Re: 146 ti 1998 wheels offset
The original offset for the ti is 38 afaik.
The smaller the offset the more the wheels protrude out of the wheel arches, i.e. you get a wider track from smaller offset.
Another thing to consider is that any wheel you buy is likely to have a 7 inch rim and this will also cause the wheels to protrude more than the standard rim(by about 1.5 cm I think).
I put my 155 wheels on the ti and with the smaller offset and wider rim they actually rub at the front while cornering (15 inch wheels!!)