Scott,
Hi.
No, no. You have it all wrong. You put any spring in the car, or any tire on the car, and you are legally able to claim
any amount of drop you want.
Also, you can claim that a 9" drop makes your car handle
like it's on rails.
Okay, on to the real tech.
First: My interests are in handling and real-life street suspensions.
So, my advice is also mainly concerned with those areas. Others likely know more about
suspension setups for the Quarter mile, or mainly for the lowered look.
The stock height for a fox is approx 27-1/4" +/- 1/4".
The amount you can drop the car "and not have problems" varies with the springs, the
suspension setup, and the
intended/desired use of the car.
In general, you can drop a Stang ~3/4"-1" as long as you go with springs that are ~20% stiffer (i.e 600 lbs/in), and you use a bumpsteer kit and CC plates. That's to keep the car "with the same street and
handling characteristics" as the Stock GT. IMHO, most people are full of it when they claim that their car handles better than stock.
Please realize that the GT is already a lowered platform.
And that the ***s that call the GT a "4x4 stance" don't have the slightest clue about automotive suspensions.
The tires/rims that will fit on any Stang (lowered or stock) depend a lot on the
year of the car, the specific car and how it's
tolerances added up, and the specific rim and the
exact tire chosen. In other words, just because "Mike" has the same year car and springs, that doesn't mean that you can run "Mike's" tire/rim setup on your car without any problems. Sorry, but that's the real truth. You can get an "idea" of what fit from other people. But, in reality, anything other than the stock tire and rims get into the build tolerances of the Stang!
As for your specific setup, I'd like to see the rear closer to the same height as the front (26"). Then, I'd suggest a good CC plate (MM), and bumpsteer kit (MM). Also, you should have a front spring rate of at least 600 (Mach1/Bullitt rates). Otherwise, on the street, you'll be very likely to bottom out the
suspension/frame on a big pot hole. On the street, you need to keep the amount of force required to achieve full jounce similar to the stock setup.
The above is why the
Ford Engineers lowered the Mach1 and Bullitt ~1/2 and 3/4" and went to 600 lbs rate springs. Note that the Mach1 and Bullitt already had the "3rd generation spindles" (96-04) for reduces bumpsteer and ackerman change. And, the sn95 platform could support proper alignment with CC plates.
Also, if you look at the ride height of the 95 Cobra R - a car sold only to race teams and made for circle track racing, you'll notice that Ford did
not slam their race car. They also went to even stiffer springs. Although, it's debatable if the springs were still too soft for a
dedicated race car. Race
suspension setups are partly religious beliefs.
As I said, it depends on
your intended/desired use of the car. Some people want the lowered look, and don't car about handling as much. Some people want a pure handling car, and don't mind driving around with harsh 900+ rate springs on the front. For me, I want a better handling car, that isn't "super harsh" when driving in the POS New England states. I often tell people that the New England roads are pot holes connected with small patches of asphalt.
And, yes, I do put my money where my mouth is:
Mustang 86 - Mach1 Springs
Good luck!
