Hi All:
Since this is an HPDE tire thread, I figured I throw out a tire/wheel issue I've been struggling with for about a year and half. I'll set the seen for my 2017 GT Performance Pack's suspension which is stock except for the following: Vorshlag Custom Spec Offset ForgeStar F-14 wheels, 11" x 19 all four corners, Vorshlag Camber Plates, I also enlarged strut tower openings with their cutting tool, Steeda Sport Lowering Springs, 1 1/8" in the front and 1" lower in the rear, progressive rate, 150-180 lbs./in front and 525-820 lbs./in rear, and lastly, 305-30-19 Michelin Sport 4S at all four corners, basically a square set up. They have the same section width as the RE71R's that the folks at Vorshlag used on their 2018 GT with the F-14's, but the tread on the Michelin's is about .4 mm wider.
My issue is tire rub at the tops of the front fender openings. My alignment shop has been gradually increasing the camber settings which are now currently set at negative camber at -3.70 on the left front and -3.74 on the right front, with +7.01 caster (LF), +6.65 caster (RF), +0.02 Toe (LF), and +0.00 Toe (RF). I have my first track day of this season coming up in July, and with rubbing on spirited back road outings, I'm clearly concerned about taking it to a track session.
I don't really want to purchase a new set of wheels if I don't have to. I see that Ford Performance has a set of Mach 1 cast wheels 10 1/2" wide x 19" fronts and 11" wide x 19" rears for sale. They weigh about 17lbs. more per wheel than ForgeStar wheels. I've been told by several folks that 10 1/2" wide is as wide as one can go on the front and expect not to have any interference.
When I talk with my friends at Vorshlag though, apparently I seem to be the only one who has had any clearance issues with their spec wheels? Maybe a bad set? So, do I keep the ForgeStar's and swap the springs to stiffer units to limit suspension compression? I only track the car a few times a season currently, but with plans to hopefully do more.
I was told that the GT 350R Springs are the stiffest set that one can run with factory struts, 240 lbs./in front and 914 lbs./in rear. Plus I believe that this spring set would return the car to its factory ride height, which maybe could help with clearance?
Do I buy one tire size down with the P4's, 295-30-19 for the front? Is splitting 10 millimeters, 5 inside and 5 outside enough to buy me the clearance I seek? I've been told that the wheel has more of an effect than a tire size change would.
So, I'm not sure where to throw my money next to solve this issue. Less expensive would certainly be the more attractive route. I'm planning on contacting ForgeStar directly to see if they offer a 10" wide F-14 front, that way, I'd be certain to clear the fenders, even though it defeats the purpose of a square set up, probably have to go with a 285 or 275 - 40 x 19" tires though.
Thoughts?