Depends.
I don't think there was ever a "Cobra
R 4-lug" rim.
So, a lot will depend on the
backspacing of the rim.
I'm assuming it's a stock '85 GT/4-cyl setup up front (k-frame, spindles (87-93 are the same), etc)?
Also... why a 9" Cobra R 4-lug? I don't think that Ford sells a 4-lug rim with the official Ford Cobra R emblem.
So, then, why a 9" rim, and not an 8" rim
???
Now, onto wider tire on Mustangs/cars...
It depends on the
exact tire she wants to run. And, I do not mean just the size/width. It's
pure BS that a 245/24/17 tire is "x wide" and "y tall". The same is true for any "size" tire. Check tirerack for tire specs.
It also depends a lot on the exact fenders and exactly on how they where put on and lined up. Many people with 4-eyes that "brag" about their big front tires will either trim the fenders, or push out/extend the bottom bar on the bottom on the fender (just in front of the tire). They also use spacers, rack limiters, and you rarely see then say the
exact brand/model/year of the tire and the exact air pressure in the tires, if they have the lip pushed in, the
exact height of the fenders with the car on level ground, and so on. And, yes, the year tire does make a difference since tire models change over the years.
So, be very very very very very careful about people telling you that you can put 335's on the front of a 100% stock 4-eye and it rides fine!
Also, is the car lowered? From '85, the lower isolators are likely gone. So, that will drop the front by very roughly 1/10" -> 1/4".
I've seen
cheap *ss POS 245/45/17 tires that are as thin as a stock 225. So, again, the
exact tires make a big difference.
Wider tires can be a problem with rubbing on the fender over bumps, or if the tires are turned and the car goes over bumps.
For example, when I got a new set of 17" Blizzaks snows, they were a
tiny bit wider and taller than the same exact model and size that I got ~4 years earlier. So, the new tires had to go on the back, and I had to put the slightly worn back Blizzaks on the front. (I like to be able to drive my Stang about once every two weeks in the winter if the roads are nice and the weather is good.
)
Last, here's my car:
Mustang 86 - Mach1 Springs
1986 Mustang, sn95 5-lug setup, Cobra M2300K brake kit, ABS,
Mach1 Springs, Steeda 1/4" front spring spacers (placed on
top of the isolator),
The front fenders sit ~26-7/8" from the ground and that's with 245/45/17 RE730s (@32 PSI) which are the correct diameter for the car.
The Mach1 springs are rated at 600lbs/in vs the 425/530 lbs/in stock GT springs.
Good Luck!
