5 sheared studs and the wheel falls off...

[rob]

UPDATE 9-17-11:

 

In the past 14 months I have had two additional stud failures since this incident. I believe I figured out the source of my problems. To make a long story short, 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. This is the spec I have been following. It is my conclusion that serious under torquing of my lugs caused cyclical fluctuating loads that lead to premature fatigue cracking and ultimate failure. I will add more details in new posts.

 

>>>>>>>>>>

 

 

So.....how does this happen?? My wife, 2-kids, sister-in law and my nephew today were traveling from Montana to Seattle. About 10 hrs into the trip heading over the mountain pass and BOOM tire falls off and jams up into fender. They were in a short tunnel when it stalled out. Thankfully they were able to limp it the 100feet or so out and onto the shoulder without getting smashed by a semi.

 

I took a good look at it when the tow truck got it home and I am really at a loss to explain it. Before they left a week ago, I double checked all the torque values. A day or so ago they washed it and didn't notice any miss lug nuts. At first I thought it had to be that the nuts just fell off on the way and the studs just eventually gave out. However they reported zero noise or vibration, just a sudden smash. The stud holes in the wheel looked pretty clean, so no evidence of any serious wobbling.

 

It's an '05 LGT wagon with ~105k miles. Stock all the way around. We have owned it since new and I am religious about torquing things proper. I say that I change my tires 5 or so times a year off and on with snows (maybe 10 times this year with the extra ski trips), so probably a little more than average. Right now it looks like a catastrophic failure of the studs. I can't think of anything else. Tomorrow I will talk with the Subaru and the Insurance company. I did a quick search and didn't see any other reported failures.

 

I'm curious if you guys have any other thoughts as to how this could have happened.

 

-Rob

[LosAngelesLGT]

Wow, just wow. Sorry Rob... PICS? WOW... Glad no one was smashed by a semi!!! "in a tunnel"!!!

[rob]

As a matter of fact I do....

 

http://lh5.ggpht.com/_Tmouzv-_cmI/TDq3IuBEtAI/AAAAAAAAB8k/1ZuNyGBsDGg/s800/DSC_2051.JPG

 

http://lh4.ggpht.com/_Tmouzv-_cmI/TDq3bHLdzBI/AAAAAAAAB8o/EduFVQ8LKLg/s800/DSC_2052.JPG

 

http://lh4.ggpht.com/_Tmouzv-_cmI/TDq3iXOIGVI/AAAAAAAAB84/aSs2-Q2JVDI/s800/DSC_2054.JPG

[LosAngelesLGT]

Wow thats just CRAZY! Your car is in clean shape too. Not all eaten from east coast salt/snow roads... WOW! That is freaking scary. Good thing it was the rear!!!

[Max Capacity]

Why is the inside of the wheel all black ?

 

Glad everyone made it out safely.

[BAC5.2]

I have honestly never seen that before. Wow.

 

What did you torque them to?

[Blue GT]

Thankfully no one was hurt. That's just crazy, to have everything torqued ok, then just bam loose a wheel.

[Legend]

Wow! ;(

[FredBeans]

Do you anti-seize the lug studs? If so you need to lower your torque spec... -15% is the rule-of-thumb I use.

 

Over-torquing and multiple cycles per year could definitely lead to this failure and I would be weary of the other three corners.

[rob]

Yeah thanks guys. Indeed it could have been a whole lot worse. Not the best way to spend a sunday evening. No I don't anti-seize the family wagon. After changing several stripped studs, I do use the goo on my Impreza. With rallyx I change tires a lot more on that guy and yes I do use a lower torque value(which does get the lower torque value). On the Legacy the last torque was 70 ft-lbs.

 

And yeah, I am worried about the other rear corner now too. The fronts had wheel bearings changed under warranty at about 50k miles so at least those studs won't be from the same batch (hopefully)....

 

-Rob

[mustangendsley]

From the looks of the back of the rim from were the bolts go through, that rim was moving a lot side to side. It is wird to see the studs striped almost the same lenght also. I'd say your lugs came loose and thats all she wrote, maybe some kids came by and loosened them up?

[rob]

The back face of the wheel got chewed up, but I'm pretty sure that was from limping the car off the road. The wheel wasn't turning, but the hub still was. I need to spend more time studying the wheel lug holes, but on first glance there was no indication of any marks inside the holes or on the front seats. And like I said, there was zero wobble or noise before it gave way. It's hard to see how the nuts could have fallen off and had none of those symptoms. If it hadn't been in a freakin tunnel, I would drive back up there and go fishing for the broken parts. It would be very interesting to find the end of those studs with the nuts on them....

[TSiWRX]

Damn, that's CRAZY!!!!

 

Glad no-one was hurt!

[whitetiger]

man you are lucky. it could have been this.

 

[ame=http://www.youtube.com/watch?v=jv4m41viy4I]YouTube- RX7 wheels fall off[/ame]

[GTTuner]

Those must have been left loose at one time or at the time. That is the ONLY time I have ever seen all the studs snap. Get a close up snap shot of the lug holes for me.

