Jim, if you really want to go with the same size at each corner, then (according to my calculations and measurements) I think you can safely go with the 305/45R18 mounted on 18 x 9.5 with 6.5" backspacing. This should put the sidewall exactly in plumb with the outer edge of the fender.

This, of course, is based on information that I have from my truck - a 2WD. I can only assume dimensions and measurements are the same on your truck (hub placement within the fenderwell).

I think the front might rub, or more to the point, come into solid contact with the stabilizer bar on full turn.

 

that is what i am going to go with. now i just need to find the money.

 

oh yeah... once i get these on the truck i will somehow have to hold myself back a little and not do full TQ launches. i think i will dial in some 1.65's or so and then just chill there till i beef up my front diff.

with these tires and meth injection i could see some killer ET's on pump gas.

 

Do check the updates to my post.

 

The last thing I remember is you were looking for some different rubber for your factory rims!
Here's the thing...
Think about how empty life would be without all the smokeshows. 16" tires are cheap, even good ones.
Have you thought about throwing a set of Pirelli Scorpion Zero 275/50 R16's on it to see if they'll be good enough? They're not very expensive, have good dry traction, stiff sidewalls, and phenominal wet traction. Staying 16" would also keep the mass inward instead of farther out which will reduce performace.
I know you like the look of the factory rims. These tires are 29" tall and would probably look great on the factory 16x7" rims.

 

if i remember right he had some pirelli's and they were terrible on his truck. i could be wrong though.

 

i tired those exact tires but i think they were a 60 series. they did not hook at all. high 1.7's was the best i could do and with the stock tires i can pull lower 1.7's.

i would love to go with just a set of tires and save a butt load of cash but i dont know of any that will add traction. the only tire that is even close is the M&H 28" tall drag radial but they recomend it on a 9" rim. 28" tall is kinda short and a 7" rim would probably not work well either.

 

Hah.. you're right. They are 60s. Sorry they didn't work for you. I guess being shorter with less contact was just the wrong direction for your truck.

 

Did you say chill at 1.65 and NOT do full TQ launches?

 

If I could do it over again I would of had boyd make them 6.1/4 -3/8.

The 305/45-18 sit just a whee bit out but its only noticable at certian angles.
For most angle they sit flush.That is with a Step side bed.
Up front with the 6" Back Space, when the wheel is turned all the way I have a thick finger width between the inside edge of the rim and the Front Bumper side of the upper control arm. I wouldn't go much more than 6.5.

I have a 2wd though with 2' Hotchkis Springs.

Parish If you can wait-- I was planning on screwing around with My 4x4 GMC. I'm looking to throw some tires on that soon so while I had the stockers off I can throw the 18x9.5 up front to see how it looks. as far as back spacing is concerned.