Keep breaking lugs - advice for hardened lugs??

[maestromaestro]

Curious if a slightly miss-drilled/aligned 4x100 pattern be part of the problem.

Ok. No - these were done in a reputable machine shop. Good thought though. Didn't have this problem until I busted the two Motegis on the front and switched to Focals - because, of course, Motegi stopped making the wheel I needed.

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[Solort]

After reading title, I was going to recommend a good laxative, but after reading posts, I may have misinterpreted "hardened lugs" as a new slang term...

 

[neeqness]

Ok. No - these were done in a reputable machine shop. Good thought though. Didn't have this problem until I busted the two Motegis on the front and switched to Focals - because, of course, Motegi stopped making the wheel I needed.

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If you don't mind, which Focal are you running? Just curious because I'm running Focals too.

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[BRGT350]

I believe that the rings are the source of the problem. There is no lateral load; it is a cantilever beam situation, with the threads acting as "stress risers". Added vibration (stress) causes the number of cycles to exceed the fatigue limit on the S-N curve, if you'd like to get technical about it.

I have autocrossed and done track events with and without hubcentric rings on aftermarket wheels with stock Ford studs and have never broke one. Are you using any anti-seize or friction modifier on the studs? If the coefficient of friction changes and the torque applied stays the same, the actual induced tension in the stud increases. Are you checking the torque when the studs are hot? In the 20 years that I have been running autocross and track events, mostly all with aftermarket wheels that are hubcentric, I have yet to break a stud or have one come loose.

 

[westcoaST]

The photo on page 1 shows at least one instance of bending fatigue. I would need to see higher mag. Photos of the rest of the studs, but it looks like a bolt circle problem. Or a wheel problem. They are not lining up. Get a dial indicator on a magnetic base and indicate on the outside of the stud. Then zero the dial, then measure the rest of the studs using this method. Same thing should be done on the wheels.The initiation site is near the I'D along a line drawn from the center of the hub to the broken stud at the top right position of your photo. FYI I am a metallurgical engineer. Look me up on LinkedIn. Frank Reyes. Most of your explanations contained a bit of fact, but the failed studs will always tell one the real reason for the failure.

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[maestromaestro]

No, nothing like friction modifier. It is likely a perfect storm - the stud material itself and the wrong centering rings. The notion of torqueing nuts hot is not lost on me - I didn't do that though. For now - with the proper centering rings and frequently checked torque, it seems to work. No failures so far.

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[PhoenixM3]

This is not a torque wrench issue. To answer your question, these are brand new (less than a year). The lug nuts are proper - the seat matches the wheel. And, metallurgically speaking, these are high-cycle failures, and have nothing to do with torquing. The nuts would have to be quite loose to arrive at this. And, just because you haven't heard of anybody breaking studs, doesn't mean that this can't happen - clearly, it is an issue here. I am fairly certain that this is an issue of mismatched (bad tolerances) centering rings. I have new coming in tomorrow - so, we'll see. [Notwithstanding the root cause, the quality of Ford studs leaves much to be desired.]


My question was, however, if anyone has suggestions on the stronger studs - still wondering.

Do you only have this problem with your set of race wheels? I have 20+ laps at the Ring with stock wheel setup. And do believe the issue lies with the wheel selection and/or torquing procedure. I too torque to 100lbs with a basic tool and have never, ever even heard of this issue on a Fiesta.

 

[maestromaestro]

Do you only have this problem with your set of race wheels? I have 20+ laps at the Ring with stock wheel setup. And do believe the issue lies with the wheel selection and/or torquing procedure. I too torque to 100lbs with a basic tool and have never, ever even heard of this issue on a Fiesta.

Given the phenomenon, it is difficult for me to separate the effect of the two sets - I would need to drive a lot on the racing wheels for this to manifest - as this is a time-dependent mode of failure. And, as I noted, this is unlikely to occur for a stock setup, as the stock wheels are hubcentric.

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[maestromaestro]

The photo on page 1 shows at least one instance of bending fatigue. I would need to see higher mag. Photos of the rest of the studs, but it looks like a bolt circle problem. Or a wheel problem. They are not lining up. Get a dial indicator on a magnetic base and indicate on the outside of the stud. Then zero the dial, then measure the rest of the studs using this method. Same thing should be done on the wheels.The initiation site is near the I'D along a line drawn from the center of the hub to the broken stud at the top right position of your photo. FYI I am a metallurgical engineer. Look me up on LinkedIn. Frank Reyes. Most of your explanations contained a bit of fact, but the failed studs will always tell one the real reason for the failure.

