5 sheared studs and the wheel falls off...

[BAC5.2]

Snap On Torque Stick Set

 

I don't understand the exact science behind how they work, but they do work....The way it was explained to me is that the center shaft of it flexes onces the bolt gets to a certain torque. If you look closely at the set, you will see that the extension on each one is a different diameter.

 

If you use impact then torque wrench, you have no way of knowing if its over spec (and probably is). When you set your torque wrench at 80lbs (standard honda torque for a lug) and it clicks right away, its just telling you your torque is at least 80lbs. If you use a torque stick on your impact, it will get it at 80lbs (plus or minus a few lbs). At first I would double check with a torque wrench, but I've never had anything off by more then a few lbs.

 

The science is simple. A rod of known geometry and material will elastically deform under torsion a specific amount. Thinner rods require less torque to deform. Thicker rods require more torque to deform.

 

A "75 ft-lb" torque stick will elastically deform under 75 ft-lbs of input torque. Impact wrenches work by literally cycling impact. You have an impulse torque, and that's where you get these absurdly high numbers from. There is a latency between impulse events (latency of rotation), so the torque stick merely deforms some angular offset greater than the minimum rotation latency of a single impact preventing anything more than 75 ft-lbs from being transmitted through the shaft of the torque stick. Torque sticks only work for impact applications. Mechanically, they don't work for continuous torque application, so they couldn't replace a torque wrench.

[rob]

This is almost always caused by over torquing the lugs. Service shops love to use their air guns without torque wrenches to put on lugs to save time. I have had to stand on a breaker bar to break lugs free on my cars sometimes.

 

 

So the morale of the story is, whenever you find this, replace all of the wheel studs, else risk the failure I had.

 

-Rob

[rob]

I use my big impact to remove the lugs, then use my 1/2 impact set at 2 to install them, then torque the lugs to 80ftlbs. After I coat the threads with anti-sieze compound.

 

 

The spec is 65+/- 7 ftlbs (IIRC) and if you use any thread lubricant, you need to drop the value accordingly; for anti-sieze drop by 15% seems to be a good estimate. You are well over-torquing.

 

-Rob

[rob]

In the past 14 months I have since had two additional stud failures since this incident.

 

Quick recap; '05 LGT wagon owned since new 120k miles

 

July '10 : Wheel falls off RR while driving down the highway. All 5 studs sheared off. Replaced all 10 front studs with OE; replaced both rear bearing/hubs (comes with new studs) replaced RR brake rotor. Replaced RR lug nuts.

 

July '11: While checking lug nut torque one stud on the LR snaps off with very little effort. Replaced all rear studs with non-OE, made in USA parts. Replaced LR rotor.

 

Aug'11: Again, while checking torque one stud on the RR snaps off with almost NO effort. I had exactly one wheel off/on cycle for a brake job, a little over a month and maybe 1k miles on these NEW studs!! I did the work myself. Torque properly applied (as with ALL the other times I have ever changed my wheels). I even bought another calibrated torque wrench to double check.

 

I had found a thread that had listed other similar failures on very closely related models on another board. VERY TROUBLING PATTERN HERE!

http://www.subaruoutback.org/forums/66-problems-maintenance/25711-breaking-wheel-studs.html

 

It was in describing my THIRD failure that someone mentioned that I could be UNDER torquing my lugs. I decided to do a little homework and in fact found that the original 2005/2006 Subaru FSM in four separate sections incorrectly lists the lug nut torque at 66 ft-lbs when it should be 81.1 ft-lbs. The incorrect spec is what I have been following more and more stringently as my paranoia of over torquing has grown. How ironic that the tire shop monkey with his torque stick was likely doing better for my car than my fanatical torque wrench tweaking.

 

Digging further I found that Subaru issued a correction http://techinfo.subaru.com/proxy/10156/pdf/18-97-06104073.pdf in the entry fourth from the bottom on page 1. I would also suspect that other '05 and '06 failures I have read about on various forums are due to the same error. Another lesson learned is to check for manual changes and repurchase the changed sections on a regular basis. Although I doubt there are many other torque settings that as critical as this.

 

After researching more, I found that indeed under torquing is a leading cause of stud failure (which I never really thought about). I found this article very informative on the matter; http://www.metalconsult.com/articles/Wheel%20Stud%20Bolt%20Failures.pdf

 

So there you have it. I believe I have come to a conclusion. My plan forward is to again replace all 20 studs (boy that hydraulic press was a good investment) and hopefully put this whole thing behind me.

 

Hopefully this proves useful to others

[TSiWRX]

^ Wow. Thank you!!!! That's eye-opening, as that's something I did not know!

[broknindarkagain]

Its been a year and you're coming back to update?? Thanks!

 

On the topic of anti-sieze, you're not suppose to use any lube on lugnuts.

