So I am thinking of getting my 18" IROCS widened. Just dont know how wide.
They are currently 18x8 I'm thinking of going to 9.5 or 10.5. They are factory offset and I'm running a 4th gen rear. I dont want to do a lot of modifying to make them fit.

 

Won't stock offset iroc wheels with a fourth gen rear make the wheels stick out of the fender too much?

 

Yes they are just flush with the fenders. A little fender roll should fix that. I already have the wheels and love the way they look on my car. Which is why I want to get them wider.

 

Jack up car
use tape measure
widen wheel accordingly.

Should be ably to do 10 with little work, just some hammering. 10.5 and wider will work but with increasingly more modification

 

Lots of threads here about 17x11s on the rear, you going to 11 wouldn't be any different if you want to spend for 315/30R18s. Weldcraft can do it. On the front, there are a few examples here of 18x10.5s tucking nicely. You might consider 10.5s all around for now, as TireRack has 285/35R18s on sale, and DiscountTireDirect has some really cheap 275/35R18s. Then when your funds recover, I'd run 295/35s all around. With 18s, and an adjustable panhard, you shouldn't even need to remove the rear bumpstops for 11s, let alone 10.5s

 

11 can fit in rear with 295 and slight hammer to inner wheel well
Fatter tire more work to inner

Stick with a 9.5 and or 10 if you want to make it easy
Wider if you want to do more work

A 275 tire is ideal tire size for both

go for it running at least a 9.5 front wheel makes world of difference compared to a 8 wide wheel

When they widen they will most then likly add to inner portion of wheel

To measure front inner wheel lip usally ends up at the strut lip that sticks out a bit for a 18" wheel and is where your clearance issues will be
And inner wheel well for rear

 

As Zach said, try to go for 10" with a 275-35-18 tires, which you can buy any tire style or pattern (ultra popular size).

The widening is from the mounting flange inward, so make sure you can add the extra width there. Measure, measure, measure!

 

I always liked 275s on 10s, it always seems to look ok and handle very responsively, without endangering the sidewalls, if they find a nail while cornering or some such.
But right now 18x10.5s are cheap, and 275/35s are cheap, so I keep seeing it turn up, and I'm not hearing any problems reported. Besides, starting with wide wheels first lets you buy wider tires later, when your wallet recovers from the cost of the wheels.

 

Yup I think I am going with 10" I am going to get a quote from weldcraft for it. I am only looking to do the rears for now but may do the fronts as well in the future. I will try to measure it all out this weekend.

Ouch $235 a piece plus shipping. Oh well I'll probably still do it to have one of a kind 10" wide iroc wheels

 

Somebody has already done this with 18" iroc, not the first time.

235 and shipping is not bad. I paid 250 each when I had my wheels done but the place was local so no shipping