What wheel backspacing do you recommend and where does that leave the tire setting in comparison to the fender? Thanks

2013 JKU
RK 2.5 Max Travel
35X12.50X18
18X9 Wheel

 

Stock Rims are typically 7.5" wide with a 6.25" backspace. Stock tires are 10"

When going up to bigger wider tires you want 4.5 to 4.75" back spacing.

So If I did the math correctly your 12.5" wide tires with 9" rims that have a back space of 4.5" will move 3.75" further out than stock.

 

Maybe a look at my web page helps a little :-)

http://www.sor7.com/JEEP-Tires.html

 

The most common setup is a 9 inch wide wheel with 4.5 inches of backspacing. Here's what it looks like with a 12.50 inch wide ttire.

 

I have 18x9 Level 8 Trackers and they have 5" of backspace. They work perfectly with no rubbing anywere...lots of clearance. They actually stick out of the stock fenders a lot more than I was anticipating... I think 5" gives a nice stance...