[summitflier]

For a stock rear axle... anything with more than 4.5 inch backspace gets tricky.
Then it depends on your aspect ratio, the taller the tire, the more it bulges from the rim.

The front can be tricky too... if you pull the inner fenders, they will likely fit.
However a 6 plus inch backspace usually hits the tie rod ends when you turn too sharp.
The deeper the backspace, the less sharply you can turn.

Thats not to say it can't be done with a wider axle or wheel spacers on the rear.
I've also seen custom tie rod ends that were purposely "bent" to prevent hitting the rims.