Wheel Studs, Lug nuts, and 1.25 fine threads

[Rasmus]

Subaru is a bit of an odd duck when it comes to it's wheel studs, running M12x1.25 bolts. It's not the M12 it's the 1.25 thread pitch that's weird. Now if you're the type of person that takes the wheels off a car only twice a year that fine thread pitch may never be a problem. But if you track, autocross, own multiple sets of wheel/tires for the same car, or wrench on your car alot, you'll remove and reinstall lug nuts dozens of times a year. And when you run fine pitch threads, the risk of cross threading increases. The finer the thread the easier it is to cross thread.

"I'll be careful". Sure. We all say that. But then there's that one time when you arrive late to an event and you need go all "F1-pitstop" and swap to your race rubber. Or you're doing some light wrenching and your brother-in-law want to help, so he pops the lug in the impact wrench socket, turns the psi up to 135, and goes all NASCAR on your ****. Effectively welding the lug to the stud.

What do to?


There's the ARP 100-7716 studs with their bull nose. It's a direct swap out. The bull nose helps to align the lug before trying to engage the threads. You'll need to get a set of open ended M12x1.25 lugs.


Personally I like, and run, Muteki's SR48 lugs on my Daily. They're steel. Aluminum lugs are bad ju-ju and titanium is expensive.

But it's still running a 1.25 thread pitch. Would it be possible to find a set of studs we could run in M12x1.5 or even M12x1.75 instead?


ARP makes the 100-7717. Designed for the Mitsubishi Lancer Evo VIII it's produced in M12x1.50.

But the real trick is can you get it installed in Subaru hubs without welding, drilling, or visiting a machine shop? That is, are the knurl diameters and width the same? According to ARP they are:

Knurl Diameter (in.) 0.565 in
Knurl Length (in) 0.270 in

And M12x1.5 lugs are more numerous than 1.25 so you'd have more selection and cost less.

Confirmed:
ARP 100-7717 Mitsubishi M12x1.5 studs easily press into Subaru Hubs. Perfect fit.

Unconfirmed but 98% certain:
ARP 100-7718 Toyota M12x1.5 studs. Knurl length's a little longer than Subaru's at 8.3 mm vs. 6.9 mm. Subaru's hub flange is 10 mm thick, so it should be fine. Plus the 100-7718 are shorter than the 100-7717 studs. Weight savings? Aesthetics?

[Rasmus]

Also if you don't want to go the expensive route of ARP Wheel studs you could pick up a set of OEM Mitsubishi Wheel studs. Or really cheap out and find a used set Mitsu's.

[Frank818]

That's very nice to know! I will probably not need them as I don't remove the wheels often, but still I am aware.

There is another solution to that problem you exposed. Just don't ask your brother-in-law to help you!

[C.Plavan]

I bought the ARP M12 1.25 before knowing it was 1.25- I would of rather had the M12 1.5 for sure.

[Santiago]

Rasmus, any company can make a printing mistake, but given that the specs are coming straight from the manufacturer who machines these parts, the chances should be good that their specs are accurate. If they say the knurls are the same dia. and length, they should be good to go. The only question should be is there a concern over possible different knurl patterns? Honestly though, I don't know if that's generally a concern or not even if they are different. From the pics they look identical, so I doubt it'll be a worry.

In the end I suspect you're just going to have to play to those odds and pick up a set to confirm it yourself. The upshot is that you don't need a full set for 4 hubs, you just need one to test.

If it checks out, you let us all know (so we don't have to gamble). =)

Best,
-j

[longislandwrx]

Smart idea.

Muteki steel nuts are nice, and you can get them in titanium color... only your hairdresser will know for sure.

[Rasmus]

Smart idea.

Muteki steel nuts are nice, and you can get them in titanium color... only your hairdresser will know for sure.

If only I could get set of PushUpBra wheels. 225/40P17's look like 275/40P17's on PushUpBra Brand Wheels!

[longislandwrx]

If only I could get set of PushUpBra wheels. 225/40P17's look like 275/40P17's on PushUpBra Brand Wheels!

AKA Stance? 225s on 10.5" rim? False advertising

[SixStar]

AKA Stance? 225s on 10.5" rim? False advertising

I have 225s on a 17x9. They made me sign a waiver before leaving with them.

