In Reply to: You can use 15mm spacer to widen the track... posted by Jon on January 09, 2002 at 15:26:58:
If you put 15mm spacers on the stock 15x7 wheels, the outside edges of the wheels are still about 5mm inside of 17x8ET23 wheels.
I've seen cars with this setup and it does look quite a bit better, IMO, with the wheels farther out.
Rear rims in 7.5 to 8.5 width mounted with 225 or 235 tire section should have an offset of approximately 20mm.
Nowadays, there is a wide selection of rims coming from the e36 range. Only problem is that those wheels come with a 35mm offset. The spacers that everyone talks about are added to the wheels so that it reduces the offset (35-15=20). Spacers are used to adapt a rim that otherwise would not fit, and not necessarely to widen the track as is the habit with Porsche 911s.