1/2"-20 Wheel Studs

[DPDISXR4Ti]

Is anyone on here actually running with half-inch studs in place of the stock 12mm? Did you find any with the same knurl diameter as stock or was boring required? Or did you go with the screw-in type?

[John V]

14 x 1.5 here..

Why would somebody go 1/2"...not worth the bother.

[DPDISXR4Ti]

14 x 1.5 here..

Why would somebody go 1/2"...not worth the bother.

I need to go with longer studs, so it's not a question of bothering or not. I'm sure I could stick with 12mm and be fine, but figured I could just as easily go 1/2". There's many more options on knurled diameter with a 1/2-20 stud and that may be a factor when I go to re-drill front Scorpio hubs for 4x108 and re-use one of the holes.

My other Euro cars have use a 14mm stud, so it's certainly not a bad idea, just not one I'll likely pursue. Will wheels designed for a 12mm stud need to be over-bored to clear a 14mm?

[timxr8]

The stock hole is drilled to 1/2" for the knurl, so I doubt there is a 1/2" stud that'll be a direct fit. Our 12mm studs are the same as most modern GM cars (why ARP has studs in "our" size). Are you breaking them? Just curious.

[John V]

14 x 1.5 here..

Why would somebody go 1/2"...not worth the bother.

I need to go with longer studs, so it's not a question of bothering or not. I'm sure I could stick with 12mm and be fine, but figured I could just as easily go 1/2". There's many more options on knurled diameter with a 1/2-20 stud and that may be a factor when I go to re-drill front Scorpio hubs for 4x108 and re-use one of the holes.

My other Euro cars have use a 14mm stud, so it's certainly not a bad idea, just not one I'll likely pursue. Will wheels designed for a 12mm stud need to be over-bored to clear a 14mm?

Some but not all..When you need something that long what I've done in make the hole thru the hub AND the spacer undersized by about .002" of the part of the bolt that is not threaded, the get M14 BOLTS, chuck them up and knock the heads off till round, maybe reduced head height and make it a press-fit thru the hub and the spacer so its a unit--like a composite part.. I even made a lead on the tip of the stud for easy nut engagement

Ther was some piccies of a Xratty guy Matt Watson up in Calgary who is an ex-Saab guy and who drove down and hauled back a car load of wheels and when he came I made some combination spacers and "em-biggeners" for the hubs cause he want to go to Saab's 4 on 4 1/2 in bolt circle and there really isn't safe amount of steel in the hub if we do that..
Very easy and with bolts there threads are likely rolled threads, and thus stronger...and certainly cheaper.

[Grayson]

Brad I ended up using 1/2" wheel studs one time because there are long 1/2" studs available with a MASSIVE knurl diameter. I believe they're for a Chrysler application, but it's been a long time since I bought them and I may not be remembering correctly. Anyway, the knurls were so big that I could have holes milled in the wheel flanges on a 4x100mm bolt circle that almost (95%) completely gobbled up the existing 4x108mm holes. So, I performed a 4x100mm conversion using 1/2" studs. 4x100mm wheels designed for 12mm studs bolted up without issue to the 1/2" studs with lug nuts of the proper seat angle.

I can't think of any reason to use 1/2" studs on an XR unless you were trying to take advantage of this odd, large-diameter knurl stud like I was. There may be a good reason, but I haven't envisioned it.

[DPDISXR4Ti]

When you need something that long what I've done in make the hole thru the hub AND the spacer undersized by about .002" of the part of the bolt that is not threaded, the get M14 BOLTS, chuck them up and knock the heads off till round, maybe reduced head height and make it a press-fit thru the hub and the spacer so its a unit--like a composite part.. I even made a lead on the tip of the stud for easy nut engagement

Makes sense for that approach. And/or if I was using Saab wheels, designed for 14mm studs, I'd certainly be all the more inclined to go with 14mm studs.

But what I'm planning to do is re-drill the Scorpio front hubs for 4x108, but re-use one of the existing 5 holes as a starting point. But to do that I'll first need to re-center that first hole (to get it on the 108 circle rather than 112), and then bore to required knurl diameter. From there, turn the rotary table 90 degrees 3x to get the other 3 holes freshly drilled.

I was going to do this for the rears also, but the Scorpio rears are already so swiss-cheese like I just opted to get Sapphire rear hubs and call it done.

[DPDISXR4Ti]

Are you breaking them? Just curious.

No, just needing longer than stock so they're coming out regardless. Figured I'd make a modest upgrade in diameter size as long as they were coming out. An added bonus is the huge variety of available studs/lugs in the 1/2"-20 size.

[John V]

When you need something that long what I've done in make the hole thru the hub AND the spacer undersized by about .002" of the part of the bolt that is not threaded, the get M14 BOLTS, chuck them up and knock the heads off till round, maybe reduced head height and make it a press-fit thru the hub and the spacer so its a unit--like a composite part.. I even made a lead on the tip of the stud for easy nut engagement

Makes sense for that approach. And/or if I was using Saab wheels, designed for 14mm studs, I'd certainly be all the more inclined to go with 14mm studs.

But what I'm planning to do is re-drill the Scorpio front hubs for 4x108, but re-use one of the existing 5 holes as a starting point. But to do that I'll first need to re-center that first hole (to get it on the 108 circle rather than 112), and then bore to required knurl diameter. From there, turn the rotary table 90 degrees 3x to get the other 3 holes freshly drilled.

I was going to do this for the rears also, but the Scorpio rears are already so swiss-cheese like I just opted to get Sapphire rear hubs and call it done.

OK. I strongly reccomend you get a proper sized end mill that cuts on the face and PLUNGE the hole you're beginning with. Things always want to wander when you have a partial hole. And lock the table down once you have zeroed.. I assume you're going to give each stud head a little "love-zaaap" for security..

I always center drill/counter sink first so the drill doesn't wander off.


Then pilot with something like 5/16 or 3/8, then the last hole is a easy pass thru..

[DPDISXR4Ti]

OK. I strongly reccomend you get a proper sized end mill that cuts on the face and PLUNGE the hole you're beginning with. Things always want to wander when you have a partial hole.

It's because of the potential for wandering that I would first open up the hole inwardly (one of the existing 5 I'm going to re-use), to a slight oval shape. It looks like I'll be able to plunge with a 1/2" end-mill and then cut 2mm towards the hub center. That'll create the aforementioned
oval hole, which will now be properly centered on the required 108 circle, and thus boring to the new required knurl size won't have a risk of running away.

Continuing further, the newly created oval hole will have a maximum diameter of .578, so that would allow me to use commonly available 1/2-20 studs with a ~.590 knurl diameter. (.582, .585, .589, .594 are all readily available - I'll probably make my choice based on what bit I may already have. Need to know how much interference I should look for between stated stud knurl diameter and tool.

That's probably what your saying in fewer words John, I just figured I'd spell it out with some actual numbers to work through the exercise, both for myself and anyone else who might ever want to do this.