I'm considering putting my (spare...) set of 20 rims - which are 9" rather than the "proper" 8.5" ones - on my S8 as winter wheels this year.
Am I right in thinking that these 9" rims would take the same size tyres as the 8.5" ones, which this page suggests, I think?:
http://www.audipages.com/upgrades/tiresizeoptions.html