Wheel Size with IRS

[Real Time]

Hi ALL,

I see you guys say 94 to 2004 mustang will be the correct wheel size for the MK4.
The IRS on the order sheet says It's 2015.
Do they still call for the same size wheels?

Thanks in advance!!

[Jeff Kleiner]

Unless you use different brakes the 2015 and later derived IRS requires 17” or larger rims. The 1094-2004 rear ends can use 15” rims.

Jeff

[GTBradley]

I was looking to see what it was about the IRS that restricts the wheel size just the other day. It looks like it is the lower control arm and knuckle pivot point. It is far enough inboard that it makes me think that thinner rear wheels and maybe spacers might allow for 15" wheels, anybody know?
177060

[Real Time]

Unless you use different brakes the 2015 and later derived IRS requires 17” or larger rims. The 1094-2004 rear ends can use 15” rims.

Jeff

Thank you Jeff,
It looks like I'm going with 17's from American Muscle.

https://www.americanmuscle.com/mustang-staggered-deep-dish-2003-cobra-style-chrome-4-wheel-kit-17x9105-390456.html
-OR-
https://www.americanmuscle.com/mustang-staggered-bullitt-chrome-4-wheel-kit-17x9105-390452.html

George

[frd2]

My 17" wheels BARELY clear the caliper (mustang, not ffr) to the point that I can't run wheel weights in that area.

[CraigS]

When I did an irs retrofit on my MkII I had a problem w/ the rear wheel touching the outside of the caliper. The caliper was the stock unit that came w/ my salvage rear suspension. So I did some grinding on the caliper. What I had failed to realize was that the wheel that interfered was my oldest which I 'think' I had gotten from OE wheels. The other two sets (from American Muscle) cleared. Mine were the style of your second link although a different color.