I like your plan, Redscorts: 205s are likely a safe bet.
If I recall correctly, if you have a higher offset number (sorry, I can´t remember if this is technically referred to as positive or negative offset -- negative, I think), the point at which the hub meets the wheel will be further toward the outboard (or road-side) face of the wheel. That means that a higher offset number will move the wheel deeper into the wheel well, reducing the chance that the outboard edge of the tire will rub your fender but increasing the chance that the inboard edge of the tire will rub the strut. (Somebody correct me if I got that backward.)
As you point out, it´s possible to roll the fender lip if a wheel has too little offset. But if a wheel has too much offset, you´ll need spacers installed on the hub. (H&R makes them for the 2nd gen, though they´re listed as spacers for the Mazda 323; they´re not cheap but I wouldn´t buy cheap ones myself.)
Last fall I faced the same decision you do. I guesstimated using some crude measurements: With my stock wheel in place, I measured the amount of space between the existing tire and the strut and between the tire and the fender lip. (I used two scraps of wood as feelers and then measured the thickness of the two pieces of wood.) I then went to the tire manufacturer´s website to get the actual width of the tire I wanted to buy; that way I knew how much wider it was than my existing tire. That was enough to know how much of a rubbing risk the new tire itself would be if, hypothetically, my new wheel had the stock offset.
Of course the offset of the wheels I wanted to buy was different but I knew what it was -- 4 mm more. Having done the earlier measurement between my imaginary tire and the strut, it was easy to see that I still had 4mm of spare room between my imaginary tire and the strut. Though it was close, I was then fairly sure that the new tire would fit even with the new offset.
I had bought the wheels by that point but was still nervous about the tire rubbing the strut in hard cornering or when I hit bumps. So, non-risk-taker that I am, I brought the bare wheel to a garage and had them mount it on the car and compress the suspension. They confirmed that, even with the suspension bottomed out, there would be enough room for a 205 tire in the back.
I got my tires mounted on the new wheels just before snowfall. Because they weren´t broken in, I couldn´t test every possible scenario but everything seemed to work just fine. No rubbing on either side; no need for spacers or fender work. Phew!
- Rob
[ This message was edited by: Rob-from-Ottawa on 03-01-2003 13:16 ]
[ This message was edited by: Rob-from-Ottawa on 03-01-2003 13:17 ]