I have 19x8.5 40mm offset wrapped in 235 35zr 19's dont know what size spacers I need for the rear. Its a tossup between 15mm-20mm at 20mm will I need to roll the fenders with an s tech drop? anyone with experience on this please chime in. TIA

 

Although I can't provide a response with experience at this point, I did go through the wheel & tire specs thread to see what contributors had run successfully. My conclusion was that a 19" x 8.5" wheel can safely range between 30mm - 45mm positive offset. You probably still have room for a conservative spacer.

I would suggest a search for the spacer terms you're looking for. "20mm" should work for starters. I think most results should pertain to wheel spacers.

The wheel and tire spec thread should help as well. Contributers specify if they used spacers and the size used.

 

go for the 20, i got 19 x 8.5 with a 35mm offset and i just put 15mm spacers for the rear and about to put 5mm in the front.

 

I wouldn't go over 15mm in the rear. Even with a recentered rear beam, 15mm spacers on 18x8 with a 35+ offset it rubs on the big dips. You should be fine with 15mm since you have alittle more strech to your tires than my 245s on an 8" rim.