i have 15" mickey thompson classic II rims with like 3.5 in back spacing with 33x12.5 in tires...if i wanted to put some 1.5in spacers on to widen my stance a little bit would it cause any problems?

 

That would make your total back spacing 2" ....Your ball joints may wear out quickly due to the added stress....If you take that route replacing the Ball joints might be a routine chore and you will also have to look into reinforcing your axles with some welded gussets...How wide are your rims? Are they 8"? Maybe you should look at getting a 10" rim or more that would give you the wider stance you are looking for, but still maintaining the 3"-3.5" backspacing...Give it some time and others will chime in...

 

they are already 10" i want more tire sticking out past the flares for look and stability but dont want it to cause problems down the road

 

I'm sure there is a reason why I've never seen a wheel with less than 3.75" of backspacing.

 

You want to run 2" of backspacing on a 10" wheel?

You are shifting your offset from strong positive to a very strong negative value.
This is not advisable for durability of your axle bearings and joints.

 

that would be a lot of backspacing, and I'm not sure it would look that great unless your running a huge lift and tires.