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Maximum Tire Width for GT500 with SVTPP


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With people starting to foray beyond their stock SVTPP wheels and tires and Ford SVT being tight-lipped on the matter, I'd appreciate knowing if anybody has determined just how wide a tire the 2011 GT500 can accommodate (front and rear) and whether or not the SVTPP suspension (or any of the most common aftermarket suspension modifications) are likely to hinder tire width further.


Working from the factory configuration, the rear tires are 285mm wide and 28" in diameter and the front tires are 265mm wide and 27 1/3". Both wheels are 9.5" wide with a +45mm offset. Since everything is also offset-dependent, and one could theoretically mount ever-wider tires upon wheels with a large enough offset, let's presume +45mm to be a constant.


Taking half of each wheel width and deducting the positive offset, the rear can accommodate wheels that extend 97mm inward from the mount. The front can accommodate 87mm - presuming my logic and math are correct.



This leaves me with 3 fundamental questions:


1. How much wider can I go, particularly with the rear tires? Since SVT won't offer anything official, has anybody configured their own vehicles with wheels and tires that extend farther inward using comparable diameters? If so, by how much?


2. How much taller than the factory diameters can the tires be presuming equivalent width without inviting the risk of rubbing on the chassis or other suspension components?


3. How much of a variance from the factory diameter is significant in terms of the PCM? (i..e what could I "get away with" in terms of using the existing PCM programming and dealing with the fact that the speedometer may be 1 or 2 mph fast or slow?


In considering the Ford Racing look-alike 19" wheels for the rear, they come with a larger offset to compensate for their wider (10") width. Doing the math, this should allow them to accommodate an additional 10mm of width (295's), but the closest size (295/40-19) would result in a diameter of 28 1/4" rather than being just shy of 28", or almost 11" taller. How much of a problem would this be likely to be, both physically and according to the PCM?



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