AFS Cobra R Style Wheels purchased in November, 1999. 17x9 Front, 17x10.5 Rear. As is per usual for a first year type car, there were some fit-up problems with the Cobras, compared to a 99 GT. AFS had tried 315/35/17s on the rear of a GT and they fit fine, so they thought they would fit fine on a 99 Cobra. Not so. 285/40/17 is the largest. On the front, the 94-98 17x9 Cobra R wheels have a 24mm offset or 5.9" backspacing. The earlier versions use a 36mm offset, 6.4" backspacing wheel. Again, the assumption was that the 99 Cobra was the same as the GT and the 94-98 Cobras. Not quite right, but close. The IRS and the Front suspension are wider so the offset was increased on the 99 Cobra to 35mm or 5.625" backspace with the stock 17x8 Cobra wheels. This means using the 36mm offset older wheels would center the wheel just like the stock ones. But the 24mm wheels fit fine on the 99 Cobra even though the front is different than on the earlier Cobras and that is what I stayed with. See pictures below for clearances. The 10.5" wheels are tight on the inside on the 99 Cobra but work OK with the 285s. The rear wheels will need a spacer to fit tires larger than 285s.
Front Wheels--24mm offset, 255/45/17 tires
Rear Wheels--With 285 tires