Hi, I'm that guy from New Zealand and initially made the mistake by having the extra width on the outside of the wheels, that caused a lot of bumpsteer on uneven roads, (no problem on smooth surfaces) so I had them all changed to an offset of 20mm (1 1/4")and its fine now. First the offset was zero. Original 4" wheels had 1" offset.

The rims used were new, only the wheel centres were used. I know that some workshops actually cut the rims and weld another 2" extra rim in between, whichever way you do it, specialist equipment is required to get it right. The best advice is not to change the Offset too much from standard specifications, I think. In other words, when widening the rims, make sure that the extra width is going to be split evenly on the inside and outside of the wheels mounting area. (for normal road use that is)

Below is a link to a diagram to show you what backspace and offset are, there is a lot of confusion about this terminology. Backspace depends on the rim construction, but offset is more defined. Backspace should only be used to for clearance purposes.

I found that in the 60s wider rims for 122S were available with different offsets, I suppose for different use, rally, race or road.

Jim Hekker
New Zealand
volvoadventures.com