It's amazing that you've had a lot of responses, but nobody has explained the problem you're facing. It's simple. The S550 wheel wells are big enough for big tires, but the rear stub-axle sticks 1-1/4" (32mm) further into the rear wheel well than the front stub axle sticks into the front wheel well. That means, to center the tires up properly, you need a 32mm difference in offset. The rear tire/rim has to be set 32mm further inwards than the front. That's why the GT350 rims are 11" rear ET62 and 10.5" front ET 30 - a 32 mm difference.I'd like to run 305 30 19s square on my Bullitt Mustang. I've searched forum here and have been on a number of different sites seeking information. I've also been to a couple of tire stores and spoken to Tire Rack as well and I'm still not comfortable with what I'm being told.
I want to run this setup WITHOUT spacers on 19 X 11 wheels. The information that missing is what the ET needs to be front and rear.
I'm running Steeda suspension parts including dual rate springs which lower the car 0.5" from stock.
Is anyone running a similar setup on their S550 Mustang?
TIA for all help and information.
Now, if you run a square set of 10" ET37 rims, the inner flange at the front will be the right distance from the strut and the outer flange at the rear will be the right distance from the outer fender liner. No spacers required with that spec. Those 10" rims would easily take 285/35 tires, like the Goodyear 3R or a Toyo R888R. You'd get great great performance and you wouldn't need spacers. But 305's on 11's won't work. At ET37, 11" fronts would hit the strut and 11" rears would hit the fender.