i would like to know if i will have a problom running 18.9 backspacing is 4.5

 

Should be fine with 4.5bp. Anymore than that you may run into rubbing.

 

thats good i couldnt find rims with any better back spacing then that

 

You will be fine with 4.5" BS. I run 33x12.50R17 Cooper STT's on a 17x8 rim and no rubbing lock to lock steering....even when I was stock suspension. Only thing I rubbed was the rear fender flares with stock suspension as the tires stuck out about 1/2" outside the stock flares.

With a 2" lift this solved the rubbing issue!

 

so what rubs when not having the right size

 

If you have a bigger BS than 5" and you plan on getting 11.5" or wider tire you will require spacers so you avoid rubbing lock to lock steering.

If you get to small of a BS with a wider tire....you will rub on your Stock Fender Flares when you off-road and flex hard due to them sticking out beyond the stock flares. This is when you will need a lift or wider fender flares.

 

okay good to know so i think i should be okay