 

Try calling Subaru of America. They may compensate you for your troubles.

[hadvw]

Thanks for the update! This my first "stud" car - all the previous ones were VWs that have wheel bolts, so it's not something I've had to think about before.

 

Done tons of tire changes for summer/winter tires when I lived in Canada, helping my dad with their Dodge/Honda/VW/Toyota, and we always just made sure things were really tight - probably exceeded 100 lb-ft, etc.. Never a problem.

[RacerX69]

BTW, many heavy duty trucks do not use hub-centric wheels and hub loading but rather, yes, carry the entire load on the lugs.

 

Actually heavy trucks use hub centric wheels with coined nuts (a nut with an integral washer) now. I can't remember when the change was made, about 15 to 20 years ago, but all big trucks ride on them now. No more Budd nuts and wheels.

 

There are still older trucks around that have them, farm rigs and local delivery or small business trucks. Over the road trucks rack up miles so quickly that there likely aren't any more running long haul that have the older lug centric wheel/stud setup.

[RacerX69]

In the past 14 months I have since had two additional stud failures since this incident.

 

Quick recap; '05 LGT wagon owned since new 120k miles

 

July '10 : Wheel falls off RR while driving down the highway. All 5 studs sheared off. Replaced all 10 front studs with OE; replaced both rear bearing/hubs (comes with new studs) replaced RR brake rotor. Replaced RR lug nuts.

 

July '11: While checking lug nut torque one stud on the LR snaps off with very little effort. Replaced all rear studs with non-OE, made in USA parts. Replaced LR rotor.

 

Aug'11: Again, while checking torque one stud on the RR snaps off with almost NO effort. I had exactly one wheel off/on cycle for a brake job, a little over a month and maybe 1k miles on these NEW studs!! I did the work myself. Torque properly applied (as with ALL the other times I have ever changed my wheels). I even bought another calibrated torque wrench to double check.

 

I had found a thread that had listed other similar failures on very closely related models on another board. VERY TROUBLING PATTERN HERE!

http://www.subaruoutback.org/forums/66-problems-maintenance/25711-breaking-wheel-studs.html

 

It was in describing my THIRD failure that someone mentioned that I could be UNDER torquing my lugs. I decided to do a little homework and in fact found that the original 2005/2006 Subaru FSM in four separate sections incorrectly lists the lug nut torque at 66 ft-lbs when it should be 81.1 ft-lbs. The incorrect spec is what I have been following more and more stringently as my paranoia of over torquing has grown. How ironic that the tire shop monkey with his torque stick was likely doing better for my car than my fanatical torque wrench tweaking.

 

Digging further I found that Subaru issued a correction http://techinfo.subaru.com/proxy/10156/pdf/18-97-06104073.pdf in the entry fourth from the bottom on page 1. I would also suspect that other '05 and '06 failures I have read about on various forums are due to the same error. Another lesson learned is to check for manual changes and repurchase the changed sections on a regular basis. Although I doubt there are many other torque settings that as critical as this.

 

After researching more, I found that indeed under torquing is a leading cause of stud failure (which I never really thought about). I found this article very informative on the matter; http://www.metalconsult.com/articles/Wheel%20Stud%20Bolt%20Failures.pdf

 

So there you have it. I believe I have come to a conclusion. My plan forward is to again replace all 20 studs (boy that hydraulic press was a good investment) and hopefully put this whole thing behind me.

 

Hopefully this proves useful to others

 

I am entering this discussion as I have a 2005 Legacy Wagon. I have owned it since new. I have always done all of the work on it. Although now retired, I worked for 30 years at an electric utility as a mechanic, and held ASE Auto and Truck master certifications, so I should be qualified to do the work, eh?

 

At about 75,000 miles or so I discovered a broken stud (on the right rear) and found several nuts missing (2 additional missing on the same right rear, one on the left rear and one on the right front). I immediately replaced all of the studs and nuts with new from the Subaru parts department where I bought the car, and inspected the wheels and lug nut seats.

 

Since then the nuts won't stay tight.

 

I have always used a torque wrench to tighten the nuts (to 82ftlbs) after running them down evenly by hand with a socket on a t-handle.

 

At about 105,000 miles one of the bearing hub assemblies failed, and I replaced all four corners. Now, with about 8,000 miles on the new hubs (also OEM) I have another broken stud on the right rear, and the nuts still refuse to stay tight.

 

The wheel and rotor surfaces are clean (I clean them with a wire brush every time I have the wheels off), and the threads on the studs are also kept clean with a clean wire brush. Since I have my torque wrenches checked for accuracy every year or so, the torque applied to the studs and nuts should be accurate. I rotate the tires every time I change my oil (5,000 miles), so a problem with the wheel shouldn't be suspect for the broken right rear studs.

