I had a different experience, my 4" steel amazon wheels were widened to 6" with the extra 2" on the outside at first, looked great and excellent roadholding, but the bumpsteer was too much, it was unpleasant to drive on uneven road surfaces and heavy. So I had them redone with more or less the extra width spread between the inside and outside which worked a lot better, lighter steering and the bump steer is very minimal. I found that the 3 Volvo factory options in the 60s for the offset on steel wheels were all different, depending on the use of the car, I suppose, rallying, road or racing.

Probably, the heavier steels wheels cause more bumpsteer than the lightweights ?
One day I will buy "Minilites" for my Amazon too. They look fantastic on it.

http://www.ccar.co.nz/amazon
Details about my wheels at the bottom of that page

Jim Hekker
New Zealand