Just curious why you didn't go 255/45-19's, as the overall diameter would be closer to your oem Pneros. According to Tire Rack, the Conti's are .7" less in diameter than the oem's. I think we can go up to 28" diameter on that rims without trouble. No ? OEM's are 27.7".

Please post a straight side on pic, if possible.

 

There are not many tire choices in the 255/45/19 size and they are all expensive! I have the same rims but will wait to wear out my Nero's to make a tire size decision...

 

I went 255/40 19 (instead of 255/45 19) because I wanted a wider tire with lower profile - for better handling. Also, it's the identical wheel/tire size as the V6PP, and those look great. It's very close to the Brembo set-up, just .5 inch narrower wheel. I also worked closely with the tire manager at my Ford dealer, and this was the best set-up. Ford simply re-calibrated the speedo for the new tire size, when they did the install, at no charge. I can't tell you how many Mustang owners ask me about the tires, and love how they look. Oh, and also, they are several pounds lighter than the OEM tires - helps reduce unsprung weight. I suggest you do NOT go 255/45 19, but go with 255/40 19. Otherwise stick with the stock size, 245/45 19.
Picture of front:


Picture of rear:

 

PJR

Thanks for the pics. Interesting decision. I would actually prefer the tire fill the wheel well better, and have a "boxier" stance at the contact area. IMHO, the oem Brembo setup leaves too much wheel well visible. A 255/45 19 is still within plus-size specs.

Can you elaborate as to the recomendation against 255/45-19's?

 

Hi, sure. The '45' part of the tire is called the "sidewall aspect ratio". The larger that number, the larger the sidewall. The larger the sidewall, the more you increase comfort but descrease performance. So '40' will give you a more agressive stance and contact patch, more so than '45'. Plus, the tire manager at Ford preferred 255/40 19 to 255/45 19 (so do I). Plus, the V-6 Performance Package runs 8.5 x 19 wheels, with 255/40 19 summer rubber. So I did the same. The look is WAY better than the stock Pirellis, and the cornering grip is greatly improved. As far as 'fill the wheel well better', I do not notice the difference (it's about .5" less diameter overall). And the way to really 'fill the wheel well better' is to lower the car and put on wider rims with bigger rubber. I'm not going to do that because I love the 19" nickel wheels, and they are so rare, I almost never see them on other GTs at the shows I go to. Hope that helps, let me know if you need any more info.

 

Okay, I can see that rational. But using that rational (not including the appearance preferences stated), and staying with the OEM 45 series tire, going one plus size to 255's, I would guess there would be inperceptible differences for on-street driving. True ?? My goal is not to necessarliy increase tire performance, just not affect it adversely.

 

Correct, simply bumping up to a 255/45/19 wouldn't be too noticeable once the tire's broke in, 0.4" taller overall, raising the car only by 0.2". Your speedometer would read about 1mph off, and the extra tire width would give you wheel rim a little extra protection from the extra width on the sidewall.

The 255/40/19 option was simply done to increase handling performance through steering response of the shorter sidewall, and to force the tire to sit more flat/square on the road for a slightly better contact patch.

 

How did the 40 series effect the ride quality compared to the stock 45? I ask because I need a balance between performance in the corners and comfort while traveling, and would consider staying with the 45 series when the stockers wear out, but I would like a bit wider tire too...At least I have a while to make up my mind!

 

I use my GT as my daily driver. I do not notice any decrease in comfort - part of that is due to the Contis...which got great reviews on comfort and low road noise. I will use this size again and again with my set-up, 255/40 19.