Irs question

[1charlesjay]

If the Irs uses 2015 spindles and breaks. And the front can use up to 2004 spindles and breaks. How do you buy wheels? Are they 2 of each? Seams it would be hard to get the same style in all 4

[1charlesjay]

Correction brakes

[Hoooper]

They are the same bolt pattern, buying wheels isnt an issue. FFR has set up the irs so that the WMS to WMS is the same/similar to the other standard rear configurations. If you are concerned about caliper clearance, you can get rear brake setups for the 2015+ IRS for down to 15" wheels, I think the standard size is 17" minimum.

[edwardb]

The only difference is the stud threads. The front spindles have SAE 1/2-20 threads. The newer 2015+ IRS hubs are metric. Factory Five includes new SAE studs to swap them out. Discussed frequently on the forum, but not hard IMO. If you buy wheels from Factory Five, they will come with all SAE lug nuts.

[alexmak]

The only difference is the stud threads. The front spindles have SAE 1/2-20 threads. The newer 2015+ IRS hubs are metric. Factory Five includes new SAE studs to swap them out. Discussed frequently on the forum, but not hard IMO. If you buy wheels from Factory Five, they will come with all SAE lug nuts.

Physically swapping the studs was probably the hardest thing we had to do, and we gave up in between and asked friends from a nearby garage to help out

[CraigS]

FFR has wheels as do many other Mustang parts sources. I usually buy here;
https://www.americanmuscle.com/dedibuwh.html
https://www.americanmuscle.com/buwh1-9404.html
Fronts are 9x17 or 9x18 w/ 6 inch backspace. Rears are 10.5-11.0 x 17 or 18 w/ BS 6.9 or so. Lug pattern is 5x4.5inch or 5x114.3mm.

[1charlesjay]

Wow thanks for all the info. Especially on the exact wheels I want!

[1charlesjay]

I guess this is still an irs question so I'll post it here. What rear ratio would you run with a 347? I see 3.15 center sections reasonable. Would a 3.27 or a 3.55 be better

[edwardb]

I guess this is still an irs question so I'll post it here. What rear ratio would you run with a 347? I see 3.15 center sections reasonable. Would a 3.27 or a 3.55 be better

There's no one answer for that question. Depends on your transmission, tire size (although they do tend to be all pretty close if you're using typical sizes), how you plan to use your car, etc. Lots of discussion on that point. 3.55 is the most popular but guys make cases for other ratios. So you need to do some research and decide from that. But for the IRS diff, the reason the 3.15 is cheaper is (1) they're plentiful, and (2) they can't be modified. They will always be 3.15. Every other IRS diff (3.55, 3.73, etc.) can be swapped to other ratios if the need/desire arises. Something different about the internals, although I don't know the specifics. So that makes them less desirable.

[Dave Tabor]

Why the swapping of wheel studs?

I did not- am I going to have a problem?

Thanks
Dave

Gen III #17

[edwardb]

Why the swapping of wheel studs?

I did not- am I going to have a problem?

Thanks
Dave

Gen III #17

If you use the front hubs provided by Factory Five and don't change the rear studs you'll have SAE threads in the front and metric in the back. (Post #4 above) Yes, you could leave it that way. Just make sure you're using the proper lug nuts on the front and back. And don't mix them up or you will be changing them. It's not hard to swap the rears with the SAE studs provided in the kit. One time and you're done as opposed to being a constant caution. I don't particularly care for the Factory Five instructions (beat them out with a hammer, put them back in with a ratchet and vise) and it's understandable to me why some struggle with it. They're easily pressed out pulled back in with a hardened nut, washers, grease, and an impact wrench. Worst case, take them to your local machine shop. Maybe a 5-10 minute job with a shop press.

[TXJosh]

Hello all
Does anybody know how long are the 1/2-20 wheel studs supplied by factory five for the IRS. Mine were missing from the irs fastener pack so I am, in the interest of time, going to buy 10 studs from summit or speedway.

Has any spendthrift out there actually bought separate hubs with the 1/2-20 studs pre-installed? Lazy question I know, more just a curiosity.

[BUDFIVE]

Tx Josh,
I’m not sure the length of the FFR studs but they are pretty long—the picture is after I installed mine-I may have to cut them shorter to use the spinner style wheel center on my Halibrand wheels. The separate bolt next to my hubs is the original metric stud. Some guys in the forum use Dorman 610-290 which are 2-3/16” under head.
IMG_4554.jpg
Your second question: I don’t think you can buy the hub with 1/2-20 studs already installed—the hub is used on 2015+ IRS Mustangs which used Metric lugs. Prior to 2015, the solid rear axle used 1/2-20 lugs but a totally different hub style.

[edwardb]

Hello all
Does anybody know how long are the 1/2-20 wheel studs supplied by factory five for the IRS. Mine were missing from the irs fastener pack so I am, in the interest of time, going to buy 10 studs from summit or speedway.

Has any spendthrift out there actually bought separate hubs with the 1/2-20 studs pre-installed? Lazy question I know, more just a curiosity.

I had to buy some new studs for the IRS hubs during my Coupe build several years ago. Due to an error on my parts with the FFR supplied studs. No further explanation necessary... I bought Dorman 610-290 Wheel Studs from Summit. Available elsewhere as well. Come in a package of 10 and worked fine.

The 2015+ IRS parts from Ford are only available as metric. As already mentioned. Don't stress over replacing them. I don't recommend hammering on the hubs as the manual describes. They can be pressed out and replaced relatively easily. If you don't have the proper tools, take them to an automotive machine shop. They will make quick work of it and based on other posts here the cost is relatively low.