The widest tire that you can safely mount is going to be very different from the widest functional tire for an 8.5" wheel. Sidewall support is very important. To give you the best recommendation, we need some context in regards to how you plan to enjoy your Mustang? Are you cruising around town, drag racing light to light, going out for canyon runs or doing any track days?this is probably some where on here, what is the widest tire I can put on the 19 by 8.5 GT rim? thanks in advance;
You don't really gain much by putting any wider of a tire on that wheel, so my recommendation would be to leave it. I would highly encourage a wider (and lighter) wheel setup. 18x9.5" front with a 255 or 275, and then 18x11" or 19x11" with a 305 tire. This would provide a big increase in traction, and when you have a lot of power, traction = fun.Thank you for that Ryan. I would appreciate any help on a suggestion if you could?
I have the stock 8.5x18's on my '17 GT. I only do normal daily driving, and the occasional 1/4 mile runs. I currently have Nitto NT05's in the stock 255 width out back. I had been thinking about a 275 width to save from having to change wheels so that I could go bigger. A 275 most likely will still not be enough tire (Whipple 2.9/Auto Car), but not really looking for max effort grip wise either.