I am currently stationed in Iraq and I had my wife purchase a white 1999 Mustang Cobra convertible for me. Anyway I was looking at putting 315/35/17 tires on the back with 10.5" Bullit style wheels from American Muscle. Their site says they will not fit the 99+ Cobra with IRS. I have read here that if the IRS mount bolt is ground down or replaced with the button head one this tire size will fit. I would like to know for sure these will work before I spend the $$$ on them. The Goodyear F1 tires I am looking at are about $300 each so I don't really want to waste the money.
Looks like I may have found my answer per the American Muscle web site:
Why can’t I put a 17x10.5” rim on the rear of my 99+ Cobra? The 99+ Cobras have an Independent Rear Suspension (IRS). Using a larger wheel means that the tire’s sidewall will rub the rear IRS subframe-mounting bolt. However, by changing out the stock .5” factory IRS subframe bolt with a shorter one, you can use 17x10.5” rims.
Thanks for the link. I will check out the site to see what you have available. Right now I am just doing my research. I mention the American Muscle wheels because so far they are the only ones I saw that recommended a 315 tire, but they said would not fit my Cobra. My tires are not ready to be replaced and with me currently in Iraq, I will not be burning them off any time soon. I like the staggered look of the wider tires in the back and want as big of tire as I can fit in the back. I don't want larger than an 18" wheel though. I like what is commonly called the "Bullet" wheel because they remind me of the classic American Racing Torque Thrust wheels from the 60's-70's. I also like some of the Saleen style and 03 Cobra style wheels, and want to keep the cost down as much as possible since the Goodyear F1 GS D3s in these sizes are not cheap.
Sorry, but after racing dirt tracks for 5 years and having many performance cars over the years, I couldn't put Sumitomo's on a Cobra. I haven't heard anything really bad about them, but I prefer a tire that I know has great performance. I have experience with the Goodyear F1 GS D3s on a previous car and am still looking into others. So far the tire brands I would consider are Goodyear, BFG, Pirelli, Yokohama, and maybe Nitto and Falken. I have had all of the above tires except the Nittos at one time or another on a car or motorcycle. I haven't had any experience with Toyos myself but have heard good things and would consider them as well. I want to get maximum traction while still being decent in the rain.
I am now also looking into 18"s so I can put the Wilwood 14" 6 piston front brake kit on the car.
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American Muscle wheels - 