 

I just don't get it.

 

I have a 1971 Datsun 240Z that has been a production based road race car since 1979. In 1990 I replaced the wheel studs (I use wheel studs from the Datsun pickups from the same era, as they are the same thread, but a bit longer to facilitate use of wheel spacers) as a matter of course, since it gets thrashed pretty hard on the track. I use Ansen and US Indy slotted aluminum wheels, with shouldered lug nuts. The wheels are taken off and on about 10 to 15 times every race weekend, and numerous times over the course of the racing season during the between race weekend thrash.

 

Not once have I experienced a wheel stud failure or loose lug nuts.

 

So how is it that my Subaru has become so problematic?

[rob]

Yeah, that sucks, sorry to hear. One idea that came up during my trials that I did not follow up on was the lugnuts themselves. It is possible that the acorn style lugnuts are bottoming out on the stud. It wouldn't be too difficult for you to try open style nuts on one side and see if they stay put better compared to the other side.

 

My other question for you since you didn't mention it is, after you install the wheel. Do you go back and retorque after your first drive? I find that after things settle, there are always a couple that need to be retorqued.

 

For me, My LGT is at 160k now and I think I now have these issues behind me. I sent my broken parts for a failure analysis by the expert (Metallurgical Consulting) responsible for the report that I linked before. He looked at two of my stud failures and concluded the failure was *most certainly* metal fatigue. After discussing my experience and suspicions he agreed that under torquing (thanks to the type-o in the FSM) was the likely cause. Further more, he was very clear to stop worrying about over torquing (as the margin of error on the high side is pretty wide) and stay away from the low end of the spec.

 

From his recommendations my new regimen is every year or two (or as needed) I clean all of the stud threads and apply new anti-seize. I final torque to 80ft-lbs which, with the thread lube, puts me at about 20% over the intended torque. I remove my wheels for snow tire swaps least 2 or 3 times a season plus as needed for any car work. It is impossible to know if the problem is solved completely, but I have gone from several failures in a short span down to zero if the past 2 1/2 years.

 

 

-Rob

[RacerX69]

My other question for you since you didn't mention it is, after you install the wheel. Do you go back and retorque after your first drive? I find that after things settle, there are always a couple that need to be retorqued.

 

Yep.

 

It has been my habit to go around after 50 miles or so and check them on all my vehicles since my first car.

 

So.

 

I've been experimenting, sort of, since last February. The first time I serviced my Legacy after the last post here I cleaned the hubs, rotors, studs, lugnuts and wheels. Then I coated all the mating surfaces with anti-seize compound, a very thin film, a little goes a long way. I made sure to keep the threads clean and dry.

 

The car has been on my lift for oil/filter/inspection/tire rotation 3 times, and once for new brakes. Each time the mating surfaces are wiped with a clean rag, inspected, and a fresh film of anti-seize applied.

 

Each time I checked the torque after 50 to 100 miles and the lugs have been tight at each check. Before removing lugs for service or repair I have been checking and things have been OK.

 

I think the key has been keeping the stack up of hub/rotor/wheel clean. The anti-seize prevents corrosion.

 

Problem solved?

 

Maybe.

[Suby02]

In the past 14 months I have since had two additional stud failures since this incident.

 

Quick recap; '05 LGT wagon owned since new 120k miles

 

July '10 : Wheel falls off RR while driving down the highway. All 5 studs sheared off. Replaced all 10 front studs with OE; replaced both rear bearing/hubs (comes with new studs) replaced RR brake rotor. Replaced RR lug nuts.

 

July '11: While checking lug nut torque one stud on the LR snaps off with very little effort. Replaced all rear studs with non-OE, made in USA parts. Replaced LR rotor.

 

Aug'11: Again, while checking torque one stud on the RR snaps off with almost NO effort. I had exactly one wheel off/on cycle for a brake job, a little over a month and maybe 1k miles on these NEW studs!! I did the work myself. Torque properly applied (as with ALL the other times I have ever changed my wheels). I even bought another calibrated torque wrench to double check.

 

I had found a thread that had listed other similar failures on very closely related models on another board. VERY TROUBLING PATTERN HERE!

http://www.subaruoutback.org/forums/66-problems-maintenance/25711-breaking-wheel-studs.html

 

It was in describing my THIRD failure that someone mentioned that I could be UNDER torquing my lugs. I decided to do a little homework and in fact found that the original 2005/2006 Subaru FSM in four separate sections incorrectly lists the lug nut torque at 66 ft-lbs when it should be 81.1 ft-lbs. The incorrect spec is what I have been following more and more stringently as my paranoia of over torquing has grown. How ironic that the tire shop monkey with his torque stick was likely doing better for my car than my fanatical torque wrench tweaking.

