17's are definitely the way to go for track use.

While square setup may have some advantages, it can also put you in a car class where you are less competitive. Things like tire size do effect what class you run in

Well I just got a set of 996 Lt Alloy Carrera wheels for pretty cheap and they're being refinished. I'm going to use them for my track wheels for now. Since I'm not wearing the outer edges of my tires yet, my shop didn't want to try setting my car up with more negative camber. Maybe once I get faster and start wearing tires on they outside edge instead of evenly they said.

Do the 17 x 8.5 rears fit on the front with 255/40 tires if the car still has factory springs rather than coilovers? If they do, I'll keep an eye out for a pair of rear Boxster S II wheels since I already have a set of those.

Update
 

So I ended up getting the Yokohama Advan A052's. With the 8 inch front rims up front and the 10 inch rims in back with 20mm spacers, they come out a touch more and look sharp! I had the wheels checked for trueness and refinished with metallic silver powder coating. Tomorrow I'm headed up to Watkins Glen for a 3 day HPDE. It will be fun to try them out!

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Nice! They should be beyond amazing on the first lap but fall off pretty hard after that. Let us know how they hold up after 3 days. Watch your shoulder wear as they typically like a lot of camber which you don't appear to have.

+1

Let us know how it goes on the Advans. I'm curious how it performs with the spacers; I recently removed mine for safety as I discovered a wheel shimmy at around 60MPH-70MPH.

Paul, your wheels came out pretty nice! I would 'like to suggest' installing the center caps it will make the wheels stand out better..

There is a guy on Rennlist that offers (non OEM..) center cap sets for about $50 bucks and they look pretty good (I got a set for a friend of mine's 997 and they look great IMHO, specially for the cost..

The 20mm spacers on the rear put these 996 wheels where they need to be on a 986. I drove 40 miles home yesterday from the shop on the highway and they don't shimmy at all. My preference would have been for a wheel that didn't require a spacer, but these wheels were too good of a deal to pass up!

Yeah, right now I'm on the stock alignment settings for the ROW M030 suspension. I've been on Michelin Pilot Sport 4S tires with no shoulder wear, we'll see how these do. I hope they feel good for more than 1 lap!

Thanks Gilles, I've got center caps, including a set of Fred's (Nine8Six) faux centerlock caps. I've left them off for now as I'm headed to the track!