89 Foxbody W/ 03 Irs Wheel Fitment?

Michael West · Jan 11, 2014

Hey everyone, im new here and thought this would be a good place to clear some things up about my wheel fitment and get some advice from others.
I've got an 89 mustang with an 03 cobra IRS in the rear and its lowered quite a bit. As of now its just on some 96 gt wheels, but id like to get some aftermarket wheels and wide tires on it. From what Ive found researching, the IRS is 1.5" wider on each side, so fitting 10" wheels is "almost impossible" without sticking out past the fender.

If you guys could give me some ideas and information about wheels that I can fit on my car i'd really appreciate it. Im sort of lost right now.

stykthyn · Jan 12, 2014

IIRC a 9" wheel is the widest you are going to fit with that rear. Why not some 10th anniversary cobras ? They were made for that rear and look bad ass.

reece146 · Jan 12, 2014

Can't get away with a roll and pull?

Have you done the maths on what offset/backspacing a theoretical 10" wheel would require to fit your setup?

As modern cars go to larger and larger offsets (+60 - +70mm) there must be something that comes close?

You could flare the rear openings also. This car has a really nice rear flare done to it:

http://www.firsttraderegistry.com/forsale/10_11/93mustang/

It is nice and subtle. Combined with a front fender pull and roll I'm hoping to run a 255 square setup for on road and a 275 square setup for on track. I haven't gotten far enough to provide any advice though - still need to buy the car.

Just some thoughts.

stykthyn · Jan 12, 2014

The problem isn't going to be with the fenders, its going to be hitting on the inside.

reece146 · Jan 12, 2014

But then less backspacing and moving the wheel outboard with flares should work, no?

stykthyn · Jan 12, 2014

Corral.net has a huge wheel/tire forum and this topic has been covered several times by people that have done the swap.

RacEoHolic330 · Jan 12, 2014

There are a good number of setups that will work with the IRS. I've never seen anyone with larger than a 18x10" and 285 tire out back. That was with custom wheels to get the backspacing absolutely perfect. That setup also pushed the tire out basically flush with the fender and creates minor rubbing during hard cornering. As the IRS moves over bumps, the wheel gets pushed outward slightly as the suspension compresses over a bump or in a hard corner.

With off-the-shelf wheels, S197 wheels would probably be your best bet. Most of the factory wheels have 45mm offset compared to the 28-30mm offset of the earlier Ford wheels. That's not to say the earlier wheels won't work, they will just sit more flush with the fender. The tire size and brand can make a big difference too. Some run more narrow than others. The limiting factor is the upper subframe mount. It sticks out past the inner fender well. In hindsight, I should have welded my own bracket together to eliminated that upper mount to create more space.

I was originally going to run 01 Cobra wheels. (17x8" 5.72 BS, et30). With a good amount of negative camber and 245/45/17 wheels, they fit pretty well. They sat out about as far as I would like. I decided to change my setup around and go with 18x9" wheels and a 275 tire out back. This required custom wheels. The 275's fit so tight that I had to use a wheel fitment tool to make sure I get the backspacing perfect.

Here's the tire mocked up. No room to spare.

18x9" with 6.35" BS came out to be my magic number. Hopefully everything fits. We'll see once I get the wheels.

stykthyn is right about the Wheel/tire section on corral. There are a few threads regarding IRS tire fitment. Basically, the bigger the tire, the more trouble you're going to have finding wheels.

Michael West · Jan 12, 2014

Well, this car is my daily driver, so I would like to avoid rubbing as much as possible. I was looking around online and all I could find with a 45mm offset are these American Racing Torq Thrusts... http://www.ebay.com/itm/AMERICAN-RA..._Car_Truck_Wheels&hash=item20cf80dcd3&vxp=mtr

I'm thinking these should fit pretty decent with some nitto nt555 275 40 17 or maybe the 255 45 17? What do you guys think? I really appreciate all the input!! and thanks raceoholic for the pics!

RacEoHolic330 · Jan 12, 2014

Check out the wheels at americanmuscle.com. They list all the specs for the wheels they carry. You can't go based on offset alone. It varies too much. Backspacing is the number to keep in mind. Any 9" wheel with a BS of 6.15" (flush with fender) to 6.50" (tucked in more) should work. Going with 255's will help with the inner fender clearance. 6.50" may cause some inner rubbing depending on the camber.

Michael West · Jan 12, 2014

Alright, and do you think I should look at the 18" wheels too? I would prefer 18's, Im just not sure about the clearance..

Michael West · Jan 12, 2014

found these sve drift wheels in 18x9, 35mm offset with 6.38" backspacing! I love them, and it even says it will fit foxbodies with sn95 front 5 lug conversion, which is what I have! Do you think these will work for me with my ride height where its at?
http://www.latemodelrestoration.com/item/SVE-1007FC/2005-12-Mustang-Flat-Black-SVE-Drift-18X9

2000xp8 · Jan 12, 2014

So many times i've thought about going to an IRS, i'm just not willing to give up my wheels.

Those SVE wheels you just posted look pretty nice.
Lowered for the most part is lowered. So your ride height shouldn't affect fitment. Your tire choice will though.

In the link reece posted, those fenders look horrible, always wondered what that would look like, now i know, not good.

Michael West · Jan 12, 2014

OK, so if I were to use the AMR drift wheels off American muscle (http://www.americanmuscle.com/black-amr-18x9-0513.html), and go with 18x8 in the front and 18x9 in the rear, what would be my best tire choice? what I have in mind is a 225-40-18 in front and a 255-40-18 in the rear..

reece146 · Jan 12, 2014

Yeah, he's added a lot more flare than necessary for the wheel/tire combo.

stykthyn · Jan 12, 2014

Honestly I would go with the smallest width tire that would safely fit.

Michael West · Jan 12, 2014

what would be the smallest safe fit on the 18x9?

2000xp8 · Jan 12, 2014

Michael West said:
OK, so if I were to use the AMR drift wheels off American muscle (http://www.americanmuscle.com/black-amr-18x9-0513.html), and go with 18x8 in the front and 18x9 in the rear, what would be my best tire choice? what I have in mind is a 225-40-18 in front and a 255-40-18 in the rear..

You sure you belong on stangnet?
Someone choosing tire sizes on the conservative side here is quite the anomaly.
Most want to run 315's then expect not to tear up tires.

Those sizes should work, i run a 225 40 18 on the front with an 8.5 wheel.
275 35 18 drag radial on the rear 8.5 (runs wide and rub a little on inside).

For a daily driver or a street car driven alot, those sizes should leave you a little wiggle room, which is good.

Michael West · Jan 12, 2014

Trust me I WANT to get as much tire as I can back there, I jut don't wanna be rubbing like crazy

Michael West · Jan 12, 2014

And thanks for the help by the way

2000xp8 · Jan 12, 2014

Wide tires are cool and all, but an extra 20mm's makes no difference.
I wish bfg still did the 265 35 18 DR's, because that's what i would use.

89 Foxbody W/ 03 Irs Wheel Fitment?

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