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It is clearly an instance of fatigue. The may be some run-out with the wheel/studs, but - following the Occam's razor principle, my money is on the mismatched rings and the wheel hubs. For about 200 miles now I am on a properly sized rings - no problems so far.

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[PhoenixM3]

Given the phenomenon, it is difficult for me to separate the effect of the two sets - I would need to drive a lot on the racing wheels for this to manifest - as this is a time-dependent mode of failure. And, as I noted, this is unlikely to occur for a stock setup, as the stock wheels are hubcentric.

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Ok. So you haven't observed the issue with stock wheel setup. How many miles elapse before you notice a broken stud? Not the same wheel? Or could the problem be traced to a single wheel, which may be the bad one.

 

[maestromaestro]

Ok. So you haven't observed the issue with stock wheel setup. How many miles elapse before you notice a broken stud? Not the same wheel? Or could the problem be traced to a single wheel, which may be the bad one.

Both sides had broken studs - but, again, only for the Focal wheels on the front. The Motegis in the rear, which had the proper hubcentric rings never had the issue. For that matter, prior to my breaking both front Motegis, I hadn't had the problem there either.

Thus - the root cause of the failures is very clear to me. As to how many miles it took to break, I am not exactly sure - my guesstimate is somewhere around 600 to 800. And, the second failure - once one of the bolts goes - is much quicker than the first, because of the increased stress on the remaining studs.

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[maestromaestro]

If you don't mind, which Focal are you running? Just curious because I'm running Focals too.

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Focal 421B X Satin Black Wheel (16x7"/4x100mm, +42 mm offset)

 

[maestromaestro]

Well, it has been several hundred miles on the proper centering rings - and I have been checking the torque every couple of days, to be sure - so far, no more lost studs. I guess this confirms the root cause.

 

[Nightcrew13]

Anyone have the PN for ST wheel studs?

 

[M-Sport fan]

Also, while we're on the topic of factory steel lug studs;

Is there ANY concern for even a chance of; galling, cold welding, or any other problems with using, quality made, 304 grade STAINLESS STEEL lug nuts on the factory studs??

 

[Zormecteon]

This is the kind of application for which Stainless Steel is not the right thing to use. This is where you want Grade 5 nuts. Stainless is too brittle. Stronger yes, but....

At least that's my belief at this moment. Someone else with real knowledge may weigh in and correct me.. .. .. It's just that I've seen the tendency to go for SS in automotive applications where there will be stress loading and have heard tell of the breaking off. .. But they probably won't gall.

 

[thePete]

Stainless will gall without anti seize and anti seize on wheel studs is stupid.

Professional mechanic, Id just like to chime in that every time I've seen a broken stud it was due to improper torquing or wheel spacers. I see thousands of vehicles a month of all shapes and sizes, from 800hp mustangs to 3 ton F550s.

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[maestromaestro]

Anyone have the PN for ST wheel studs?

ACPZ1107B

You can get them at Tasca, but it is faster (and cheaper) to pick it up at the nearest dealer after buying them on fordparts.com. You just select the dealership to which they would need to be delivered. Oddly, these are not a stocked item in all of Houston - and the dealership wanted almost 3x what these go for on the fordparts.

 

[maestromaestro]

Also, while we're on the topic of factory steel lug studs;

Is there ANY concern for even a chance of; galling, cold welding, or any other problems with using, quality made, 304 grade STAINLESS STEEL lug nuts on the factory studs??

I don't see the point in using them. There are Mg or Ti lug nuts "out there", but these are on 'exotics', in the pursuit of weight savings. SS lug nuts would be softer, but here is something to consider - these can pit if road salts are present. There are some other concerns, like galvanic corrosion, but these are finer topics...

 

[maestromaestro]

This is the kind of application for which Stainless Steel is not the right thing to use. This is where you want Grade 5 nuts. Stainless is too brittle. Stronger yes, but....

At least that's my belief at this moment. Someone else with real knowledge may weigh in and correct me.. .. ..

Ok - here is the correction. SS is not stronger than CS (grades and heat treatment need to be considered, as is cold working of SS, but - in general, not stronger), and it is not any more brittle. Typically, the stronger the material, the more it is susceptible to brittle failure.