IRS studs not the same size

[Slider]

Here’s a weird one. I’m using the iRS from factory five so replaced the wheel studs as instructed. Tonight as I’m putting the wheels on I realized that 1 stud on each side is 1/4” shorter than the others? And in fact the stud itself, while the same diameter and thread, is a different stud. See pictures. This seems really odd but given that it is 1 on each side I’m wondering if there is some intentional reason that I can’t think of. Second this shorter stud does not allow enough length for the stud to completely do through the lugnut when tightened. I suspect I should get FF to replace these shorter studs and switch themo out but figured I’d start by asking here.

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[edwardb]

They should all be the same, and should go all the way through the lug nut. I had mixed parts when my Coupe kit arrived as well, although all were long enough. Are you planning wheel spacers? The Coupe needs an inch or so spacers for the rear wheels to be properly placed in the wheel wells. At least with the standard Factory Five wheels and their offsets. If you do end up with spacers, you'll actually be cutting them shorter. At least I had to. So maybe nothing needs to be replaced.

[Slider]

Thanks Edward. I did put an 1/8” spacer in for the FF 17”wheels to clear the rear calipers, but hadn’t heard about the 1” spacer requirement. I guess I’ll call FF tomorrow to get the new studs. And then tear the rear brakes and hub off to replace them. I do get a bit tired of redoing things....

[edwardb]

Thanks Edward. I did put an 1/8” spacer in for the FF 17”wheels to clear the rear calipers, but hadn’t heard about the 1” spacer requirement. I guess I’ll call FF tomorrow to get the new studs. And then tear the rear brakes and hub off to replace them. I do get a bit tired of redoing things....

I'd really encourage you to check into spacers. It's not a requirement. Don't believe it's mentioned anywhere in the manual. But your wheels/tires will be noticeably inside the rear body openings without them. I used the Eibach 90.4.25.010.3 Pro-Spacer Wheel Spacer Kit, 25mm (1 inch). Some go a bit thicker. As you can see from this picture, requires the existing studs to be cut off. The other picture shows where they end up in the body opening. If an inch inside that, wouldn't look quite right IMO (and others). These are 18's. But your 17's would be similar.

[Slider]

[QUOTE=edwardb;372498]I'd really encourage you to check into spacers. It's not a requirement. Don't believe it's mentioned anywhere in the manual. But your wheels/tires will be noticeably inside the rear body openings without them. I used the Eibach 90.4.25.010.3 Pro-Spacer Wheel Spacer Kit, 25mm (1 inch). Some go a bit thicker. As you can see from this picture, requires the existing studs to be cut off. The other picture shows where they end up in the body opening. If an inch inside that, wouldn't look quite right IMO (and others). These are 18's. But your 17's would be similar.

Edward, hate to bother you, but can you confirm this is the right Wheel Spacer Kit? It's a slightly different part #, but indicates it will fit 2015 Mustang IRS https://www.americanmuscle.com/eibac...pair-1517.html

[Alphamacaroon]

That looks really nice @edwardb. I assume it'd be a similar route with the FFR 13" standard rear brakes (assume the center of the rotor is similar thickness)? How hard do you think it'd be cut the studs on the car? I'm not looking forward to pulling the studs out and putting them into the shop press again...

[Alphamacaroon]

@slider, I found the exact part on Amazon for a better price: Eibach 90.4.25.010.3 https://www.amazon.com/Eibach-90-4-2.../dp/B000CN9VRI

Just hit the order button myself.

[Slider]

@slider, I found the exact part on Amazon for a better price: Eibach 90.4.25.010.3 https://www.amazon.com/Eibach-90-4-2.../dp/B000CN9VRI

Just hit the order button myself.

Thanks Alphamacaroon. You just made Amazon yet another sale! I probably owe you a beer somewhere along the way for saving me some $$$

[edwardb]

Edward, hate to bother you, but can you confirm this is the right Wheel Spacer Kit? It's a slightly different part #, but indicates it will fit 2015 Mustang IRS https://www.americanmuscle.com/eibac...pair-1517.html

That looks really nice @edwardb. I assume it'd be a similar route with the FFR 13" standard rear brakes (assume the center of the rotor is similar thickness)? How hard do you think it'd be cut the studs on the car? I'm not looking forward to pulling the studs out and putting them into the shop press again...

Thanks Alphamacaroon. You just made Amazon yet another sale! I probably owe you a beer somewhere along the way for saving me some $$$

No bother. If you go with the Eibach spacers (there are other choices...) you want the Eibach 90.4.25.010.3 ones I listed and pictured. The ones for the 2015+ IRS are exactly the same spacer, but with metric nuts and studs. The 90.4.25.010.3 one is for older Mustangs, but fits the 2015+ IRS just fine and has the 1/2-20 SAE studs which is the whole reason for swapping studs in the first place, e.g. so they match the SAE studs in the front. I bought them on Amazon too BTW.

I believe the same spacers would be OK for the standard brakes as opposed to the Wilwoods. Can't believe there's much difference in the thickness of the rotors. But I have only used them with the Wilwoods pictured. I cut the studs while on the car. No reason to take everything back apart again. I used an air cut-off tool and cleaned up with a file when done. Not hard. Just measure twice (at least) and cut once. The back story for that is in my build thread.

[Slider]

Just closing this out. I talked with FF today. They shared that the supplier did infact supply some incorrect size Studs that snuck out without them catching it. Lucky me. They are sending the replacements now.