Did you just get a Focus RS or have one on the way? Depending on how you've configured your RS, you probably have 19x8 ET 50 dark grey cast alloy wheels on 235/35R19 Michelin Pilot Super Sports. For many RS drivers there is no need to upgrade. The Michelin Pilot Super Sport is a great match for those looking for a balanced tire. It's got a crisp steering response, good dry grip and very good wet grip. The tire also provides a quiet drive and rides well for its category with decent wear. If you want even more grip and better responsiveness for a second set of wheels and tires that will be used equally for both autocross and track days, take a look at 235/35R19 Bridgestone Potenza RE-71R mounted on a set of lightweight wheels.
Which wheel should you look at? Your original wheels are eight inches wide width with a 50 mm offset. Since we don't sell the Original Equipment wheels we don't have exact weights, however anecdotal feedback from other RS drivers says your standard wheels weigh approximately 28 lbs. and the optional forged wheels weigh 26 lbs. Both the standard Michelin Pilot Super Sports and the optional Michelin Pilot Sport Cup 2 weigh 22 lbs. Ideally we'd want a wider, lighter wheel that's relatively close to our 50 mm factory wheel offset. The 20 lbs. 8.5" wide 45 mm offset Advanti DST Hy Hybris meets the criteria.
Now you can have even more fun in your RS!