolt that has a nut on it, that acts as a steering stop. You can pull that bolt out , and add a few washers to it. It will take some trial and error to find out how many washers you need. This will decrease how sharp you can turn by a tiny fraction, but you will stop rubbing your LCA's.
Personnaly I don't like spacers behind the rims, as they change the suspension geometry. Your other option is a set of rims with less backspacing.