I’m probably over-thinking this, but here goes. Like so many others, I’m considering a change in wheel size on my Cutlass. The stock setup is 14x7 SSI wheels with G78-14 tires (27” diameter, 8.5” width). At the front I’d like 17x7 wheels, staying close to the stock tire diameter and width (225/55-17). The question has to do with the offset of the wheel. The stock SSIs have 4.375” backspace – that works out to a +10mm offset. The 17x7s have 4” backspace and 0mm offset. That means the center of each wheel/tire will be shifted 10mm outboard of the stock location. That’s ok in terms of wheel well fitment, but I’m not sure what that does to the steering. I’ve done some searching on the internet and found that decreasing wheel offset can create (or enlarge) a positive scrub radius, which in turn affects the handling of the car. Apparently, a little positive scrub radius improves road feel in the steering, but too much can have bad consequences. Not knowing what the stock scrub radius is, my question is whether a 10mm (0.375”) increase in it would be significant or not. If anyone out there has knowledge about suspension and steering alignment, maybe you could help me understand this.
If you’re interested, here are a couple of articles I found that describe scrub radius:
http://www.hrsprings.com/technical/scrub_radius
http://www.miata.net/garage/offset.htm
Like I said, I’m probably over-thinking this. I could just order the new wheels with custom offsets to match the originals, but I’d like to know what other people have done in this situation.