I have 19"x11" iforged wheels with 295/30/19 tires on the rear.
iForged wheels do not reveal the offsets, so I am wondering if anyone can tell me if i can fit 305/30/19 tires on my 996 C2 without rubbing issues.

Currently no rubbing issues with the 295/30's. The car is slightly lowered on PSS9s.

Also, if i go wider in the rear, do i have to also go wider up front?

 

Your best bet is to take one of the rear tires off and measure the offset. I just had to do this yesterday.

Calculating the offset of a wheel is a fairly easy mathematical equation. First, measure the overall width of the wheel (remember, just because a wheel is 18x7.5, does not mean that the OVERALL width is 7.5”. It means that the measurement from outboard flange to the inboard flange is 7.5”). Next, divide that width of the wheel by two; this will give you the centerline of the wheel.

Overall width/2 = Centerline

After determining the centerline, measure from the mounting pad to the edge of the inboard flange (if the wheel were laying flat on the ground – face up – your measurement would be from the ground to the mounting pad). This is your back spacing.

Centerline – Back Spacing = Offset in Inches

Inches x 25.4 = Offset in mm

Then get on the phone and call the guys at Wheel Enhancements in Culver City. They really know their stuff and will make sure you don't go down the wrong path.

 

I have 11" with 315/25 on a C4S

 

You are running too tall as it is....

You should be running a 305/25/19 you could also use a 315/25/19... You're running 997 tall tires....

-Eli