I have a 1999 XJ with the "Wheel Part Number: #9009" wheels shown on http://www.originalwheels.com/jeep-w...ee1996rims.php and 31x10.5R15 tires. I'd like to replace these with some cheap steel wheels but I'm not sure which backspacing I should look for to keep as close to stock as possible.

These are some of the wheels I was considering:
http://www.jegs.com/i/Rugged-Ridge/4...873+4294829736
http://www.jegs.com/i/JEGS-Performan...81010/10002/-1
http://www.roughcountry.com/black-da...-bw158545.html

I believe I need 15x8 rather than 15x10 for my 31" tires, but I'm not too sure which back spacing I should look for. Any advice is appreciated!

My setup: 15x8" rim w/ 4" of backspacing with 33x12.5" tires. This is a very common setup on the XJs. I have minimal rub of the tire on the LCAs at full turn of the steering. The tires stick out past the flare 3.5", the legal limit in VA is 4" so I'm good. If you use the same rims w/ 31x10.5s your tires will hang out 2.5" past the flare. IIRC the stock backspacing is typically 5.25", so if you put a 31x10.5 on a 8" wide rim you will have 1.25" of tire hanging out past the flare. These measurements are all on the front axle, the rear axle is slightly narrower so they will be tucked in just a little more.

Depending on the law there, I would suggest a 15x8 w/ 4" of backspacing. That will leave room for stepping up to bigger tires at a later date if you desire. A 31x10.5 can safely go on a 15x7 wheel, but a 12.5" wide tire can not. A 10.5" wide tire can go on a wheel with 5.25" of backspacing with minimal rubbing on LCAs, but a 12.5" wide tire will not.

x2

15x8~4 inch backspace would be ideal for you (you may even go 4.25, but wider tires will rub)

I thought 15x8 with 3.75" BS is the setup. I'm goin with a 32x11.50 tire but you know the drill...it'll be 33x12.50 soon.

We're talking about a 1/4". This is one of those things like horseshoes and hand grenades. Close enough. I went with 4" of BS because that's what the Cragar Soft 8s come in. They are cheap and proven, so I use them. That 1/4" would help with the tire rubbing the LCAs, but the turning radius is still great though slightly reduced.

ideally, yeah, 15x8 with 3.75 for anyone with 12.5 wide tires that want that aggressive stance.
but the op wanted to keep it looking stock, without sticking out past the flares, so with a 10.5 tire, 4 to 4.25 would be ideal for him.

Thank you all for the input. I'm just looking for some basic black steel wheels. Does anyone have specific recommendations with 4 or 4.25" backspacing? A few of the ones I linked were at 4" but I'm happy to consider other ones as well.

When moving from P235 to 31"x10.5 tires, with stock rims, 3" lift, I was rubbing the LCA at full turn, 1.25 thickness Spydertracs wheel spacers, never problem with the spacers, 400+KKm and many many years, always torque to 100 ftlb.
No rub still when onto 33's at 5" lift.

go with the 4"

the higher the number, the closer to the control arms and will rub.

If you want cheap wheels check out Summit and Jegs both have cheaper steel wheels in a 15x8" with 3.75-4" of BS.

hey man where ya been!?

SAY,Fred!

I thought the higher the backspace value, the closer the inner edge of the wheel is to the vehicle. How could 4" vs. 3.75" backspacing help with tire rubbing on the LCAs? Maybe I'm missing something, so I look forward to your reply. PS. I have 15x8" with 3.75" bs and 4" lift, and I get rub sometimes with the sway bar disconnected.

yeah, a 4 inch bs will be closer to the frame, whereas 3.75 gets that wheel mounting surface further away towards the outside of the vehicle.
i run 15x8 with 3.75 on most of my jeeps, and 15x10 with 3.0 on my main wheeler. i've also added 2 inch spacers just to test them out. the wheels are aero beadlocks wrapped in 36x13.5 bias iroks. no rubbing even at full flex, but fenders are cut to clear. sway bar is rarely connected.