[SubLo]

Metal fatigue + really quick sequential failure. I'm hypothesizing but perhaps due to frequent changing, mileage and maybe even inferior stud grade/metal and/or manufacturing tolerances, a couple of extra thousands wore on the hub creating a bit of extra stress on the lugs. Over time/bumps/load, the studs fatigued enough until whammo.

[BAC5.2]

That RX7 video is one of my favorites. Poor guy.

 

Do you use wheel locks? I wonder if someone DID loosen them (possibly in an effort to steal the wheels for new tires). They loosened all 4, got to the 5th one, couldn't get the wheel lock off, then just hand-threaded the other 4 back on and ran off.

 

It's easy to tell if you have only a few lugs holding the front wheel on. You can feel it in the wheel. It's more difficult if it's a rear wheel AND you have a full load of people/gear in the car.

 

Are you the only one who has ever removed/installed wheels on the car? That is another possibility. When I got my old Forester inspected, the shop pulled the left-rear wheel off to inspect the brakes. They hand-threaded the lugs back on and forgot to torque them down. I drove off. For some reason, the next day, I wanted to do a tire rotation. I got to the back left corner, and 2 lug nuts were missing, and the studs were chewed up. I'm pretty sensitive to noises and vibrations, and I don't recall noticing anything extreme. Had I driven more, I could have had the same result.

[TSiWRX]

^ Both very possible scenarios....

 

Of the last, I also had such an encounter a few years ago (tire replacement). The shop's manager and owner both got an earfull.

[rob]

http://lh5.ggpht.com/_Tmouzv-_cmI/TDtS_kk3EcI/AAAAAAAAB9Q/rMm37_X8HBs/s800/071110b.jpg

 

 

http://lh4.ggpht.com/_Tmouzv-_cmI/TDtS84XhH3I/AAAAAAAAB9M/aogoCbUOPYQ/s800/071110a.jpg

[rob]

That RX7 video is one of my favorites. Poor guy.

 

Do you use wheel locks? I wonder if someone DID loosen them (possibly in an effort to steal the wheels for new tires). They loosened all 4, got to the 5th one, couldn't get the wheel lock off, then just hand-threaded the other 4 back on and ran off.

 

It's easy to tell if you have only a few lugs holding the front wheel on. You can feel it in the wheel. It's more difficult if it's a rear wheel AND you have a full load of people/gear in the car.

 

Are you the only one who has ever removed/installed wheels on the car? That is another possibility. When I got my old Forester inspected, the shop pulled the left-rear wheel off to inspect the brakes. They hand-threaded the lugs back on and forgot to torque them down. I drove off. For some reason, the next day, I wanted to do a tire rotation. I got to the back left corner, and 2 lug nuts were missing, and the studs were chewed up. I'm pretty sensitive to noises and vibrations, and I don't recall noticing anything extreme. Had I driven more, I could have had the same result.

 

Nope, no wheel locks. I thought about someone monkeying with the car. They did make a stop about 4hrs earlier in the drive and left the car, but it was at a big park on a busy street. I even asked if they pissed anybody off on the interstate that could have followed them to a rest stop. Still, hard to believe they could drive that far and not feel it. Trust me, when my wife notices ANYTHING out of the ordinary with the car I hear about it first

 

 

But I agree on the rear in a fully loaded car (the trunk was packed tight) it would be harder to notice. The only time I forgot to tighten the lugs several years ago it was DAMN obvious when the wheel was about to fall off, but that was on the front.

 

Nope I am the only one who changes the wheels. And I haven't had them off for a couple months.

[rob]

Metal fatigue + really quick sequential failure. I'm hypothesizing but perhaps due to frequent changing, mileage and maybe even inferior stud grade/metal and/or manufacturing tolerances, a couple of extra thousands wore on the hub creating a bit of extra stress on the lugs. Over time/bumps/load, the studs fatigued enough until whammo.

 

Yep that's my guess as well. If that is all correct....it is a completely unacceptable failure.

[TSiWRX]

^ +1, that's just plain scary........

[rob]

So I called Subaru and reported the incident. I was not thrilled with the response. Essentially they took the report and basically said that they probably won't follow-up since it was a customer reported incident. They would take it more seriously if it comes from the insurance company or a dealer. I thought at the very least they would want to send someone out to take a look before the car is touched. I didn't get the sense that they were all that concerned. I guess what they really need is for the delear's oil change expert to weigh in with his opinion on metal fatigue......

[rob]

Those must have been left loose at one time or at the time. That is the ONLY time I have ever seen all the studs snap. Get a close up snap shot of the lug holes for me.

 

Not the best shot, but looks to me like the seating surface and bore hole are clean and smooth. The dingleberries looking through the hole are from the where the backside got chewed up.

 

http://lh4.ggpht.com/_Tmouzv-_cmI/TDtYO60t0jI/AAAAAAAAB9g/4oTYEj9QBNo/s800/071110d.jpg

[rob]

And when I say chewed up.....

 

http://lh6.ggpht.com/_Tmouzv-_cmI/TDtZIqgoyKI/AAAAAAAAB9w/W6RQv0rhBWM/s800/071110.jpg