Don't hit me too hard for this one, I searched and searched but couldn't find a thread discussing this exact scenario. I'm installing the Rough Country 1.75" spacers and 2" shackles to give myself a little more height from stock, and I'm planning on using a 31x10.5 tire on a 15x8 wheel.

Questions:
1. On a 15x8 wheel, is 4" backspacing acceptable? Will the tire stick out very far past the stock flares?

2. How much do I need to trim the fenders front and rear if I'm disconnecting my sway bars? I know that with the sways connected, there's just minor trimming on the rear and bumper cover trimming on the front. Haven't read about anyone doing this with the sways disconnected though. Trying to avoid going all out with trimming right now, just because I don't want to get involved, but I'll do it if I need to and put on bushwacker flares or something.

 

Bump! I think I answered #1 myself, 4" BS on a 15x8 is fine even with a 2" lift.

Second question still stands - with a 2" lift, how much trimming required with 31x10.5 tires on 4" BS, with the sways disconnected?

 

Might not be the exact answer you want but... when I purchased my 96 XJ the seller had already rolled the rear wells and cut the front. I lifted 3 inches and put on same size tire with zero offset, which is I think the same as 3.75 backspacing on that size wheel. I purchased used stock flares and was able to install them even though the wells were trimmed. They lined up exactly back at stock. I run disconnected and only get slight rubbing at the front edge of front flares only in full flex. So basically, if you consider my flares are at stock position, it's almost like my wells are not trimmed.


Hopefully in pics you can see the remaining flare on body to give you an idea.

 

I noticed after posting pics that you can see where the wells are trimmed. Basically the flare comes out then bends again. The flat part was trimmed off leaving the flare.

 

Yours will depend on how worn the springs and coils are to start with on what you will have to do. Then how quickly the shackles affect the leafs you have till they need to be replaced.