I'm having a set of wheels built for my 2016 991 GTS and I'm trying to decide exactly what size I want. The GTS setup is 8.5 x 20 ET51 with 245/35 ZR 20 and 11 x 20 ET52 with 305/30 ZR 20. The GT3 RS has a lot more rubber - 9.5 x 20 ET50 with 265/35 ZR 20 and 12.5 x 21 ET48 with 325/30 ZR 21. I can go for the 20" diameter in the back too, but the 21" really intrigues me.

This is for track use and I'll be using Pilot Sport Cup 2s. Does anybody know how this setup would work on the GTS? Is the geometry of suspension and body similar enough not to cause rubbing?

Thanks

 

Anybody?

In the absence of any responses, I'm pulling the trigger tomorrow on the 265/35 ZR 20s and 325/30 ZR 20s. 21" in the rear, while they may look awesome I believe they would be robbing the car of some torque (5% - too much) and that just doesn't fly. I was hoping somebody had some direct experience, since the above is conjecture, but it makes sense, doesn't it?

 

IMO, Your GTS is set up for best handling from "it's" suspension as the GT3 achieves its level with "its" own. Are 21's offered as an option on the GTS. The answer may ALSO be in the offset of wheels...may point to difference in width of rear track of each car which may change dynamics of GTS... Would tire diameters be affected? I'm just saying...

 

IMO, Your GTS is set up for best handling from "it's" suspension as the GT3 achieves its level with "its" own. Are 21's offered as an option on the GTS. The answer may ALSO be in the offset of wheels...may point to difference in width of rear track of each car which may change dynamics of GTS... Would tire diameters be affected? I'm just saying...

 

I've abandoned the 21" idea - you're right that it would probably be messing with the suspension. Though I believe the GT3 RS, GT3 and GTS suspensions are pretty similar and the GTS would probably run ok with the larger diameters, there's the reduction in torque that finally made up my mind for me.

I'm maintaining the stock offset on the wheels and thus the stock track, but I've also ordered 5mm factory spacers. Widening the track or the effective rubber patch is unlikely to have any effect but increased grip, cornering, etc. We'll see.

Frankly, after only a few days with the car I can see no room for improvement - it's an incredible performer on the street and highway and I can't wait to get out on the track (2/20 - PCA instructor training at Thunderhill.) It's on the track that I expect to see some advantage of wider rubber, thought the new wheels and tires won't be here in time for this first event. Probably better to take it easy anyway.

Thanks

 

I personally like the idea of 20/21's & plan on doing so sometime as well...but not as track set-up.