Boinkus44

Definitely replacing all of them. My winter project just became my late season project. Will advise of any info gathered re failure. We put a lot of faith - and not a lot of thought - into a $4 part that has significant safety implications.

deputydog95

Should be about 15 foot pounds. I wouldn't even bother with a torque wrench. Just lightly tighten them by hand with a little pressure at full stop.

chris walrod

It would be nice to know the material and heat treat spec used for these studs. Studs should not fail, especially in an arena such as this as torque wrenches are used each time, I presume.

Are these rolled or cut threads?
ETD150 is an excellent fastener material -- can be machined as is and requires no heat treat.

Just some questions I have.

himself

I replaced the ones on the same axle at the same time (rear). I checked the ones on the front and didn't find them cracking. I replaced the fronts a little later.

With the bullet nose, you need to double up the nuts to apply enough torque to get them seated.

Why is it that studs should not fail? They are just a piece of metal that gets stressed continually. I've had 3 or 4 fail on my car in the last few years. And I've seen way more than that fail on other people's cars. Heck, it seems like a miata loses a stud every event.

-td

FFaust

Cut, rolled are on the way but have not been released yet. And as far as material is concerned, I can tell you that it's hard stuff (maybe that's the problem, too hard and brittle?). Went through at least 10 drill bits to get the extractor in there.

I'm not being flippant here, but bolts don't break. Are there different forces at play with a stud v. with normal bolts?

For the record, I've had two of these break on the same left rear recently at a few track day's interval after 15 to 20 track days. I have been in communication with Bill at ACS, who has been great to deal with. He is investigating, but says that these should not break.

LVDell

Says they shouldn't break but yet they are. Would really like to understand what is at play here.

FFaust

... as would he, I'm sure. He asked me to send him my broken ones for analysis.

LVDell

Sounds good. I'll be anxiously awaiting some finding.

himself

I may still have some heads or tails from my old broken studs. I'll go check it out.

FWIW, one of my mechanical engineering friends that builds helicopters says that these things generally break because of human error in installing/uninstalling wheels. If you get something that isn't perfectly flat or seated just right, driving or installation can create repeated stresses that the stud cannot really handle. When you get a little crack, it will eventually become a big one and shear. Of course, those are my charaterization of his words, which were much more elouent and in engineering-ese.

-td

Boinkus44

Would be interesting to hear from those who have experienced stud failures, which wheel(s) the failure occurred on. FWIW - and recognizing that it is a VERY small sample size - the stud failures (3 out of 3) recently experienced by FFaust and I were all on the left rear wheel. With most track configurations, you would expect this wheel to be subjected to the most stress, so just curious to know if this is being reflected in a bias if left rear wheel stud failures.

And I'll also be following up with ACS re failure analysis and will share results.

JohnPG

Steve & Francois,

I've seen a number of broken studs on some of my track buddies cars. Mostly left rear, but one of my guy has had a number all around this past season.

My mechanic installed these for me at the start of the season. So far no issues even despite and overzealous tech inspection at Mont Tremblant. The tech guy way over torqued my left rear, to such an extent that when I tried to loosen and re-torque my Dewalt wouldn't loosen the nut. I had to use a breaker bar.

I especially like the bullet nose which makes seating the nuts very easy. For the money I think is makes sense to replace on an annual basis.

John

http://www.tcklineracing.com/webdocs...Details364.cfm

Boinkus44

John,

Thanks for the info.

I had exactly the same experience after Tremblant. The torque on the nuts overwhelmed my impact gun and it took a frightening amount if force to loosen them. Had a similar experience with Ferrari tech guys at the Glen this weekend. Definitely not good for stud longevity.

I like the look of the TC Kline studs. Are these what you are using ? and if so, how do you seat them - loctite red or blue or ?

FFaust

Thanks John, and yes, bullet nose is the only way to go.

These TCK studs look identical to my Race-Studs by ACS.

As stated above, I don't understand why studs would break, and not bolts. But yes, replacing them yearly might be a good thing. I was just surprised to get a failure so soon...?

In all fairness, my second failure (pictured below) was also following Tremblant, but nothing to do with tech. A friend wanted to help out so I gave him the pre-set torque wrench. Not sure what happened, but next time I took the wheels off, I struggled, even with the breaker bar???

Now, if I bought a cup car, I would get the proper center-locks, hmmm

JohnPG

Steve,

Yes I am using the TCK studs. I don't know what loctite my mechanic used. Tech inspection can be scary, most of the guys don't know how to use a torque wrench. On occasion I've gone through and have heard the wrench click and then feel the car jerk as the guy on the wrench give it an extra push for good measure , plus who can say if the wrench is calibrated or if its set at the right setting !!!!


Francois,

With regards to them breaking, over tightening them can help, but also I've been wondering if the wrong nuts are used, and I can't claim I've got the proper ones, that might contribute to the issue. I've read somewhere that the nuts have to match the wheel "seat". If the wheel and nut surface are a match that may put more stress on the stud. I don't know if this is the issue, just a thought.

I hear you on the Cup car. It would be nice. Trade off upgrade costs however with motor and tranny rebuilds though.

If you go that way I get first dibs on your wing!!!!

AllanJ

Timely thread. I'm using the ACS studs but have had no problems. However, I just found out my torque wrench is way out of spec and I probably over torqued the nuts a few times. I think I'll be replacing them this winter. Already bought a new torque wrench.