I've fitted CKII's (19's) to my S3 Sportback.
ET44
H&R Springs
Orginally went with 225/35/19 Falken FK452's but they rubbed
to say it a little louder19" x 8J + ET44 and 225/35 profile tyres will rub on an S3 Sportback
Hopefully me repeating this will save others the head ache I had in changing my tyres over and then selling the 225's and being £170 down for the pleasure
With the 3 dr you can get away with 225/35/19's 19 x 8J on an ET44 on H&R's (as per Decked's above) without an issue. Maybe even 235's depending on tyre selection (as per Boydie's)
Regarding performance - obviously the ride is harsher slightly - but I noticed this more when going from standard to H&R springs, than when I went to the 19's, its noticable slightly.
I didnt notice any difference when going from 225 down to 215's for everyday driving - I suppose under the full right boot it will be noticable but I havent noticed it yet.
I drive quickly on a blast out maybe 10% of the time so for the other 90% my car looks 100% better and doesnt rub its tits in. So 215's was an easy decision for me.
I'll add some pics tomorrow if I get chance of mine on the 215's now, but seems this is a BBS thread it'd be a shame not to add some pics of them in 225 guise.