[Bob_n_Cincy]

AKA Stance? 225s on 10.5" rim? False advertising

On my impreza G-stock car I can put any tires on stock size rims.
So I am running 225/45R16 R888 on 6-1/2 rims. I guess you call that a sports bra.

P1040674s.jpg

[apexanimal]

I have 225s on a 17x9. They made me sign a waiver before leaving with them.

Ridiculous... 225s on a 9" are fast on the track... Perhaps a bit much on the street but very performance oriented...

Anything more than that is getting crazy though...

[rallysteve]

I have been using stock studs for about 10 years on my rally Subaru. Only have broken two in that time, both on taking them off. It gets stuck, you just break it off and install a new one. I stick to the factory 75ft.lbs. for my Impreza but check them at every service. Blowing down a logging road at 90 mph is not exactly easy on them, they seem to be fine.

[Bill Waters]

Rasmus - I realize it hasn't been that long since the OP, but is there any further clarification or resolution regarding the M12x1.5 studs and their applicability? I am nearing the point of ordering the ARP studs for my R and your post brings up a very good point.

Thanks, Bill

[Canadian818]

I think bill just volunteered to be the first to try!

[Bill Waters]

Possibly so......

[Rasmus]

Heyya Bill. Sorry I didn't reply sooner.

I put my money where my words are. I purchased the M12x1.5 studs and a set of lugs to go with them. I haven't got around to installing them. Clearly, I assume they'll install without issue.

[apexanimal]

Torque still the same?

[Canadian818]

Let us know when you do Rasmus!

[Rasmus]

I'll shoot this to the top five of my list.


Working toward getting the M12x1.5 studs installed.

[metros]

Post when you get them installed and if they needed anything out of the ordinary.

The evo arp studs any cheaper? I noticed arp stud prices vary quite a bit depending on application.

[longislandwrx]

http://www.ebay.com/itm/ARP-100-7717...-/360516871861

pretty good deal with free shipping.

[Scargo]

To confirm, I have been running the M12x1.50 ARP 100-7717 studs (for the Mitsubishi Lancer Evo) on my STI track car for a full year. Direct swap for the ARP 1.25 studs. Perfect, identical fitting part except for the threads.
Bonus: 1.50 lug nuts are more plentiful with a bigger selection and cheaper, too.
For racing, I run the cheap, extra long, heavy-duty lug nuts from Summit, etc., at a buck apiece. Obviously, these lug nuts will not fit all wheels.

[Rasmus]

Thanks for the confirmation Scargo.

Last I looked at prices was in December 2013:

Muteki sr48 12x1.5 in "Titanium" run $61.54
Muteki sr48 12x1.25 in "Titanium" run $68.16

Muteki sr48 12x1.5 in Black run $52.99
Muteki sr48 12x1.25 in Black run $68.16

The ARP 100-7717 M12x1.5 run $119.88
The ARP 100-7716 M12x1.25 run $129.28

[Scargo]

That about sums it up. Win-win for those in need of studs. Also, though I've not experienced it, I have 3-4 racing buddies who have broken and irreparably cross-threaded stock STI lugs prior to switching to ARP studs. Admittedly, this was with track use and higher than normal frequency of wheel changes.
I would recommend that all people replace their lugs. Think about it: Many of you are using donor suspension parts from wrecked cars. While you have things apart and/or are refurbishing things, changing out the lugs is easy.

[Canadian818]

I'd imagine changing the wheel bearings is required when changing the studs?

[Rasmus]

I'd imagine changing the wheel bearings is required when changing the studs?

Actually, you can change out the studs without removing the hub from the knuckle. That is, you can leave the bearings undisturbed. Just don't try to do it without the axle and axle nut in place. They help hold the bearings onto the race. There's enough room to get the ARP's into the hub with it still on the knuckle.

[Bob_n_Cincy]

Actually, you can change out the studs without removing the hub from the knuckle. That is, you can leave the bearings undisturbed. Just don't try to do it without the axle and axle nut in place. They help hold the bearings onto the race. There's enough room to get the ARP's into the hub with it still on the knuckle.

Is this possible on the rear hubs?

[Rasmus]

Is this possible on the rear hubs?

Yes*. ARP (100-7716) 3 inch wheel stud install on WRX Rear Axles

*small bit of grinding involved.

[longislandwrx]

nice write-up, never saw that on Nabisco... ty.

