Wheel Offset
 

A while back I posted that I was having issues with tracking/wandering in my Z06. Got a good alignment and posted back that it was fixed. The drive home was on good highway at normal highway speeds. Well, now I've had a chance to get out and play a little on the not so good roads around home at some "higher speeds." While tracking/wandering is not nearly as bad as it was before alignment, it still gets pretty bad a higher speeds. Let's just say 80 or above, car becomes quite unpredictable, especially passing someone where I have to cross the crown of the center line. The car has aftermarket wheels that were on it when I bought it. Prior owner upped the sizes to 18/19 from stock 17/18, but the offsets are quite different now. Can changing offset relationships affect handling???? Stock front is 17x9.5 with 54 offset, now I have 18X9.5 with 53 offset. Not a big change in front. Rear: stock 18X10.5 with 58 offset, now I have 19X11 with 73 offset. Quite a change in rear. So front offset decreased 1 mm, rear offset (per wheel) increased by 15 mm. Does anyone believe this could affect handling? If so, could a spacer be used in the rear to get the centerline of the wheel closer to where GM intended it to be?

Or is all this not relevant and I need to look for something else? By the way, I know it needs new tires, plenty of tread but tires are 7 years old by date code, and that may be the problem, but if I have the wrong wheels on the car, I don't want to buy tires if I am going to have to get different wheels. Everything in the suspension has either been replaced or confirmed within specs.

Thanks in advance!

The offset is not relevant. Your problem lies elsewhere.

Oops, meant to post this in tech.

You need to have the caster increased in your alignment settings.