Why change wheel studs for IRS

[Jeff's First FFR]

The existing rear wheel studs are beefier than the FFR replacements. Why change them? Just to match the fronts? I am sure a wheel can fit on the fatter studs. Or not? And why are the Mustang front studs so whimpy? Or not?

[michael everson]

I havent tried a wheel on the bigger studs but I think its just so all are the same. If the wheel fits over the studs, I will just buy the right nuts next time I do an IRS car.
Mike

[edwardb]

What you're seeing is the front hubs Factory Five uses are 1/2-20 SAE threads. Common for that vintage part. The 2015+ IRS hubs are 14mm x 1.50 metric threads, which Ford has switched to. The studs Factory Five supplies for the IRS hubs are the same 1/2-20 SAE threads as the front hubs and makes them all the same, including matching what comes with their wheels if you're using them. You could not change the studs on the IRS and get metric lug nuts for the rears. Personally not my choice. I can just see someone (me included) mixing them up and cross threading something. I haven't checked, but may also use a different size socket. Avoided with one time effort versus dealing with it all the time. Obviously your choice though. There isn't an issue with one being stronger or beefier than the other. Both are more than up to the task.

[Sigurd]

I have 10 Ford Motorsport M14x1.5 lug nuts for next to nothing if interested.

[Jeff's First FFR]

What you're seeing is the front hubs Factory Five uses are 1/2-20 SAE threads. Common for that vintage part. The 2015+ IRS hubs are 14mm x 1.50 metric threads, which Ford has switched to. The studs Factory Five supplies for the IRS hubs are the same 1/2-20 SAE threads as the front hubs and makes them all the same, including matching what comes with their wheels if you're using them. You could not change the studs on the IRS and get metric lug nuts for the rears. Personally not my choice. I can just see someone (me included) mixing them up and cross threading something. I haven't checked, but may also use a different size socket. Avoided with one time effort versus dealing with it all the time. Obviously your choice though. There isn't an issue with one being stronger or beefier than the other. Both are more than up to the task.

Probably a tire store person would mix them up and screw up everything with an impact wrench. SOP: "Better safe than sorry". Thanks. And then there are the brake rotors.

[Jeff's First FFR]

Probably a tire store person would mix them up and screw up everything with an impact wrench. SOP: "Better safe than sorry". Thanks. And then there are the brake rotors.

The rear brake rotors have 16.2mm (0.64") holes in them. Seems sloppy for 0.5" stud. Hmmm

[CraigS]

The rear brake rotors have 16.2mm (0.64") holes in them. Seems sloppy for 0.5" stud. Hmmm

Hopefully your wheels will be hub centric.

[edwardb]

The rear brake rotors have 16.2mm (0.64") holes in them. Seems sloppy for 0.5" stud. Hmmm

Hopefully your wheels will be hub centric.

You're right. Oversize holes like that would be totally unacceptable. If the rotor were actually aligning on them. But they're not. As CraigS said, the alignment is on the hub and should fit accurately. The holes for the studs provide clearance and anti-rotation. Once the wheel is on and lug nuts tightened, they're locked down. Related to this, if you happen to need or use wheel spacers, also make sure they're the hub centric variety. Some, especially the cheap ones, aren't.

[Jeff's First FFR]

You're right. Oversize holes like that would be totally unacceptable. If the rotor were actually aligning on them. But they're not. As CraigS said, the alignment is on the hub and should fit accurately. The holes for the studs provide clearance and anti-rotation. Once the wheel is on and lug nuts tightened, they're locked down. Related to this, if you happen to need or use wheel spacers, also make sure they're the hub centric variety. Some, especially the cheap ones, aren't.

Thank you again. I'm still learning