Spindle Stud Replacement for IRS

[Cleve]

Why is Factory Five recommending changing the studs on the rear spindle?
The studs that came with the spindle fit my rims and lugs perfectly. It took 16 complete turns to seat the lug nuts on the rim and its a snug fit. Where as, the replacement studs ,do fit the lug nuts, but with a slightly sloppy fit. The lug nut is capturing 13/16" of thread on the stud. (after 16 turns) .
What is the advantage of changing the studs.? The replacement studs dont look as beefy as the ones already on the spindle. Is it necessary?

[OB6]

It's so you have the same size and thread pitch as the front.

[edwardb]

It's so you have the same size and thread pitch as the front.

Correct. With a little more background information: The front hubs are from the SN-95 Mustang and the FFR designed spindles are set up to use them. At that time, Ford used 1/2-20 SAE studs and lug nuts. The "new" (circa 2015+) IRS setup is from the S550 Mustang which is mostly all metric. Those studs are M14 x 1.5. Factory Five provides 1/2-20 studs for you to swap out on the IRS so that all four corners are the same. Technically, you could leave them as is. But mix up the lug nuts... well it wouldn't be good. One and done with the change and don't look back.

[Jeff Kleiner]

And for the record it’s a hub, not a spindle.

Jeff

[Cleve]

Got it, Thanks.

[Cleve]

Thanks for the detailed answer. Very helpful.