Has anyone tried using a 16x9 or 16x10 wheels with stock fd suspension in the rear? What offset or backspace would be needed?

 

The same offset as if you were running 17s or 18s, +50 or close to it.

Why wide 16s, BTW?

 

The only reason to run wider 16" is to run true racing slicks, as there are no properly-sized street tires available. And you don't need wider 16"s for drag tires either.

Actually, there are clearance issues with wide 16"s that are not present with 17 and 18" wheels. You will need aftermarket trailing arms for sure with anything over 16x9 and you might have other contact concerns.

 

I was thinking of running wider racing tires these season like 265's for autox in the rear.

 

Then you'll need to move up to 17 or 18" wheels to get properly sized tires.

 

kumhos are available in 265/45-16

 

Yeah, those will work. But I think you'd be much happier going to 17-18" wheels:

1. you won't have suspension clearance issues like you will with the wide 16" wheels.

2. you will have to get custom wheels for wide 16" -- a large number of manufacturers make "off-the-shelf" wide 17 and 18" wheels.

3. Kumho is the only manufacturer making tires in that size, and then only racing tires. Why limit yourself? A 265/40 17 or 265/35 18 size is available from several manufacturers in both street and racing tires.