16's 17's or 18's (& winter tyres)

Thanks to contributions on here now the owner of a A3 S line quattro TDi 170 - just over two years old (sept 08)

Has 18" wheels with bridgestone potenza but want another set of wheels for winter tyres. Have read all sorts about caliper sizes etc, and trying to get info from Audi results in monetary units and not SI measurements.

So if you can help with dimensions for

a) PCD
b) offset (and is it +/-)
c) smallest appropriate wheel size

Wheels could likely be steel (better for all those potholes through winter) but alloys are possible. Not bothered about looks, car already covered in winter salt before noon on a Monday at the moment!

If anyone has recommendations for winter tyres would be interested to hear - michelin alpin will no doubt be ok and good value when costco discount comes around again, so likely to be my preferred, as they usually turn out to be a good tyre

thanks in anticipation of replies.

cheers


Darren

Nothing too fancy........have 5 spoke at the moment, so something similar would be fine, like the double clustered 5 spoke, but as i said, steel wheels black would do,

its the dims i'm really after so if you could help that would be great

thks