[Bill Waters]

Hi, Rasmus - I pulled the trigger on the M12 X 1.5 lugs, as well. Not sure when They'll be installed. I would be surprised if they don't fit, as well. Will advise if I install before you do.

Thanks for this suggestion, by the way.

Bill

[Canadian818]

Does anyone make 2" with the bullnose end?

[Scargo]

Does anyone make 2" with the bullnose end?

First, if you have never used extended ARP studs it might help to explain that I have only 1.9" of usable thread protruding from the thick, aluminum rotor hub* when mounted. After my 1" long racing lug nut is fully threaded on I have 1" left for a wheel hub's center section thickness, or wheel's center section thickness and a spacer. That is with me using an ARP 3" UHL (relative overall length) stud (after I subtracted .1" for the lug nut's conical seat).

Subtract around 1-1/8" from ARP's listed UHL length and then compare that to what you have or want for actual usable threads to mount a wheel on.

I found three shorter 12mm X 1.5 ARP studs that will work. The first one, (for a Toyota Celica GTS), that caught my attention has about a 1/16" longer knurl (which shouldn't hurt anything), and it has a 2.34" UHL.
EX.: 2.34"-1.25"=1.09" for wheel and nut. Nuts are usually 5/8" minimum OA length. Accounting for the length of the conical seat angle (60 degrees), might leave you 1/2" for a wheel center section thickness (including any spacer), if you use all of the lug nut's threads. IMHO, that's pretty minimal. (For reference, my Enkei RPF1's are .6" thick)

This one, for a Neon, would require drilling the hub's holes a fraction larger. It is 2.45" for the UHL.
Same would apply for the Miata stud. 2.75" UHL.

Please do your own math and don't take my word for these numbers. Some wheels use straight shank lug nuts.
*FYI, My aluminum Stoptech floating rotor hub is .28" thick. Obviously, many steel centers are thinner.

[Canadian818]

Thanks Scargo! I'll wait to order them until I have all my info. No rush now that I know I can do it on the car.

[DodgyTim]

I tested both my sets of wheels (G2's and Enkei's) on the donor on the weekend.
For both sets the nut had 10 turns from initial engagement to tight, which at 1.25 mm pitch is about 12 mm of bolt length
Given the normal rule of thumb that nut width should be equal or greater than bolt dia, everything is Ok until I factor in the 5mm spacers I need to run. 5mm spacers reduce the nut engagement to just over 0.5 diameter , so it looks like I'll be needing longer studs too.

Another $250 gone once nuts and shipping is included.....

[Rasmus]

To confirm, I have been running theM12x1.50 ARP 100-7717 studs (for the Mitsubishi Lancer Evo) on my STI track car for a full year. Direct swap for the ARP 1.25 studs. Perfect, identical fitting part except for the threads.

Backing up Scargo:


M12x1.50 ARP 100-7717 (Mitsubishi Lancer Evo) studs press easily into Subaru hubs. Went in just like an OEM replacement. Knurl pattern exactly the same.

[Scargo]

When I put mine in I was able to "find" or match up the old grooves with the new knurls. By rotating and slight pressure I made sure they did not create a new home, which I believe would be detrimental. They still went in snugly. How about yours?

[Rasmus]

Same. Just located the knurls into the old grooves by feel and they pressed right in.

[Outwest]

Just installed my arp evo studs today, they went in perfectly

[cycleguy55]

Nissan / Infiniti also uses M12 x 1.25 lugs - had them on our Maxima, and have them on both our G35x and FX35. Yeah, a little tougher to track down nuts, but I switch all the wheels twice each year and have never cross-threaded or stripped a stud or nut.

[Bob_n_Cincy]

Michael and I did out first Autocross of the year today.
We did 25 events last year and had 4 stud problems.
It happened again today.
Showed up 8:30 AM 35f swapped to R888 even though it was to cold for them.
Tighten lugs to 70 ft-lbs.
Did 12 runs in the morning and worked the course in the afternoon.
Still about 35f.
the went to swap wheels before heading back home.
During removal one of the 20 lug nuts froze on the stud after about 2 revolutions.
This is the fifth or sixth time in the in the past year.
My choice at the point is to drive home on race tires on snap off the stud. SNAP The last time this happened I replaced all studs and lug nuts with OEM.

Has anyone else had problems' like this on Subaru's?
I should also add problem is only on the fronts.

Michael kicked my butt today by 1.5 seconds.
Bob