Stupid Question but....
 

I know we have 19" on our 2014 GT/CS Premium Convertible. Can anybody tell me the width? If we continue to use the stock wheel - which I really do like - what type tires would be recommended for DD/ (not in winter - just spring thru fall) for good cornering and grip. It has the stock Pirellis it came with. They only have 23 thousand on them so I am sure we won't have to buy any too soon but I am curious and doing research ahead of time.

I would like a wider tire in back but want one that will work with the wheels we have if we can - not sure how wide we can go? TIA

They are 8.5" wide. The standard has been go no wider than a 265 but Ford just put a 275/40/19 on the back and a 255/40 on the front of the 2015 50th anniversary car and it has 19X8.5" wheels. After looking at one at my dealer, you should be fine with a 275/40/19 on the back for sure and probably okay with them on all four corners. Hope this helps.

You're going to have a bit of rubber hanging over those GT/CS wheels with 275's. That's not the worst thing about those wheels - it's the offset. They're terribly tucked into the wheel well. Especially if you lower your car. Just a heads up.

Stupid Question but....
 

No, the 50th wheels are not the same as the 50th package wheels. The actual Limited Edition wheels are the same widths as the Performance Package wheels, 19x9 and 19x9.5, which is why they did the staggered tires.

For the OP's question, you could do a 265/40/19 all around, if such a size exists. Other than that, a 255/40/19 all around would be fine, which is the same size as the Track Pack tires. If you really wanted to do a 275, I couldn't recommend it, but I also don't think you'd have any issues. People have been putting 275/40/17s on Bullitt wheels for years (17x8 on the SN95 cars).

If you DO go the 275 route, do a 275/35 which will have less sidewall, and thus less bulge to worry about. You could do that size all around, or pair it with a 255/40 front, which would keep the diameters about the same.

I appreciate all the advice - tires are important and I certainly don't want to much bulge and ruin the sidewalls or have them wear improperly.

Our GT/CS has an 8.5 inch width. Last summer I put a 255 on the stock wheel and it looks good, not bulgy.

I wouldnt put a 275 on an 8.5, that is too much tire. If you are wanting to corner carve, a tire that is too wide will flex too much from what I understand. You might be able to get away with a 265, but I would check with your tire dealer to get their input. When I look on Tire Rack they say the minimum width for a 265 is a 9" wide wheel.