 

Digging further I found that Subaru issued a correction http://techinfo.subaru.com/proxy/10156/pdf/18-97-06104073.pdf in the entry fourth from the bottom on page 1. I would also suspect that other '05 and '06 failures I have read about on various forums are due to the same error. Another lesson learned is to check for manual changes and repurchase the changed sections on a regular basis. Although I doubt there are many other torque settings that as critical as this.

 

After researching more, I found that indeed under torquing is a leading cause of stud failure (which I never really thought about). I found this article very informative on the matter; http://www.metalconsult.com/articles/Wheel%20Stud%20Bolt%20Failures.pdf

 

So there you have it. I believe I have come to a conclusion. My plan forward is to again replace all 20 studs (boy that hydraulic press was a good investment) and hopefully put this whole thing behind me.

 

Hopefully this proves useful to others

[Suby02]

In the past 14 months I have since had two additional stud failures since this incident.

 

Quick recap; '05 LGT wagon owned since new 120k miles

 

July '10 : Wheel falls off RR while driving down the highway. All 5 studs sheared off. Replaced all 10 front studs with OE; replaced both rear bearing/hubs (comes with new studs) replaced RR brake rotor. Replaced RR lug nuts.

 

July '11: While checking lug nut torque one stud on the LR snaps off with very little effort. Replaced all rear studs with non-OE, made in USA parts. Replaced LR rotor.

 

Aug'11: Again, while checking torque one stud on the RR snaps off with almost NO effort. I had exactly one wheel off/on cycle for a brake job, a little over a month and maybe 1k miles on these NEW studs!! I did the work myself. Torque properly applied (as with ALL the other times I have ever changed my wheels). I even bought another calibrated torque wrench to double check.

 

I had found a thread that had listed other similar failures on very closely related models on another board. VERY TROUBLING PATTERN HERE!

http://www.subaruoutback.org/forums/66-problems-maintenance/25711-breaking-wheel-studs.html

 

It was in describing my THIRD failure that someone mentioned that I could be UNDER torquing my lugs. I decided to do a little homework and in fact found that the original 2005/2006 Subaru FSM in four separate sections incorrectly lists the lug nut torque at 66 ft-lbs when it should be 81.1 ft-lbs. The incorrect spec is what I have been following more and more stringently as my paranoia of over torquing has grown. How ironic that the tire shop monkey with his torque stick was likely doing better for my car than my fanatical torque wrench tweaking.

 

Digging further I found that Subaru issued a correction http://techinfo.subaru.com/proxy/10156/pdf/18-97-06104073.pdf in the entry fourth from the bottom on page 1. I would also suspect that other '05 and '06 failures I have read about on various forums are due to the same

 

 

error. Another lesson learned is to check for manual changes and repurchase the changed sections on a regular basis. Although I doubt there are many other torque settings that as critical as this.

 

After researching more, I found that indeed under torquing is a leading cause of stud failure (which I never really thought about). I found this article very informative on the matter; http://www.metalconsult.com/articles/Wheel%20Stud%20Bolt%20Failures.pdf

 

So there you have it. I believe I have come to a conclusion. My plan forward is to again replace all 20 studs (boy that hydraulic press was a good investment)

 

and hopefully put this whole thing behind me.

 

Hopefully this proves useful to others

 

Yes rob , your post is very useful! Thank you thank you thank you

 

My O2 legacy gt wagon has 144k

 

1-About 130k , I started to notice missing lug nuts ... first a right rear

Wheel, then a second and third nut with matching flat off sheared stud level to rim over the course of an additional 5 k on the same rear wheel . When shop replaced stud, they said another stud broke!

I blame the issue on my handtorquing a tire change " too tight " I also had rechecked torque very hand tight after a 100 mile retorque.

My diagnosis is " I set them too tight ". I know they were tight and not undertorqued.

 

I think this is weird.

 

2: about 133 k , I replace rotors and pads on front. Set front nice and tight. Left front wheel gets loose, daughter is driving to get home, left wheel jams in well .broken stud and loose nuts. Alloy wheel studs holes are oval. Plus fractured stud and another missing nut on left rear wheel.

My diagnosis:

Undertorqed

 

3: I take car away from daughter, this thing is dangerous!

 

4: I pay shop to replace 20 studs. I rechecked the shop torque using the index method , the shop set torque at 90 foot pounds

5:about 5k later I got another fractured stud on the left rear!

[rob]

As an update since my last post, my LGT now has 194k miles. I have not had any additional problems. Nothing else has changed other than occasionally cleaning and lubing the studs with anit-sieze and torquing at 80ft-lbs (without correcting for the lube).

[tumbleweed 49]

Somewhat related question. How can we get our torque wrenches checked? I have three of them and they have never been checked or calibrated after years of use.